Wednesday, July 16, 2008

Good News, Mr. Yen-- It's An E. Coli!


Last week, my lab partners and I ran various tests on both gram negative and gram positive bacteria and recorded the results. Last week we were each issued an unknown bacteria sample and we had to first figure out whether the bacteria was gram negative or positive, and then run the appropriate tests.

After determining last week, through gram staining, that I had a bacillus-shaped (rice-shaped) gram negative bacteria, I ran the gram negative tests on it.

As I ran the tests, I expressed the hope that my unknown was E. Coli, mainly because E. Coli has a unique result in the Easion Methylene Blue (EMB) test; the culture turns a really cool metallic green.

As you can see from the picture, I got my wish. When I took my cultures out of the incubator this morning, my EMB test was metallic green, indicating the likelihood that my unknown bacteria, whose current name is "Unknown #24," is E. Coli. This conclusion was bolstered by the fact that it also turned the McConkey agar dark pink, indicating a lowering of pH caused by the fermentation of lactose.

My Triple Sugar Iron (TSI) "stab and streak" test, which is a differential test-- it tests for multiple things-- mostly backed up my E. coli conclusion. The slant was yellow, indicating that the bacteria metabolized lactose and/or sucrose, which is consistent with E. Coli. The "butt" was not black, indicating no hydrogen sulfide production, again consistent with E. coli. and there were bubbles in the "stab" portion, indicating carbon dioxide production, again a sign that Unknown #24 is E. coli.

The only inconsistent finding was that the "butt" portion, the bottom of the test tube, was red, rather than yellow. If it is E. coli, it should ferment the glucose in that portion of the test tube and turn the agar yellow due to a change in pH. My professor said not to worry-- give it an extra day; it sometimes takes an extra day for that to turn.

Man, I love this stuff!

13 comments:

Cheer34 said...

you are speaking a foreign language

SkylersDad said...

If the butt turns red, that is generally a sign of Baboon coli.

JR's Thumbprints said...

That's when learning is fun--when you discover that you really really know how to do something!

Suze's Sass said...

Well, as long as you didn't find it inside your refrigerator, I'm happy for you.

kirby said...

It's almost pretty.

Coaster Punchman said...

I wish I did something useful like this. And I'm not being sarcastic even though that may have sounded like it.

Dr. Monkey Von Monkerstein said...

Way to get all technical on our asses.

Mnmom said...

Thank you Spock, now run that sample down to McCoy and see if he concurs.

Natalie said...

Lab stuff is really fun. Its the only thing i miss about science.

Cap'n Ergo Jinglebollocks said...

OK, I vaguely understood about 80% of this from my days in bio and working in a hospital. I have two questions:

1) it's E-fucking coli! Why in the hell are you playing with this stuff?!

2) why ARE you doing this labby stuff again? I've forgotten: you're studying for a job change, right? I remember you as a teacher and then a waiter, so this has got to be some sort of career move for better work and pay, right? (it' better be! You're playing with E-fucking coli!!)

DivaJood said...

Geez, Mr. Yen, I thought it was some funky asparagus.

Tenacious S said...

I love agar, petri dishes and bacteria much more than I know I should. It's only thanks to my lack of mathematical skill that I am not holed up in a lab somewhere. Ask me sometime about my my 1st place finish in the state science fair in eighth grade. Only a lab junkie would find it amusing. And yes, I am a giant closet science geek.

purplelar said...

That looks like something in the back of my refrigerator. I think they were peaches . . .