Friday Facts: Bacillus subtilis edition

Hello and happy friday everybody! This week hit me like a truck. I moved into my new place Tuesday night (after an early morning progression run).  Moving was, predictably, miserable; however, I think I am through the wilderness: all that’s left is some unpacking and decorating.

My new nick-name

I rented a pick-up truck to move my bed, and managed to lose a few milliliters of blood in the process. Note to self: optimism and stubbornness are no match for the laws of geometry and physics. If the bed won’t fit you must disassemble it!

Maybe if I TRULY believe, this will work
You win, physics

Now that I have disgusted and amused you all with my incompetence, let me attempt to redeem myself with a (hopefully) educational and informative blog post. During my run this morning I thought it might be fun to write a little post about the bacteria that I work with every single day: Bacillus subtilis.

Wearing compression and thinking about Bacillus. Typical day for me.

Bacillus subtilis is a Gram-positive, aerobic, motile rod. In plain english that means that these little bacteria have thick cell walls, they are good at swimming, they LOVE air, and they are shaped like rods. This is what they look like underneath the microscope:

Cute, right?
I don’t really look at my cells under a microscope very often. When I work with them they are usually growing on plates like this:
Some of these guys are mutants, that’s why they are smaller and sicklier looking
They also like to grow in liquid culture. If you put a bacterium into a flask full of lots of nutrient-rich broth it will start to divide and divide and divide until you have lots more bacteria! This flask probably has about five billion Bacilli swimming around in it.
They are swimming in a broth called LB, which they love.
Picture a swimming pool full of chili
B. subtilis lives all over the planet, mostly in dirt. You may have heard of B. subtilis’ nasty cousin: Bacillus anthracis, which is the etiological agent of anthrax.
We all have relatives that we are embarrassed about. B. anthracis carries around two extra pieces of DNA called plasmids (more on plasmids in a later post) that enable it to make anthrax toxin (and terrible hair metal music). B. subtilis could never cause that disease because it lacks those plasmids and thus the genes for toxin production. It just doesn’t have the equipment, so to speak.
B. subtilis is totally harmless to humans. In fact, B. subtilis is used as disease-reducing agent in organic farming! (This was first described in 1989 [Pusey, P. L. (1989), Use of Bacillus subtilis and Related Organisms as Biofungicides. Pestic. Sci., 27: 133–140]) The idea is that, because Bacillus lives in dirt, it makes all sorts of interesting compounds to compete with the other organisms that also live in the dirt around it. Some of those other bugs (like fungus) are pathogens that cause rot and blight in our fruits and veggies. Farmers can add Bacillus to their crops to kill those nasty funguses instead of using chemical fungicides.  Here’s a link to a nice article that rounds up some of the uses and sources for Bacillus in organic farming.
In the biology world B. subtilis’ claim to fame is that it forms spores. If you are using B. subtilis in farming, or being fed B. subtilis as a probiotic spores are where it is at. This is an aside, but I am I am skeptical of this probiotic thing. Bacillus needs air to live, and there isn’t a whole lot of air inside your digestive tract…I guess this paper [Fujiya, Cell Host Microbe, 2007] demonstrated that B. subtilis makes a signaling molecule that can influence cells in your intestine (nice explanation in laypersons terms here), and they do make some interesting molecules with purported antioxidant properties; however, I’m not 100% convinced that the bacteria in that probiotic pill are going to survive and thrive inside of you.
Spores are SUPER cool. When B. subtilis runs out of food, or runs out of air, or gets stressed out it starts making some changes. Instead of growing like normal rods they start making a thick coat and shutting down all of their processes to enter a totally dormant state.
The spores are the green guys (image: wikimedia commons)
Why do the bacteria do this? Becoming a spore is a survival strategy. Spores are INCREDIBLY TOUGH. You can boil spores for 10 minutes: they don’t care. You can blast spores with crazy high doses of UV, throw them in bleach, or practically drop an atom bomb on them and they still survive (for a nice review see [Setlow, Journal of Applied Microbilogy, 2006]). In one of my favorite uses of taxpayer dollars EVER, a group sent B. subtilis spores into outer-space for a year and a half [Nicholson, Astrobiology, 2012]; the spores germinated and grew completely normally when they returned to planet Earth. Basically- when times get tough for B. subtilis, the get tougher. The cells hunker down as spores to wait until conditions improve. Spores are nothing if not patient, one group was able to resurrect some spores that they found buried in a 250 million year old salt crystal! [Vreeland, Nature, 2006]!
There are spores in here….(image from [Vreeland, 2006])
I don’t work on sporulation. I am interested in how bacteria copy their genomes, and because spores are totally quiescent, they aren’t copying their DNA at all.
Whenever I make a cartoon of what I work on, it looks like a space-ship….
I think that’s enough of an introduction to my friend Bacillus for now. I’ve barely scratched the surface about all of the amazing things that this organism, and other bacteria, can do. If you have any questions, please leave a comment. Next time I think I’ll talk a little more about how bacteria copy their DNA, and some of the amazing things we have been learning about evolution. Until then, I hope everybody has a fantastic Friday! Stay classy earthlings! This American is off to grow some cells, make some RNA, and later brave the wilderness of Bed Bath and Beyond
What are YOU up to this Friday?
Do you take probiotics? 

16 thoughts on “Friday Facts: Bacillus subtilis edition

Add yours

  1. No probiotics in this household, if you are keeping count of who does what in Blogville.

    I don't have a substantial background in science, but now that I am older and not being graded I have to say I find it really interesting. I just spent a year and a half thinking about clostridium perfringens as a general bacteria and specifically as a food poison. Seems I should have talked to you sooner — your blog answered some questions that were confounding to me along the way. Hence my comment to you before that the science world could use some people who write well.


  2. Lori- If you EVER have a question about science feel free to email me! Like I said, I don't know everything about everything, but I'm full of opinions and I usually know where to look to find the answer.

    I didn't know you were thinking about Clostridia! They are ALSO gram positive spore formers, like Bacillus. Clostridia are obligate anaerobes, though…they die if they get exposed to air (unless they are being spores). Apparently they are SUPER difficult to work with, too.

    I don't believe in pro-biotics, but I do believe in eating naturally fermented foods like sauerkraut. There have been pretty convincing studies showing that the bugs in delicious kimchee actually can perturb your micro biome for the better.


  3. I actually thought of contacting you early on in my Clostridia education. I will tell you about it when next we get to chat over the fence. :)


  4. Hi
    I took a digestive enzyme which unfortunately contain bacillus subtilis and I feel it has messed up my whole life gut flora and digestive system. What do I do now?



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