So, I promised cool bacteria pictures, and I shall deliver!
Since I’m taking microbiology, I’ve naturally been learning a ton of cool stuff about bacteria. Let me just say – bacteria are wily little bastards. Considering they are unicellular and prokaryotic (aka they’re single celled and don’t have a nucleus, so you’d think they wouldn’t be very smart), they are extremely adept at surviving no matter what and taking us down in the process. Even after they die, they leave their DNA behind so that other bacterium can pick it up and use it to survive the environment. That is just crazy! I could go on and on about the nutty things I’ve learned, but suffice it to say:
I am now a huge germophobe.
In lab, we’ve been learning how to do a lot of different tests to see exactly what different bacteria can do. I guess in real clinical laboratories, they use these tests to help diagnose patients who have unknown bacteria chilling in their systems. We’re doing them just to learn the processes and to learn hands-on what different bacterium are capable of. It’s pretty cool! So here are some examples and pictures I took with my phone during class (my professor is pretty awesome about letting us do stuff like that. My friends have gotten so many disgusting Snapchats this semester…if anyone hacked my Snapchat, they are definitely sorry!!).
First up, the urease test. We did this one to see if our bacterium makes the enzyme urease, which allows it to digest urea. A lot of bacteria make urease, but only a few make it and use it fairly quickly, so it’s a useful differential test to see if the bacterium you’ve collected is one of these pathogenic (disease causing) ones. What you do is put the bacterium in a test tube with urea, phenol red, and some other stuff, which all makes up a liquidy broth. If the bacterium can digest urea, it makes urease, excretes the urease into the broth where the urease actually digests the urea outside of the bacteria’s cells. As it digests, it makes ammonia and carbon dioxide (sort of like we make poop). The bacterium absorbs the nutrients it needs, and in the meantime, the ammonia turns the phenol red that’s mixed into the broth into a neon pink.
When our professor told us that our positive tubes would be neon pink, I kind of didn’t believe her. I figured they’d be pinkish, but not neon. I don’t know why I thought this – I’m a total idiot, because our tube literally, actually turned hot pink! It was the coolest thing ever!
Nextly, the swabs. We took sterile swabs and cultured our noses, hands before and after washing, and fingernails. We also did throat cultures on ourselves and grew those on separate plates.
Yes, I actually did a strep test on myself, in the classroom, and I did not throw up all over the floor. I was ridiculously proud of myself!
Here’s a picture of my plate with the four different swabs (NOT the throat culture):
For funsies, take this poll and guess which of the four swabs had the most growth. Answers will be at the end of the post!!*
And, finally, I’ve saved the coolest/grossest for last! I still have this picture saved on my phone and randomly ask people if they want to “see bacteria.” You’d be surprised how many people say yes!
This test was called the starch hydrolysis test, and it’s done to see if bacteria can digest starch. Starch molecules are fairly large, and they can’t be taken into the cell for digestion, so a bacterium needs to be able to make an enzyme that goes outside (just like with urea – an enzyme that does this is called an exoenzyme) to digest the starch into smaller chunks and then bring it inside. The stuff on the plate (called agar) that we put the bacterium on has starch in it, so all we had to do was leave the bacterium on the plate for a while and then see if they had eaten the starch around them.
However, since the agar is kind of clearish, we couldn’t really tell if there was a clear area around the bacteria where they’d eaten away the starch or not. So our professor had us pour iodine, which is really dark, on top of the plate. Iodine can’t stick to the products left behind after starch is digested (again, think poop), so if the bacteria had eaten up the starch, there would be what my professor called a “halo” around them. If they had not eaten the starch, the iodine would cover the plate completely.
I knew this was going to be super cool the minute she described it, and I was absolutely right! Here’s what our plate looked like. Can you tell which bacteria digested the starch?? I’m betting you can!
Honestly, this was one of the most amazing things I’ve ever done in a class before. I thought these bacteria were so beautiful – hot pink, creating halos…even the language is full of words we associate with beauty. I can’t wait until next semester when I take Food Science and learn how this all ties in with nutrition. But for right now, I’m enjoying learning about it for it’s own sake (you know, except for the whole wanting-to-live-in-a-plastic-bubble thing).
*Swab Colony Answer: the only section of the plate that had significant growth was from under my fingernail. Look at all those bacterial colonies! If you take one thing away from this, let it be: NEVER BITE YOUR FINGERNAILS AGAIN!!! DON’T PUT YOUR HANDS IN YOUR MOUTHS, PEOPLE!
I mean, look at that! Ew!! Even inside my NOSE was cleaner than under my fingernail!