#arthrobacter

[biology-geology-beaches-india]

The Science Research Notebooks of S. Sunkavally. Page 297.

[captaindomy]

Article: Inoculation of Arthrobacter sp. improves the growth of Acanthocalycium sp. and the fruits nutraceutical quality and the flowers longevity

Author: Domenico Prisa * CREA Research Centre for Vegetable and Ornamental Crops, Council for Agricultural Research and Economics, Via dei Fiori 8, 51012 Pescia, PT, Italy.Research Article GSC Biological and Pharmaceutical Sciences, 2024, 29(01), 117–123.Article DOI: 10.30574/gscbps.2024.29.1.0370DOI url: https://doi.org/10.30574/gscbps.2024.29.1.0370Publication history:Received on 28 August…

[scienza-magia]

Superbatteri creati nella stazione spaziale

I batteri sulla Stazione spaziale internazionale stanno mutando. L’analisi del genoma svela come i microrganismi si stiano adattando alla vita in orbita, rafforzando anche alcuni tratti patogenici. Ovunque ci siano essere umani ci sono anche batteri. Ce li portiamo dietro, è inevitabile. Ed è così che microrganismi che si sono evoluti con noi sulla Terra hanno “conquistato” anche lo Spazio, e si stanno adattando. Lo confermano le ricerche degli scienziati del Jet propulsion laboratory della Nasa, che da un decennio circa raccolgono e analizzano campioni dalla Stazione spaziale internazionale (Iss) per monitorare i cambiamenti e assicurarsi che non ci siano minacce per gli astronauti in orbita. Ecco cosa hanno scoperto finora. Batteri a confronto I ricercatori hanno isolato molte specie batteriche dai campioni prelevati in diversi ambienti della Iss - specie che, ovviamente, esistono anche sulla Terra. Mettendo il materiale genetico a confronto, però, hanno notato che i microbi che hanno vissuto nella bassa orbita terrestre si stanno differenziando dai loro parenti sul pianeta natale, sviluppando adattamenti che li aiutano a sopravvivere in condizioni estreme. Nel loro ultimo lavoro, Kasthuri Venkateswaran e colleghi hanno studiato specie batteriche scoperte sulla Iss di recente, in particolare Microbacterium mcarthurae, Microbacterium meiriae, Paenibacillus vandeheii, Arthrobacter burdickii e Leifsonia williamsii. Questi microbi - sostengono i ricercatori - hanno sviluppato caratteristiche comuni tra di loro, ma diverse da quelle degli stessi batteri sulla Terra. Si sono adattati alla vita nello Spazio modificando alcune proteine così da renderle più funzionali in condizioni di microgravità e il loro sistema di riparazione del dna è più attivo per contrastare gli effetti dell’aumentata esposizione alle radiazioni. Inoltre, gli scienziati hanno osservato la presenza di elementi genetici mobili che ne hanno migliorato il metabolismo. I batteri spaziali mutanti sono una minaccia? A destare in modo particolare l’attenzione degli esperti, però, è il fatto che nelle specie batteriche vissute sulla Iss siano emersi tratti genetici collegati a potenzialità patogene: alcuni geni associati alla virulenza (come quelli che aiutano a eludere o danneggiare il sistema immunitario) sono più attivi. In più, sembra che i microbi spaziali siano in grado di costituire dei biofilm sulle superfici della Iss - capacità che li rende più resistenti ai disinfettanti e agli antibiotici. Se ad oggi ciò rappresenti un rischio concreto per la salute degli astronauti non è ancora chiaro (non c’è comunque nessun allarme), ma si conferma come studiare gli adattamenti dei microbi allo Spazio sia di estrema importanza in previsione di viaggi spaziali di lunga durata. Innanzitutto ora siamo consapevoli come sia necessario mettere in pratica azioni più incisive per prevenire la proliferazione dei batteri sulle superfici (per esempio controllare meglio l’umidità degli ambienti sulla Iss); poi, quelle stesse mutazioni potrebbero diventare bersaglio per nuovi farmaci, qualora i batteri modificati si rivelassero un rischio per la salute. Ma - concludono gli scienziati - potremmo anche scoprire che questi superbatteri sono una risorsa. Read the full article

[moleculardepot]

Choline Oxidase from Arthrobacter globiformis

Choline Oxidase from Arthrobacter globiformis Catalog number: B2017880 Lot number: Batch Dependent Expiration Date: Batch dependent Amount: 100 Units Molecular Weight or Concentration: N/A Supplied as: Powder Applications: a molecular tool for various biochemical applications Storage: -20°C Keywords: Choline: oxygen 1-oxidoreductase Grade: Biotechnology grade. All products are highly pure. All…

[skretting2024]

Enhancing Fish Performance: The Power of Aquaculture Probiotics

In aquaculture, maintaining optimal fish health is crucial for sustainable farming practices. Probiotics have emerged as key players in achieving this goal, offering a natural and effective way to promote gut health and overall well-being in fish. Skretting fish feed, known for its high quality and nutritional value, often incorporates these beneficial probiotics. In this comprehensive guide, we delve into the world of aquaculture probiotics, exploring their types, mechanisms of action, and their indispensable role in enhancing fish performance.

Probiotics:

●      Defined as beneficial bacteria and yeasts that support a healthy gut and immunity in fish.

●      Commonly consisting of various bacterial species like Arthrobacter, Bacillus, and Vibrio, alongside yeast species such as Saccharomyces cerevisiae.

●      Bacillus spp. stands out as the most prevalent bacterial probiotic, while Saccharomyces cerevisiae is a commonly used yeast in aquaculture.

Prebiotics:

●      Substances that fuel the growth and activity of probiotics in the fish's digestive system.

●      Essential for optimizing the therapeutic effects of probiotics and promoting a balanced gut ecosystem.

Para probiotics:

●      Non-viable or inactivated forms of beneficial bacteria that still confer health benefits to fish.

●      Serve as alternative options for probiotic supplementation, offering similar advantages without the need for live organisms.

Synbiotics:

●      A powerful combination of probiotics and prebiotics that synergistically enhance fish health and performance.

●      Work hand in hand to bolster gut health, immunity, and overall well-being in aquatic species.

Metabiotics:

●      Derived from metabolic processes of living organisms, metabiotics refer to compounds with potential beneficial effects on fish health.

●      Offer a natural and sustainable approach to supporting fish well-being, harnessing the power of biological processes.

Mechanisms of Action:

●      Competitive exclusion: Probiotics produce inhibitory compounds to outcompete harmful pathogens.

●      Nutrient competition: Compete for resources, limiting the growth of pathogens.

●      Adhesion site competition: Prevent pathogen attachment, reducing the risk of infections.

●      Digestive contribution: Aid in digestion and nutrient absorption, promoting optimal growth.

●      Immune enhancement: Stimulate immune responses, fortifying fish against diseases.

●      Quorum sensing manipulation: Reduce pathogen virulence, further enhancing fish resilience.

Conclusion:

Incorporating probiotics into aquaculture practices offers a natural and effective means of promoting fish health and performance. By understanding their types and mechanisms of action, aquaculturists can optimize their use to create a balanced and resilient ecosystem. Embracing probiotics not only enhances fish welfare but also contributes to the sustainability of aquaculture operations.

[kisan4u]

Growth Boosters: How Bio-Fertilizers are Changing Organic Agriculture

Organic farming is gaining popularity. This practice once started from house gardens but has been forced to professional farms due to the increasing preference for organic products among consumers. The idea of organic farming has grown over time. It initially involved the use of organic waste in the form of manure and compost to grow plants in a sustainable environment while boycotting synthetic fertilizers. However, at present times organic farming focuses on the basics of plant growth to reap long-term sustainable benefits. This has coined a new term i.e. bio-fertilizers widely used and hence actively commercialised. So, hurry up and order your bio-growth organic fertilizers now.

How do bio-fertilizers work?

Despite their name and classification, bio fertilizers are not fertilizers but microorganisms that promote plant growth. Bio-fertilizers indirectly enhance plant growth by utilizing microorganisms to enhance natural processes in the soil to affect plant growth. Different bacteria induce different biological activity in the ground. Thus, choosing what works best for your soil and crops is essential to the choice of bio-fertilizers.

Types of bio-fertilizers

Nitrogen- Fixing bio-fertilizers

These microorganisms convert atmospheric nitrogen into ammonia which is utilized by the plants. The process is known as nitrogen fixation. There are three types of nitrogen-fixing bacteria namely free-living nitrogen-fixing bacteria, associative symbiotic nitrogen-fixing bacteria, and symbiotic nitrogen-fixing bacteria.

Phosphate Solubilizing Bio-fertilizers

Phosphate Solubilizing Microorganisms (PSMs) are used for the process of converting phosphorus compounds into water-soluble formats to lower soil’s pH and make it easier for the plants to absorb it. Bacillus megaterium, Bacillus circulans, Pseudomonas striata, Penicillium, and Aspergillus are examples of PSMs.

Phosphate Mobilizing Bio-fertilizers

Phosphate mobilizing bio-fertilizers contain mycorrhizal fungi that act as phosphate absorbers. Arbuscular mycorrhizal fungi (AMF) and Ectomycorrhizal (ECM) fungi are the two major types of mycorrhizae for bio-fertilizers.

Bio-fertilizers for Micronutrients

Some essential micronutrients include boron, chlorine, copper, iron, manganese, molybdenum, zinc, and nickel, but these are found in trace amounts in plant tissues. So, bio-fertilizers are required to promote the utilization of these nutrients. Micronutrient bio-fertilizers are potentially cheaper alternatives to traditional fertilizers such as zinc sulfate.

Plant Growth- Promoting Rhizobacteria

These bio-fertilizers utilize rhizobacteria or microbes that naturally occur in the rhizosphere of the soil, allowing them to conduct their natural processes associated with plant growth. Achromobacter, Actinoplanes, Agrobacterium, Alcaligenes, Amorphosporangium, Arthrobacter, Azotobacter, Bacillus, Bradyrhizobium, Cellulomonas, Enterobacter, Erwinia, Flavobacterium, Rhizobium, Streptomyces and Xanthomonas are some of the commonly found PGPRs.

Compost Bio-fertilizers

Compost is a mixture of decomposed plant and food waste that breaks down into nutrient-rich fertilizers. The breakdown of organic matter is dependent on factors like temperature, moisture, and oxygen and is time-consuming. The process is accelerated by the addition of organisms like worms, fungi, and bacteria. Such organisms are known as compost bio-fertilizers.

Advantages of Bio-fertilizers

· Bio-fertilizers boost plant growth and increase crop yield

· Since bio-fertilizers are organic material they increase overall soil health over time.

· They are economical in comparison to traditional fertilizers

· As bio-fertilizers work on improving the overall plant growth ecosystem, they maintain an ideal growth rate despite harsh climates or unfavorable weather conditions. 

· They control and inhibit pathogenic soil bacteria.

· They are eco-friendly and pollution-free.

Products Containing Bio-fertilizers

Some of the best organic fertilizers for plants online are made available by brands like Kisan4u, Virus-G, Miticide, Katra, Atal, ZINCOTAC, PROSPER, Keprine, BIO-RINGA, HUMUS 100, Pyrroloquinoline Quinone Novel Enzymes & Vitamines, CLASSIC.

Buy your Bio-Fertilizers Online

Why wait to eradicate the source of all problems? Organic fertilizers online shopping is now available on kisan4u.com. So, hurry up and order your set of bio-fertilizers now. 

[softwater3452]

If I Boil Faucet Water For 20 Minutes, Would It Not Be Sufficiently Dechlorinated For My Fish Tank?

Since then, I've been a marine biologist at That Fish Place - That Pet Place, together with a Fish Room supervisor, copywriter, livestock inventory controller, livestock mail-order supervisor and other duties right here and there. I additionally spent eight seasons as knowledgeable actress with the Pennsylvania Renaissance Faire and in different dechlorinators palm beach local roles. If that isn't dangerous enough, I'm a proud Crazy Hockey Fan (go Flyers and go Hershey Bears!). I would advocate silk over plastic since they are typically softer but there shouldn’t be any problems with artificial crops and bettas.

I would recommend avoiding ivy and sticking with some more aquatic-friendly plants like these really helpful right here. Hi Hannah, It is perfectly normal for a betta to hide in a plant or another ornament. Assuming that you just don’t have it in a tank with different fish that might dechlorinators palm beach be harassing it, it's in all probability just snug there. Hello Sonya, It is tough to say with out understanding what plant you're referring to, however I wouldn’t suggest placing any land crops in an aquatic surroundings.

Diuron was discovered to be mineralized in buffer strip soil and in the sediments of the Morcille river in the Beaujolais vineyard repeatedly handled with this herbicide. Evidence for cooperative mineralization of diuron by Arthrobacter sp. SP1 isolated from a combined culture enriched from diuron exposed environments. Isolation and characterization of aerobic culturable arsenic-resistant bacteria dechlorinators palm beach from surfacewater and groundwater of Rautahat District, Nepal. Chemical modeling of groundwater within the Banat Plain, southwestern Romania, with elevated As content material and co-occurring species by combining diagrams and unsupervised multivariate statistical approaches. Comparison of direct-plating and broth- enrichment culture methods for detection of potential bacterial pathogens in respiratory secretions.

[biology-geology-beaches-india]

The Science Research Manuscripts of S. Sunkavally. Page 286.

[delifoodsmanufacturer]

The Sugar Of Life---Trehalose

Trehalose is known as "The sugar of life" Trehalose was first extracted from the ergot fungus of rye by Wiggers et al in 1832, and then the French chemist Berthelot discovered the sugar from the molasses secreted by a weevil, which may be more algae. The reason is named trehalose; studies have found that trehalose is widely found in many edible animals, plants and microorganisms in nature, such as beans, shrimp, bread, beer and yeast fermented foods that are eaten in life. Trehalose, which is widely found in fungi, algae, mosses, and invertebrates, is also known as "the sugar of life". The industrial production of trehalose has gone through three stages: microbial extraction method, microbial fermentation method, and enzyme synthesis method. At the beginning, trehalose was extracted by the extraction method, and the price was extremely high. Until 1992, the Japanese Hayashibara Co., Ltd. Sugar scientist Kazuhiko Maruta discovered that Q36, a soil bacterium from the genus Arthrobacter, produces two enzymes. These two enzymes, together with the starch-degrading enzyme discovered in 1966, repeatedly react with maltodextrin to produce trehalose. Afterwards, trehalose is produced in large quantities by various methods such as fermentation yeast, Grifola frondosa cell extraction or enzymatic conversion of starch. China has been producing trehalose industrially since 2000. At present, it is produced by enzymatic synthesis, using glucose, maltose or starch as substrates, decomposed into short-chain dextrins by exclusive enzyme preparations, and then converted into trehalose by the action of trehalose synthase. So trehalose is an industrial sweetener, not derived from seaweed. Trehalose is a common food raw material Trehalose has very good stability to heat and acid-base, and Maillard reaction does not occur when heated. At present, this sugar is widely used in food, biomedicine, agriculture, cosmetics and other fields. Because of its stable nature, it can be added during food processing to prolong the shelf life of food, inhibit protein denaturation, and maintain food flavor. Add to. Trehalose is actually a common food ingredient, and it has been approved for use in many countries many years ago: - In October 2000, the U.S. Food and Drug Administration (FDA) granted trehalose GRAS (Generally Recognized as Safe) status and approved to enter the U.S. food field; - In November 2000, the Joint Expert Committee on Food Additives (JECFA) of the Food and Agriculture Organization of the United Nations and the World Health Organization (JECFA) confirmed that there is no need to limit the allowable daily intake (ADI) of trehalose; - On September 25, 2001, the European Union approved trehalose to enter the market as a new type of food or food ingredient; - Around 2000, Canada, South Korea and other countries and regions also approved trehalose for use in food, some as food raw materials, and some as food additives; - The industry standard for trehalose was jointly drafted by Nanning Zhongnuo Bio and the China Food and Fermentation Industry Research Institute in 2007, and the national recommended standard for trehalose in 2009 was GB/T 23529-2009; - In 2014, the National Health Commission of China also approved trehalose as a common food raw material, which can be added to various foods. Read the full article

[valgasnewsthings]

Contents

Microbiology

Vol. 91, No. 3, 2022

A simultaneous English language translation of this journal is available from Pleiades Publishing, Ltd. Distributed worldwide by Springer. Microbiology ISSN 0026-2617.

Reviews

The Lut Desert and Its Microbial Diversity: Recent Studies and Future Research

M. S. Shirsalimian, S. M. Mazidi and M. A. Amoozegar p. 215  abstract

Experimental Articles

A New Glance on the Mechanism of Autotrophic CO2 Assimilation in Green Sulfur Bacteria

R. N. Ivanovsky, N. V. Lebedeva and T. P. Tourova p. 225  abstract

Genomic and Physiological Characterization of Halophilic Bacteria of the Genera Halomonas and Marinobacter from Petroleum Reservoirs

T. P. Tourova, D. S. Sokolova, E. M. Semenova, A. P. Ershov, D. S. Grouzdev and T. N. Nazina p. 235  abstract

Genetic Determinants of Xylan Utilization in Humisphaera borealis M1803T, a Planctomycete of the Class Phycisphaerae

D. G. Naumoff, I. S. Kulichevskaya and S. N. Dedysh p. 249  abstract

Cell Wall Glycopolymers as a Diagnostic Trait of Arthrobacter crystallopoietes

N. V. Potekhina, E. V. Ariskina, A. S. Shashkov, T. M. Tul’skaya and L. I. Evtushenko p. 259  abstract

Effect of Epinephrine, Norepinephrine, and Estradiol on Persister Formation in the Cultures of Staphylococci from the Human Microbiota and Their Resistance to Starvation and New Medium Stresses

T. A. Pankratov, Yu. A. Nikolaev, A. V. Gannesen and G. I. El’-Registan p. 267  abstract

The Effects of Lactic Acid Bacteria on Salmonella Biofilms

Ş. Göksel, N. Akçelik, C. Özdemir and M. Akçelik p. 278  abstract

Effect of Carbon Nanoparticles with Different Structural Organization on the Biological Systems of Escherichia coli K12 TGI

E. V. Sorokina and E. A. Obraztsova p. 286  abstract

Biodegradation of Azo Dye Methyl Red by Methanogenic Microbial Communities Isolated from Volga River Sediments

Yu. V. Taktarova, L. I. Shirinkina, A. S. Budennaya, M. A. Gladchenko and I. B. Kotova p. 292  abstract

Cascade Biotransformation of Phytosterol to Testosterone by Mycolicibacterium neoaurum VKM Ас-1815D and Nocardioides simplex VKM Ас-2033D strains

D. N. Tekucheva, V. V. Fokina, V. M. Nikolaeva, A. A. Shutov, M. V. Karpov and M. V. Donova p. 303  abstract

Microbial Community of an 11th Century Manuscript by Both Culture-Dependent and -Independent Approaches

N. Raeisnia, E. Arefian and M. A. Amoozegar p. 313  abstract

Structural and Functional Characterization of Bacterial Biofilms Formed on Phragmites australis (Cav.) in the Rybinsk Reservoir

R. A. Fedorov, I. V. Rybakova, N. L. Belkova and N. A. Lapteva p. 324  abstract

Errata

Erratum to: Pesticide-Degrading and Phosphate-Solubilizing Bacilli Isolated from Agricultural Soil of Punjab (India) Enhance Plant Growth

P. Kumar, A. K. Rai, A. Gupta, H. Phukon, A. Singh, D. Kalita, S. Sharma, K. Harshvardhan and R. C. Dubey p. 336  abstract

Erratum to: New Biocomposite Materials Based on Hydrocarbon-Oxidizing Microorganisms and Their Potential for Oil Products Degradation

Yu. A. Nikolaev, I. A. Borzenkov, E. V. Demkina, N. G. Loiko, T. A. Kanapatskii, I. V. Perminova, A. N. Khreptugova, N. V. Grigor’eva, I. V. Bliznets, N. A. Manucharova, V. V. Sorokin, M. A. Kovalenko and G. I. El’-Registan p. 337  abstract

Erratum to: Deferrivibrio essentukiensis sp. nov., gen. nov., a Representative of Deferrivibrionaceae fam. nov., Isolated from the Subsurface Aquifer of Caucasian Mineral Drinking Waters

D. G. Zavarzina, M. I. Prokofeva, V. A. Pikhtereva, A. A. Klyukina, A. A. Maslov, A. Yu. Merkel and S. N. Gavrilov p. 338  abstract

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[moleculardepot]

Recombinant Arthrobacter globiformis DMGO His

Recombinant Arthrobacter globiformis DMGO His Catalog number: B2017330 Lot number: Batch Dependent Expiration Date: Batch dependent Amount: 100 μg Molecular Weight or Concentration: 92.1kDa (850aa) Supplied as: Solution Applications: a molecular tool for various biochemical applications Storage: −20°C Keywords: N/A Grade: Biotechnology grade. All products are highly pure. All solutions are made…

[instanttimetravelnut]

Urease Market Chain Analysis, Upstream Raw Materials Sourcing and Downstream Buyers by 2024 -Persistence Market Research

Urease is an enzyme in the class of phosphotriesterases and amidohydrolases which catalyzes the hydrolysis reaction of urea thereby forming ammonia and carbon dioxide. The primary source of urease are plants, algae, fungi and yeast. Among the plant sourced, urease jack bean urease are the best characterized and bacteria sourced yield low quantity of urease. Urease has wide industrial applications which includes diagnostic kits for measuring urea, as reducing agent in alcoholic beverages. Besides, urease find major use in the biosensors which are required for hemodialysis systems. Urease inhibitors are also widely used in controlling (slow down) the rate of hydrolysis of urea. Some of the mostly used inhibitors are N-(n-Butyl) thiophosphoric triamide (NBTPT or NBPT) which has less toxicity and ability to get mixed or coated on urea fertilizers. The fertilizers industry and the clinical requirements will boost global urease market during the forecast period.

Get Sample Copy Of This Report @ https://www.persistencemarketresearch.com/samples/12148

Some of the key players identified in the global urease market are BBI Solutions, Sekisui Diagnostics Limited, Sigma-Aldrich Co. LLC., Sisco Research Laboratories Pvt. Ltd etc.

The urease market is primarily driven by its increasing use in the industrial applications such as biosensors. Since plant sourced urease results in less toxicity and almost no side effects further benefits the growth of global urease market. The agronomic and eco-friendly benefits of urease in the inhibitors will fuel the global urease market. Also, the global trend of adoption of organic items over synthetic ones and increasing consumption in clinical diagnostics will aid the growth of global urease market.

The global urease market is segmented on the basis of source and application.

Based on the source, global urease market is segmented into:

Plant Source

Bacterial Source

Fungi Source

Others

Jack Beans

Soy Beans

Lactobacillus ruminis

Corynebacterium lillium

Lactobacillus fermentum

Lactobacillus reuteri

Bacillus fastidiosus

Arthrobacter globiformis

Escherichia coli

Aspergillus niger

Aspergillus nidulans

Rhizopus oryzae

Based on the application, the global urease market is segmented into:

Biosensors

Clinical Chemistry (Diagnostic kits, reducing agent in alcoholic beverages)

Others

Request For TOC @ https://www.persistencemarketresearch.com/toc/12148

The global urease market is geographically divided in to five key regions including North America, Latin America, Europe, Asia-Pacific and Middle East & Africa. North America, especially US holds major share of urease market due the increase consumption in clinical research.  Followed by North America is Europe and Asia Pacific, Latin America and MEA. In Asia Pacific India, Korea, and Bhutan possess major prospectus for urease consumption with majority use as inhibitors for agro industries. The consumption of urease in Latin America is expected to increase during the forecast period with companies such as DASA, the renowned medical diagnostic company in Brazil. The global urease market will show increasing trend of consumption due to industrial applications and clinical diagnostic tests during the forecast period.The research report presents a comprehensive assessment of the market and contains thoughtful insights, facts, historical data, and statistically supported and industry-validated market data. It also contains projections done using a suitable set of assumptions and methodologies. The research report provides analysis and information according to categories such as market segments, geographies, type, machine size and end use.

[annieboltonworld]

Juniper Publishers- Open Access Journal of Environmental Sciences & Natural Resources

Plant Microbiomes and Its Beneficial Multifunctional Plant Growth Promoting Attributes

Authored by Ajar Nath Yadav

Abstract

Plant microbiome (Epiphytic, endophytic and rhizospheric) plays important role in plant growth, development, and soil health. Plant and rhizospheric soil are valuable natural resource harbouring hotspots of microbes, and it plays critical roles in the maintenance of global nutrient balance and ecosystem function. The diverse group of microbes is key components of soil-plant systems, where they are engaged in an intense network of interactions in the rhizosphere/phyllospheric/endophytic. The microbes with plant growth promoting (PGP) attributes have emerged as an important and promising tool for sustainable agriculture. PGP microbes promote plant growth and development directly or indirectly, either by releasing plant growth regulators/phytohormones; solubilization of phosphorus, potassium and zinc; biological nitrogen fixation or by producing siderophore, ammonia, HCN and other secondary metabolites which are antagonistic against pathogenic microbes. The PGP microbes belonged to different phylum of archaea (Euryarchaeota); bacteria (Acidobacteria, Actinobacteria, Bacteroidetes, Deinococcus-Thermus, Firmicutes and Proteobacteria) and fungi (Ascomycota and Basidiomycota), which include different genera namely Achromobacter, Acinetobacter, Agrobacterium, Alcaligenes, Arthrobacter, Aspergillus, Azoarcus, Azospirillum, Azotobacter, Bacillus, Beijerinckia, Brevibacterium, Burkholderia, Collimonas,Curtobacterium, Diplococcus, Enterobacter, Erwinia, Flavobacterium, Flexibacterium, Gluconoacetobacter, Haloarcula, Halobacterium, Halococcus, Haloferax, Herbaspirillum, Klebsiella, Methylobacterium, Microbiospora, Micrococcus, Micromomospora, Nocardioides, PaeniBacillus, Pantoea, Penicillium, Piriformospora, Planomonospora, Pseudomonas, Rhizobium, Serratia, Streptomyces, Thermomonospora and Xanthomonas.These PGP microbes could be used as biofertilizers/bioinoculants at place of chemical fertilizers for sustainable agriculture.

Keywords:     Biodiversity; Endophytic; Epiphytic; Microbiome; Plant Growth Promotion; Rhizospheric; Sustainable Agriculture

Introduction

Plant-microbes interaction is a key for plant growth, development and soil health. An understanding of plant microbiome and their beneficial attributes could have multiple benefits towards sustainable agriculture. Recently, a great emphasis is given on decoding of microbial diversity associated with plants from diverse habitats. Microbial diversity is considered important for maintaining for the sustainability of agriculture production systems. In the 90s, the interaction of microbes with plants was simply thought of as being an effect, but today it is recognized as a process with a high level of complexity in which at least different type of microbes share information without sharing the same spaces from a cellular perspective. In general, there are three kinds of plant-microbes interactions are considered i.e. epiphytic, endophytic and rhizospheric.

The rhizosphere is the zone of soil influenced by roots through the release of substrates that affect microbial activity. It is characterized by greater microbiological activity depending on the distance away from plant roots and constitutes a system especially suitable for obtaining culturable beneficial microbes. The rhizospheric microbes have the ability to attach to the root surfaces allowing these to derive maximum benefit from root exudates. Several factors such as soil type, its moisture, pH and temperature and, age and conditions of plants are known to influence the types of rhizospheric microbes. A number of microbial species belonging to different genera Acinetobacter, Alcaligenes, Arthrobacter, Aspergillus, Azospirillum, Bacillus, Burkholderia, Enterobacter, Erwinia, Flavobacterium, Haloarcula, Halobacterium, Halococcus, Haloferax, Methylobacterium, PaeniBacillus, Penicillium, Piriformospora, Pseudomonas, Rhizobium and Serratia were revealed from rhizosphere of different crop plants [1-8].

The phyllosphere is a common niche for synergism between microbes and plant. The leaf surface has been termed as Phyllosphere and zone of leaves inhabited by microorganisms as phyllo sphere. The plant part, especially leaves are exposed to dust and air currents resulting in the establishments of typical flora on their surface aided by the cuticles, waxes and appendages, which help in the anchorage of microorganisms. The phyllospheric microbes may survive or proliferates on leaves depending on extent of influences of material in leaf diffuseness or exudates. The leaf diffuseness contains the principal nutrients factors (amino acids, glucose, fructose and sucrose), and such specialized habitats may provide niche for nitrogen fixation and secretions of substances capable of promoting the growth of plants. The phyllospheric microbes may performs an effective function in controlling the air borne pathogens inciting plant disease. Microbes on leaf surface are said to be extremophiles as they can tolerate low/high temperature (5-55°C) and UV radiation. Many microbes such as Achromobacter, Agrobacterium, Azotobacter, Bacillus, Beijerinckia, Brevibacterium, Burkholderia, Diplococcus, Flexibacterium, Methylobacterium, Microbiospora, Micrococcus, Micromomospora, Nocardioides, Pantoea, Penicillium, Planomonospora, Pseudomonas, Rhizobium, Streptomyces, Thermomonospora and Xanthomonas have been reported in the phyllosphere of different crop plants [9-15].

The endophytic microbes are referred to those microorganisms, which colonizes in the interior of the plant parts, viz: root, stem or seeds without causing any harmful effect on host plant. The word endophyte means 'in the plant' and is derived of the Greek words end on (within) and python (plant). Endophytic microbes enter in host plants mainly through wounds, naturally occurring as a result of plant growth or through root hairs and at epidermal conjunctions. Endophytes may be transmitted either vertically (directly from parent to offspring) or horizontally (among individuals). A given endophytic microbiome can be modified by factors such as the physicochemical structure of the soil, plant growth phase and plant physiological state, as well as by diverse environmental factors [16,17].

The main colonization route used by endophytes seems to be the rhizosphere. Microbes reach the rhizosphere by chemotaxis towards root exudates components followed by attachment. The lipopolysaccharide and exopolysaccharide are bacterial components shown to play roles in attachment of endophytes to plant tissue. The preferred site of attachment and subsequent entry is the apical root zone with a thin-walled surface root layer, such as the cell elongation zone and the root hair zone with small cracks caused by the emergence of lateral roots. Root regions such as the differentiation zone and intercellular spaces in the epidermis have been suggested to be preferential sites for microbial colonization as well. Root cracks, wounds caused, for instance, by arthropods or nematodes, and emergence sites of lateral roots are generally considered as the main 'doors' for microbial penetration. Bacterial traits putatively involved in endophytic colonization of plant roots. For penetration, the bacteria have to produce cellulolytic enzymes required to hydrolyse the exothermal walls, such as endoglucanases and endopolygalacturonidases [18]. These enzymes also seem to be important for spreading through the intercellular space of the root cortex and beyond. Endophytes usually do not enter plant cells. Only a few of them can penetrate the endow dermal barrier and invade the xylem vessels. Endophytic microbes live in plant tissues without causing substantive harm to the host. Endophytic microbes exist within the living tissues of most plant species in form of symbiotic to slightly pathogenic. A large number of endophytic microbial species Achromobacter, Azoarcus, Burkholderia, Collimonas, Curtobacterium, Enterobacter, Flavobacterium, Gluconoacetobacter, Herbaspirillum, Klebsiella, Microbiospora, Micromomospora,Nocardioides, Pantoea, Planomonospora, Pseudomonas, Serratia, Streptomyces and Thermomonospora have been identified from different host plants [6,8,10,15,18-21].

The study on microbial biodiversity of plant associated microbes revealed representative microbes from archaea (Euryarchaeota); bacteria (Acidobacteria, Actinobacteria, Bacteroidetes, Deinococcus-Thermus, Firmicutes and Proteobacteria) and fungi (Ascomycota and Basidiomycota). Literature review suggested that the distribution of microbes although varied in all bacterial phyla, but Proteobacteria were most dominant and ubiquitous followed by Actinobacteria. Among different classes of Proteobacteria i.e. α, β, γ and δ-proteobacteria, the members of γ-proteobacteria were most dominant and have been reported from different crop plants. Least number of microbes was reported from phylum Deinococcus-Thermus and Acid bacteria followed by Bacteroidetes [18,22-26] (Figure 1). There are very few reports of archaea as PGP including rhizospheric as well as endophytic [27-29].

Actinobacteria is a phylum of gram-positive bacteria and divided into five classes' viz. Acidimicrobiia, Actinobacteria, Coriobacteriia, Nitriliruptoria, Rubrobacteria and Thermoleophilia. Members of class Actinobacteria are most dominant and found to associate with plants growing in different habitats as well as extreme environments. It also contains one of the largest of bacterial genera, Streptomyces [30-32]. The rhizospheric Actinobacteria are most dominant in nature and they are of great economic importance to humans because agriculture and forests depend on their contributions to soil systems. Among different groups of microbes, the member Bacillus and Bacillus derived genera are belonged to phylum Firmicutes, which most culturable and colonize with different plants such as wheat, rice, maize, soybean, and chickpea [33-37]. The phylum Firmicutes, have been further distributed into five families, Bacillaceae, Bacillales Incertae Sedis, PaneniBacillaceae, Planococcaceae and Staphylococcaceae and reported from most of crop plants studies [6-8,10,12,15]. Among different phylum the Proteobacteria one of the predominant phylum including many dominant genera including Brevundimonas terrae, Bosea sp. and Methylobacterium sp. from α-proteobacteria; Burkholderia sp, Burkholderia cepacia, Variovoraxginsengisoli,Janthinobacterium lividum and Janthinobacterium sp. from β-proteobacteria and Aeromonas, Pantoea, Providencia, Pseudomonas, Psychrobacter and Yersinia from γ-proteobacteria class [6-8,18,38].

*P-Phosphorus; NF-Nitrogen fixation; IAA- Indole acetic acids; Sidero- Siderophores; ACC-1-aminocyclopropane-1-carboxylate (ACC) deaminase

Plant associated microbes have been shown be beneficial by promoting plant growth either directly, e.g. by fixation of atmospheric nitrogen, solubilization of minerals such as phosphorus, potassium and zinc; production of Sidero pores and plant growth hormones such cytokinins, auxins and gibberellins or indirectly, via production of antagonistic substances by inducing resistance against plant pathogens [3,38-41]. Biological nitrogen fixation (BNF) is one of the possible biological alternatives to N-fertilizers and could lead to more productive and sustainable agriculture without harming the environment. Many associative microbes are now known to fix atmospheric nitrogen and supply it to the associated host plants. A variety of nitrogen fixing microbes like Arthrobacter, Azoarcus, Azospirillum, Azotobacter, Bacillus, Enterobacter, Gluconoacetobacter, Herbaspirillum, Klebsiella, Pseudomonas, and Serratia have been isolated from the rhizosphere of various crops, which contribute fixed nitrogen to the associated plants [18,42-44] (Figure 2) (Table 1).

Plant-associated microbes typically produce plant growth hormones such as auxins and gibberellins. The gibberellins production is most typical for the root-associated microbes and auxins production is common to all plant-associated microbes. Auxins can promote the growth of roots and stems quickly (by increasing cell elongation) or slowly (through cell division and differentiation). The production of such growth regulators by microbes provides numerous benefits to the host plant including the facilitation of root system expansion, which enhances the absorption of water and nutrients and improves plant survival. The ability to synthesize these phytohormones is widely distributed among plant-associated microbes [45-47]. Diverse microbial species possess the ability to produce the auxins phytohormone indole acetic acid (IAA). Reviewing the role of bacterial IAA in different microorganism-plant interactions highlights the fact that microbes use this phytohormone to interact with plants as part of their colonization strategy, including phyto-stimulation and circumvention of basal plant defense mechanisms. The IAA application has also been suggested to promote plant growth or suppress weed growth.

Phosphorus (P) is major essential macronutrient for biological growth and development. Microbes offer a biological rescue system capable of solubilizing the insoluble inorganic P of soil and make it available to the plants. The ability of some microbes to convert insoluble P to an accessible form, like orthophosphate, is an important trait in PGP microbes for increasing plant yields. The rhizospheric P-utilizing microbes could be a promising source for plant growth promoting agent in agriculture. P-solubilization is a common trait among microbes associated with different crops. For instance, the majority of microbial populations from wheat, rice, maize, and legumes were able to solubilise mineral phosphates, and a vast number of PGP microbes with P solubilizing property have been reported which include members belonging to Burkholderia, Enterobacter, Halolamina, Pantoea, Pseudomonas, Citrobacter and Azotobacter [48-54] (Table 1). Possible mechanisms for solubilization from organic bound P involve either enzymes namely C-P lyase, nonspecific phosphatases and phytases [55,56]. However, most of the bacterial genera solubilize P through the production of organic acids such as gluconate, ketogluconate, acetate, lactate, oxalate, tartarate, succinate, citrate and glycolate. Type of organic acid produced for P solubilization may depend upon the carbon source utilized as substrate. Highest P solubilization has been observed when glucose, sucrose or galactose has been used as sole carbon source in the medium [27,57].

Ethylene is a stress-induced plant hormone that can inhibit plant growth. Some microbes can lower the level of ethylene in the plant by cleaving the plant-produced ethylene precursor 1-aminocyclopropane-1-carboxylate (ACC). Inoculation of such microbes can mitigate the effect of various stressors by sustaining plant growth in the face of ethylene. ACC-deaminase producing microbes may play a role in regulating ethylene levels after such bursts, ensuring that ethylene levels stay below the point where growth is impaired. Ethylene is a key regulator of the colonization of plant tissue by bacteria which in turn suggests that the ethylene inhibiting effects of ACC- deaminase may be a microbial colonization strategy. Generally, ethylene is an essential metabolite for the normal growth and development of plants [58-61]. This plant growth hormone is produced endogenously by approximately all plants and is also produced by different biotic and abiotic processes in soils and is important in inducing multifarious physiological changes in plants. Apart from being a plant growth regulator, ethylene has also been established as a stress hormone. Under stress conditions like those generated by salinity, drought, water logging, heavy metals and pathogenicity, the endogenous level of ethylene is significantly increased which negatively affects the overall plant growth. PGP microbes which possess the enzyme, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, facilitate plant growth and development by decreasing ethylene levels, inducing salt tolerance and reducing drought stress in plants. Microbial strains exhibiting ACC deaminase activity have been identified in a wide range of genera such as Acinetobacter, Achromobacter, Agrobacterium, Alcaligenes, Azospirillum, Bacillus, Burkholderia, Enterobacter, Pseudomonas, Ralstonia, Serratia and Rhizobium [6,8,61-65] (Figure 2)(Table 1).

The indirect mechanism of plant growth occurs when microbes lessen or prevent the detrimental effects of pathogens on plants by production of inhibitory substances or by increasing the natural resistance of the host [66-72]. Phytopathogenic microbes can control by releasing siderophore, chitinases, antibiotics, fluorescent pigment or by cyanide production [73,74]. Biocontrol systems are eco-friendly, cost-efficient and involved in improving the soil consistency and maintenance of natural soil flora [75-77]. To act efficiently, the Biocontrol agent should remain active under large range of conditions viz., varying pH, temperature and concentrations of different ions. Biocontrol agents limit growth of pathogen as well as few nematodes and insects. Biocontrol microbes can limit pathogens directly by producing antagonistic substances, competition for iron, detoxification or degradation of virulence factors; or indirectly by Inducing Systemic Resistance (ISR) in plants against certain diseases, signal interference, competition for nutrients and niches and interference with activity, survival, germination and speculation of the pathogen. Iron is a necessary cofactor for many enzymatic reactions and is an essential nutrient for virtually all organisms. In aerobic conditions, iron exists predominantly in its ferric state (Fe3+) and reacts to form highly insoluble hydroxides and ox hydroxides that are largely unavailable to plants and microorganisms. To acquire sufficient iron, siderophore produced by bacteria can bind Fe3+ with a high affinity to solubilizing this metal for its efficient uptake.

Bacterial siderophores are low-molecular-weight compounds with high Fe3+ chelating affinities responsible for the solubilization and transport of this element into bacterial cells. Some bacteria produce hydroxamate-type siderophores, and others produce catecholate-types [78,79]. In a state of iron limitation, the siderophore-producing microorganisms are also able to bind and transport the iron-siderophore complex by the expression of specific proteins. The production of siderophores by microorganisms is beneficial to plants because it can inhibit the growth of plant pathogens. siderophores have been implicated for both direct and indirect enhancement of plant growth by plant growth promoting microbes.

Conclusion and Future Prospect

The microbes are capable of colonizing the rhizosphere, phyllosphere as well as living inside the plant tissues as endophytes. Biotechnology has opened up new possibilities concerning the application of these microbes for the beneficial applications in soil for the promotion of plant growth and the biological control of soil-borne pathogens. The nutritional and environmental requirements of these microbes are very diverse. Due to the diverse range of activities as well as the number of microbes in varying habitats around the world, these are important bioresources towards rationalized use of chemicals fertilizers in agriculture. An understanding of plant microbiome for major crops will be of significant importance for exploring efficient use of these microbes.

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[juniperpublishers-agriculture]

In vitro Screening and Identification of P-Solubilizing Rhizobacteria Associated with Sorghum bicolor L.

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Abstract

In the present study, P-solubilizing rhizobacteria were screened and identified from Sorghum bicolor L root adhering soil and root which were collected from sorghum growing zones of Tigray, Ethiopia. A total of 94 bacteria were isolated from root washing solutions and surface sterilized roots. These isolates were evaluated for their ability to solubilize phosphates on Pikovskaya’s agar plates. The P-solubilizing bacterial isolates were identified by GEN III Biolog bacterial identification system. Fifty four of the 94 (57.5%) rhizobacterial isolates showed clearly visible haloes (>0.50cm) around their colonies on Pikovskaya’s agar after seven days of incubation. The solubilization index (SI) of the potential P-solubilizing rhizobacterial isolates differed significantly (p<0.05) and ranged from 0.5 to 4.83. Gram negative rhizobacteria dominated the identified P-solubilizing Rhizobacteria isolates and produced larger solubilization indices when compared with the Gram-positive isolates. Members of the phosphobacteria were dominated by the genus Pseudomonas (35.71%). Some of the isolates lost their capacity for phosphate solubilization on repeated sub-culturing. Overall, this finding indicated that there is a great number of rhizobacterial potential associated with Sorghum bicolor L which can be utilized for development of P-solubilizing bio-fertilizers.

Keywords: P-solubilizing rhizobacteria; Sorghum bicolor L.; Biolog bacterial identification

Abbreviations: PGPR: Plant Growth Promoting Rhizobacteria; PSM: Phosphate Solubilizing Microbes; PSB: Phosphate Solubilizing Bacteria; CD: Colony Diameter; SI: Solubilization Index; BUG: Biolog Universal Growth

    Introduction

Plant growth promoting rhizobacteria (PGPR) flourish in the rhizosphere of plant, which may grow in, on, or around plant tissues and exert beneficial effects on plant development [1,2]. They possess the capacity to stimulate plant growth either directly or indirectly [3]. PGPR can affect plant growth by a wide range of mechanisms such as solubilization of inorganic phosphate, production of phyto-hormones, siderophores and organic acids, lowering of plant ethylene levels, N2 fixation and bio-control of plant diseases [4,5]. The use of such beneficial bacteria as bio-fertilisers and bio-control agents has currently attracted increased interest world-wide in attempts to achieve sustainability, particularly in agriculture, forestry and horticulture [5].

The number of PGPR that have been identified has seen a great increase in the last few years, mainly because of the role of the rhizosphere as an ecosystem has gained importance in the functioning of the biosphere. Various species of bacteria like Pseudomonas, Azospirillum, Azotobacter, Klebsiella, Enterobacter, Alcaligenes, Arthrobacter, Burkholderia, Bacillus and Serratia have been reported to enhance plant growth. There are several PGPR inoculants currently commercialized that seem to promote growth through at least one mechanism; suppression of plant disease (termed Bio-protectants), improved nutrient acquisition (Bio-fertilizers), or phyto-hormone production (Bio-stimulants) [2].

The use of PGPR offers an attractive way to replace chemical fertilizer, pesticides, and supplements; most of the isolates result in a significant increase in plant height, root length, and dry matter production of shoot and root of plants. The economic and ecological problems of today have re-invigorated the idea of using bio-fertilizers and bio-control agents in order to reduce the application of costly and environmentally-polluting agrochemicals to a minimum [6,7]. Agrochemicals (namely fertilizers and pesticides) have greatly influenced natural rhizosphere microbes in agro-systems [8]. Plant beneficial microbial bio-resources promise to replace or supplement many such destructive, high intensity practices and support ecofriendly crop production [6,7]. In particular, plant growth promoting rhizobacteria (PGPR) for the benefits of agriculture and ecosystem functions is gaining worldwide importance and acceptance [6,7,9,10].

Phosphorus is the second most important nutrient for plants, after nitrogen. It exists in soil as mineral salts or incorporated into organic compounds. Despite these phosphorus compounds being abundant in agricultural soils, the majority of them occur in an insoluble form. Plants require approximately 30μmol l-1 of phosphorus for maximum productivity, but only about 1μmol l-1 is available in many soils. Therefore, the unavailability of phosphorus in many soils has been recognized as a major growth limiting factor in agricultural and horticultural systems. This necessitates the application of soluble forms of phosphorus in the form of phosphate fertilizers, which in itself has constraints in that it too is rapidly immobilized (fixed) to insoluble forms upon its application in the soil due to its reaction with aluminum and iron minerals. The efficiency of applied phosphorus rarely exceeds 30% due to fixation in soil. It is also lost as a result of run-off and leaching, leaving as little as 10-20% available for plant utilization. Phosphate fertilizers are dependent on phosphorus derived from phosphate rock, which is a non-renewable resource and current global reserves may be depleted in 50-100 years. Therefore, exploring alternative forms of agriculture, where nutrient conservation is key, is of vital importance [11].

Several reports have indicated that different bacterial species, particularly rhizosphere colonizing bacteria, have the ability to liberate organic phosphates or to solubilize insoluble inorganic phosphate compounds such as tri-calcium phosphate, di-calcium phosphate, hydroxyapatite, and rock phosphate. These bacteria make available the soluble phosphates to the plants, and in return gain root borne carbon compounds, mainly sugars and organic acids, necessary for bacterial growth [12]. Current research suggests that the inoculation of crops with Phosphate Solubilizing Microbes (PSM) has the potential to reduce application rates of phosphate fertilizer by 50% without significantly reducing crop yield [13,14]. Phosphate Solubilizing Bacteria (PSB) may also be useful in the phyto-remediation of heavy metal impacted soil [15,16] or for bioleaching of rare Earth elements for mined ores [17].

Most soils in tropical and subtropical areas are predominantly acidic and extremely P-deficient due to their strong fixation of P as insoluble phosphates of iron and aluminum [9,12,18]. This leads to wide P deficiency which is particularly the case for the large parts of Ethiopian soils [19,20]. To alleviate P deficiency, chemical phosphate fertilizers are widely used. However, a large proportion of the soluble forms of P fertilizers is precipitated in insoluble form soon after application and becomes unavailable to plants [21]. This in turn leads to a need for excessive and repeated application of soluble P fertilizers, which in addition to the economic constraint can pose a serious threat to groundwater. These have been the major stresses that constrain the production of crops in the country.

Thus, in relation to this fact, P-solubilizing Rhizobacteria associated with cultivated Sorghum plant roots that displayed bio-fertilizer characteristics and have potential applications as native P-solubilizing bacterial bio-fertilizers were screened and identified in this study.

    Materials and Methods

Description of sample collection areas

Sample collection was carried out in two major sorghum producing zones of Tigray region in Ethiopia. The sample collection site is shown in Figure 1. It comprises Central Tigray and South Tigray zones which are found in the northern part of Ethiopia. Based on the GPS data recorded during sample collection, the sample collection sites are located between 12O28.0988’- 13O19.9522’N and 38O53.1815’- 39O40.9870’E with an altitude range of 1342-1822m a.s.l.

Sample collection

A total of 93 sorghum roots with adhering soil samples were collected in sterile plastic bags. Samples were collected based on altitude differences of sorghum plant growing areas, cultivar types and plant age group. At each sampling site, plant roots with adhering soil (approximately 50g) were uprooted and placed into a sterile plastic bag. Care was taken to keep rhizosphere soil intact around the root. The collected samples were kept in ice-box and transported to Ethiopian Biodiversity Institute Microbiology Laboratory. All samples were kept at 4 ˚C until use [22-24].

Isolation of Rhizobacteria

Sorghum roots with adhering soils were merged into 17 composite samples separately based on similarity of cultivar type, plant and age group. The root adhering soils were dislodged from the roots using sterile distilled water by shaking at 250rpm for 20 minute and the root washing solutions were used for the isolation of rhizoplane bacteria [25]. For the isolation of bacterial endophytes, merged and washed roots were surface sterilized in 99% ethanol for 1min, 3% NaOCl for 6 minutes, and 99% ethanol for 30 seconds and followed by rinsing with sterile distilled water for 6 times [23]. Before homogenization, a root fragment was imprinted on nutrient agar to serve as a sterility check. Roots were homogenized and macerated with a sterile mortar and pestle [26]. The root washing solutions and homogenized roots were serially diluted (10-2 to 10-4) aseptically for inoculation. 0.1ml inoculums of the prepared samples were spread onto Nutrient agar plates and incubated at 30+2 ˚C for 48h [27,28]. Bacterial colonies with distinct and peculiar morphologies were selected and re-streaked to obtain pure colonies [24].

In vitro screening of bacteria for P-solubilization potential

Phosphate solubilization ability of the isolated bacteria was determined on Pikovskaya’s agar. The isolates were spotted onto Pikovskaya’s agar and incubated for 7 days at 30 ± 2 ˚C. The presence of halo zone around the bacterial colony was considered as indicator for positive phosphate solubilization. Further, the solubilization index (SI) of the isolates was determined by measuring the halo zone of clearance (HD) in the Pikovskaya’s agar plates and the colony diameter (CD) [29]. SI was calculated with the formula: SI = (CD+HD)/CD. Three replicate plates were used for each isolate [30].

Identification of P-solubilizing rhizobacteria

Preliminary identification of P-solubilizing Rhizobacteria isolates were performed by examination for cell morphology using optical microscopy, Gram staining, and colony morphology [27,24]. Biochemical identification including the carbohydrate fermentation patterns and chemical sensitivity tests were determined using GEN III Biolog bacterial identification system kit. The Biolog GEN III Micro Plate analyzes a microorganism in 94 phenotypic tests: 71 carbon source utilization assays and 23 chemical sensitivity assays. The test panel provides a “Phenotypic Finger print” of the microorganism that can be used to identify it at the species level. The plates contained 96 wells, with a dehydrated panel of necessary nutrient medium (a carbon source), biochemical and tetrazolium violet. Tetrazolium violet is a purple formazan, a redox dye that turns purple when reduced, indicating use of the carbon source provided or resistance to inhibitory chemicals. Each plate contained a positive and negative control well. Pure culture of bacteria isolates was grown on Biolog BUG agar plates at 30 ± 2 ˚C for 20-24 hours. Single colonies were swabbed and suspended in inoculating fluid A. Cell suspensions (100μl) adjusted at 90-98% transmittance was pipetted into 96 well Biolog Micro-plates for carbon utilization and chemical test. Panels were incubated at 30 ± 2 ˚C for 20-24 hours. The microplates were inserted into the Omnilog automatic system and the identification process was carried out using GEN III Biolog- Omnilog identification system software [31].

Data analysis

Data were analyzed using SPSS software version 20 (SPSS Inc., Chicago, IL, USA). Coefficient of variation was calculated for the significances of differences within samples and ANOVA was employed for significances of differences between mean counts of microbial groups. DIVA_GIS 7.5.0 was used for mapping study areas.

    Results and Discussion

In vitro screening of P-solubilizing rhizobacteria

Ninety-four bacteria were isolated from root washing solutions and surface sterilized roots on nutrient agar. Fifty-one bacteria were isolated from sorghum root washing solutions which were prepared from the root adhering soils and the rest 43 were endophyte bacteria isolated from sorghum roots. These 94 bacterial isolates were evaluated for their ability to solubilize phosphates on Pikovskaya’s agar plates (Table 1). Fifty four of the 94 (57.5%) rhizobacterial isolates showed clearly visible haloes (>0.50cm) around their colonies on Pikovskaya’s agar after seven days of incubation. The solubilization index (SI) of the potential P-solubilising rhizobacterial isolates differed significantly (p<0.05) and ranged from 0.5 to 4.83. Bacterial strain TS RWS7b produced the largest zone of solubilisation, followed by TS RWS 1b.

Identification of P-solubilizing rhizobacteria

Based on colony morphology shown on nutrient agar and Biolog Universal Growth (BUG) agar, and Gram staining similarity, the 54 P-solubilizing Rhizobacteria screened from root washing solutions and sorghum roots were clustered into 17 representative isolate morphological groups. Inoculums of the 17 clustered representative isolates were prepared and transferred into GEN III Micro-plates. After 24 hours of incubation at 30+2 ˚C, the microplates were subjected to Biolog-Omnilog bacterial identification system test. Fourteen of the 17 clustered representative P-solubilizing Rhizobacteria isolates were identified (Table 1).

Eleven of the 14 identified P-solubilizing Rhizobacteria were isolated from root washing solution and the rest 3 were isolated from sorghum root. Gram negative rhizobacteria dominated the system accounting for 78.57% (11/14) of the identified P-solubilizing Rhizobacteria isolates (Table 1,2). Previous observation showed that the rhizosphere of many agriculturally important plants favors more Gram negative rhizobacteria than the Gram positives [4,32]. The largest solubilization index was also produced by Gram negative isolate when compared with Gram-positive isolate. Some of the isolates lost their capacity for phosphate solubilization on repeated sub-culturing as previously reported in many other studies [33,34].

Ten different genera of Rhizobacteria were identified. Most of them were isolated from root washing solutions. Eight of the 10 identified Rhizobacteria genera were isolated only from sorghum root washing solutions. But, only Stenotrophomonas species was isolated from root. Meanwhile, Pseudomonas species was isolated from both root washing solutions and root. Members of the phosphobacteria were dominated by the genus Pseudomonas (35.71%) (Table 2). Pseudomonas are the most dominant genera commonly reported in many plant studies [35].

Conclusion

This study showed that there are a large proportion of P-solubilizing rhizoplane and endophytes rhizobacteria associated with Sorghum bicolor L. Pseudomonas is the most dominant rhizobacteria both in the root adhering soil and roots of sorghum. In general, Gram negative bacteria were not only more predominant than Gram positive bacteria but also, they produced the largest solubilization index. This finding indicated that there is a great number of rhizobacterial potential associated with Sorghum bicolor L. which can be utilized for development of P-solubilizing bio-fertilizers.

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[juniperpublishersmicrobiology]

Extreme Cold Environments: A Suitable Niche for Selection of Novel Psychrotrophic Microbes for Biotechnological Applications

Authored by  Ajar Nath Yadav

Editorial

The microbiomes of cold environments are of particular importance in global ecology since the majority of terrestrial and aquatic ecosystems of our planet are permanently or seasonally submitted to cold temperatures. Earth is primarily a cold, marine planet with 90% of the ocean's waters being at 5°C or lower. Permafrost soils, glaciers, polar sea ice, and snow cover make up 20% of the Earth's surface environments. Microbial communities under cold habitats have been undergone the physiological adaptations to low temperature and chemical stress. Recently, these communities have attained the focus of applied research not only in terms of biotechnological prospects but also to understand the use of primitive analogues of biomolecules existed during early Earth environments [1,2]. The microbiomes of cold environments have been extensively investigated in the past few years with a focus on culture dependent and culture-independent techniques. Cold-adapted microorganisms have been reported from Antarctic sub-glacial, permanently ice-covered lakes, cloud droplets, ice cap cores from considerable depth, snow and ice glaciers [3-6]. Many novel microbes have been sort out from cold environments including Halobacterium lacusprofundi [7], Sphingobacterium antarcticus [8], Octadecabacter arcticus [9], Hymenobacter roseosalivarius [10], Cellulophaga algicola [11], Flavobacterium frigidarium [12], Oleispira antarctica [13], Flavobacterium psychrolimnae [14], Psychromonas ingrahamii [15], Exiguobacterium soli [16], Pseudomonas extremaustralis [17], Cryobacterium roopkundense [18], Sphingomonas glacialis [19], Pedobacter arcticus [20], Sphingobacterium psychroaquaticum [21], Lacinutrix jangbogonensis [22], Massilia eurypsychrophila [23], Glaciimonas frigoris [24] and Psychrobacter pocilloporae [25]. There are several reports on whole genome sequences of novel and potential psychrotrophic microbes [26,27].

The novel species of psychrotrophic microbes have been isolated worldwide and reported from different domain archaea, bacteria and fungi which included members of phylum Actinobacteria, Proteobacteria, Bacteroidetes, Basidiomycota, Firmicutes and Euryarchaeota [7-25]. Along with novel species of psychrotrophic microbes, some microbial species including Arthrobacter nicotianae, Brevundimonas terrae, Paenibacillus tylopili and Pseudomonas cedrina have been reported first time from cold deserts of NW Himalayas and exhibited multifunctional plant growth promoting (PGP) attributes at low temperatures [5]. In a study by Yadav et al. [6], the microbial species Alishewanella sp., Aurantimonas altamirensis, Bacillus baekryungensis, B. marisflavi, Desemzia incerta, Paenibacillus xylanexedens, Pontibacillus sp., Providencia sp., P. frederiksbergensis, Sinobaca beijingensis and Vibrio metschnikovii have been reported first time from high altitude and low temperature environments of Indian Himalayas. Wheat associated psychrotrophic bacteria Arthrobacter methylotrophus and Pseudomonas rhodesiae have been reported first time from wheat growing in North hills zone of India [28]. In a specific search of economically important Bacillus and Bacillus derived genera (BBDG) at low temperature, Various BBDG such as Bacillus psychrosaccharolyticus, B. amyloliquefaciens, B. altitudinis, B. Muralis, Paenibacillus tylopili, P. pabuli, P. terrae and P lautus with efficient PGP attributes have been reported first time by Yadav et al. [29].

Prospecting the cold habitats has led to the isolation of a great diversity of psychrotrophic microbiomes. The bacterialAdv Biotech & Micro 2(2): AIBM.MS.ID.555584 (2017)diversity from the cold environment could serve as a database for selection of bio-inoculants with PGP ability and could be used for improving the growth and yield of crops grown at high altitudes with prevailing low temperatures [30-33]. Psychrotrophic PGP microbes have been shown to promote plant growth either directly by biological N2-fixation; solubilization of minerals such as phosphorus, potassium and zinc; production of siderophores and plant growth hormones (Indole acetic acid and gibberellic acid) or indirectly, via production of antagonistic substances by inducing resistance against plant pathogens [29,34,35]. The psychrotrophic PGP microbes can have an impact on plant growth providing the plant with compound(s) of microbial origin for facilitating the uptake of nutrients from the environment. Psychrotrophic PGP microbes were found in several genera, including Arthrobacter, Bacillus, Brevundimonas Burkholderia, Pseudomonas, Citricoccus, Exiguobacterium, Flavobacterium, Janthinobacterium, Kocuria, Lysinibacillus, Methylobacterium, Microbacterium, Paenibacillus, Providencia and Serratia [3538]. Among these taxa, Pseudomonas and Exiguobacterium has been the best characterized for PGP at low temperatures [38,39]. There are several studies have demonstrated the benefits of PGP microbes on the growth and yield of different crops at different climates, soils, and temperatures. The use of PGP microbes improves plant growth by supplying plant nutrients, which can help sustain environmental health and soil productivity.

Psychrophilic/psychrotolerant microbes are important for many reasons, particularly because they produce cold- active enzymes. The enzymes from psychrophiles have become interesting for industrial applications, partly because of ongoing efforts to decrease energy consumption. These cold-active enzymes provide opportunities to study the adaptation of life to low temperature and the potential for biotechnological exploitation [2,40]. Most of the work that has been conducted on psychrophilic bacteria focused on cold-active enzymes such as amylase, protease, lipase, pectinase, xylanase, cellulase, P-glucosidase, p-galactosidase and chitinase [40]. Cold- active enzymes are produced by psychrophilic microbes namely, Acinetobacter, Aquaspirillium, Arthrobacter, Bacillus, Carnobacterium, Clostridium, Cytophaga, Flavobacterium, Marinomonas, Moraxella, Moritella, Paenibacillus, Planococcus, Pseudoalteromonas, Pseudomonas, Psychrobacter, Shewanella, Vibrio and Xanthomonas [27,41,42]. Psychrophilic microbes can be applied for biodegradation of agro wastes at low temperatures. Shukla et al. [43], have developed psychrotrophic microbial consortium of Eupenicillium crustaceum, Paceliomyces sp., Bacillus atropheus and Bacillus sp., for its potential applications towards degradation of agri-residues and conversion to a value added product like compost for enhancing soil fertility and decreasing environmental pollution caused by burning of agro-wastes. Psychrotrophic microbes produced anti-freezing compounds (AFCs) at low temperatures [1,27]. The AFCs are useful in cryosurgery and also in the cryopreservation of isolated organs, cell lines, tissues and whole organisms. In food industry, anti-freezing proteins (AFPs) can be used to improve the quality of frozen food. Improved cold tolerance in fishes has been achieved in some cases by direct injection of AFPs and in another case by transgenic expression of an AFPs.

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Conclusion

Cold-adapted microbes could be utilized for understanding adaptation at low temperatures, as they produce cold-active enzymes, fatty acids, carotenoids, cold acclimation proteins, cryoprotectants and anti-freezing proteins under extreme conditions of low temperature. Cold-active enzymes have applications in industry like those manufacturing cleaning agents or in leather processing. The other applications could be for bio-degradation of xenobiotic compounds in cold climes, food processing (bakery, cheese manufacture and fermentation) and molecular biology (heterologous gene expression). Cold- adapted microbes have attracted the attention of the scientific community due to their ability to promote plant growth and produce cold-active enzymes, with potential biotechnological applications in a broad range of industrial, agricultural and medical processes. Psychrotrophic microbes could be valuable in agriculture as bio-inoculants and biocontrol agents for low temperature habitats. The use of psychrophiles as biofertilizers, biocontrol agent and bioremediators would be of great use in agriculture under cold climatic conditions.

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