microcomixblog-blog

[microcomixblog-blog]

for more microbial fun, please visit MicroComix: a collaborative webcomic by a wife/wife team of STEM nerds.

So tinyB and I were hanging out at home yesterday when it came to our attention that tinyB did not actually know what a gene is. Which is totally okay! (But also kind of surprising because I only talk about genes like all. the. time. Hey, I mean, I hear people talking about sports all the time and I never know what being “offside” really means, so. No judgement.)

In biology, there’s this thing about the central dogma. There’s a Wikipedia article about it! I’ll be the first to admit that the first time I heard it being called the central dogma, I thought it sounded cult-ish. And like to be perfectly honest, the central dogma is kind of important on a God-like level to biologists. Basically, the story goes like this:

DNA -> RNA -> protein

That’s all there is to it!

Buuuuuut as with most things in nature, reality is a little more complicated than that. Let’s go back to What Is Gene 101, though.

So you know how you have DNA, right? That stuff that encodes what color eyes you have, how many fingers you have, whether you’re tall or short, hairy or smooth. (Personally, I blame my genes ~888 times a day for giving me 20000x hair. But.)

That DNA is like a long string made up of only four different types of “blocks”: A, T, C, and G. This string is made up of two different strands, and they pair up so that A goes with T on the opposite strand, and C goes with G on the opposite strand.

This DNA then becomes RNA, which is like DNA except instead of being double-stranded, it is single-stranded, and the “T” blocks in DNA are “U” blocks. The process by which DNA becomes RNA is called transcription. After that, RNA becomes protein through a process called translation. I’ve also recently become aware that while most people kinda sorta know what DNA and protein is (btw while meat is composed of proteins, so are a lot of other things, so when I start talking about bacteria making proteins, I’m not talking about teeny tiny butcheries), a lot of people don’t really understand RNA as well. And I don’t mean that just among regular people, I think this is true in the science community as well, which is a huge pity because a lot is being controlled at the RNA level.

But that’s a huge topic for another day.

Let’s go back to the hero of today: genes. A “gene” is just a stretch of DNA that eventually leads to making a protein. Not all parts of your DNA encode for a protein! Bacteria genomes are VERY densely packed compared to that of eukaryotes (e.g. humans). In fact, they arrange their genes into “operons,” which is a set of genes that often perform related functions.

For example, if you want to make stew, it does you no good to just cut the vegetables. You got to take out a pot, fill it with water, turn on the heat, boil the water, cut the vegetables, throw in the vegetables, wait, turn off the heat, and put the stew in a bowl. It makes sense in your brain that those actions come as a set in the same way that it makes sense for the bacteria to organize their genes in a set so that they make the necessary genes for a certain task all at once.

In humans, the genes aren’t packed as densely in our genome. In fact, we used to think that there was just a lot of “garbage” DNA sitting around between the useful portions (i.e. the genes) that didn’t serve any purpose; nowadays, though, we know that those portions which don’t make proteins can serve essential regulatory functions. Some of that DNA doesn’t make a protein, but instead stops at the RNA stage, and that RNA can bind to DNA or proteins to activate or deactivate it.

So what does it mean when Mom tells Callie to “put on” her genes if she’s cold? Well, it turns out that even if you have a gene, it doesn’t mean that that gene is currently being made into protein. This is become not all genes are transcribed(remember? DNA -> RNA). There are “housekeeping��� genes which the cell needs constantly for all its processes to run smoothly. These are usually expressed all the time. But there are a lot of genes that the cell doesn’t need that would only be a waste of energy to make into protein. Generally, the cell receives an external signal which reaches the promoter of that gene, stimulating transcription of that gene.

Therefore, you can put two bacteria with the exact same genes in different environments, and they can behave and look very different!

[microcomixblog-blog]

for more microbial fun, please visit MicroComix: a collaborative webcomic by a wife/wife team of STEM nerds.

So when people talk about bacteria, most of the time they’re talking about the ones that make you sick. But did you know that bacteria get sick too??

Yeah, there’s these things called bacteriophage, which are like viruses that infect bacteria! They work more or less the way as viruses which infect humans, by injecting their own DNA into that of the host and borrowing the host’s replication machinery to build more of themselves. It’s like forcefully breaking into someone’s house with a rockin’ pizza recipe and making thousands of pizzas with their kitchen and food…and eventually, driving a truck through their back door with your 102k pizzas in tow.

It’s kind of rude.

Also note that this month’s comic features Phil the Streptococcus thermophilus, an important bacteria for making yogurt! My lovely wife, who did the character design and story board, and I chose this bug for the bacteriophage comic because of its significance in the discovery of CRISPR. CRISPR/Cas9 earned its claim to fame in the popular media after it was developed as for genomic editing in eukaryotes, but actually, the people originally doing research on it wanted to know how it served as an adaptive immune system for bacteria.

So you know how if you get the chicken pox once, you won’t get it again? Turns out that bacteria also have a system where if they get infected by one type of bacteriophage, they’ll store a short sequence from that phage in the CRISPR section of its genome so that if that same phage tries to infect again, the bacteria will be immune!

For a tiny little mix-bag of molecules, that’s pretty solid.

[microcomixblog-blog]

for more microbial fun, please visit MicroComix: a collaborative webcomic by a wife/wife team of STEM nerds.

this is caulobacter crescentus. it is one of my favorite little bugs because it’s a great example of a non-pathogenic bacteria that comes in a fun shape and lives a rock n’ roll lifestyle.

this is a cartoon i drew for a cell biology class explaining the life cycle of caulobacter crescentus, which can come in two flavors: as a swarmer or as a stalked cell. a swarmer has a little tail that allows for it to swim around, whereas a stalked cell has a holdfast–or “sticky foot”–which allows for it to attach to solid surfaces, or other stalked cells. swarmer cells the daughter cells of the stalked cells, and swarmers can progress to become stalked cells. only stalked cells can give birth to new daughter cells.

at the tip of a stalked cell’s holdfast is a type of natural adhesive which is freakishly strong, estimated to be 3-4 times stronger than superglue. once the cell attaches to a surface, it’s for life. it’s pretty cute to see these clumps of cells in a culture called a “rosette” because i think, they better like each other because those bastards are stuck with each other until they die.

what’s more–caulobacter lives underwater. this means that caulobacter naturally makes the world’s strongest superglue–and it’s waterproof!

welcome to microbiology.