Microbiology Spring 2007

ally21 · Apr 11, 2007

JDLAStew, that's great you've sorta figured out what your unknown is. Did you have to do other tests to come up with a conclusion? My professor says colony characteristics and gram staining are subjective so we had to do more tests and come up with a reason why we did them. We weren't allowed to streak EMB or Mannitol agars since she said it'd be too easy to narrow down the list. Nice teacher, huh? We're just finishing up ours and I have yet to write my paper. I have until April 16th... Micro has been so stressful and I don't know whether or not to study for the exam or work on the unknown. My professor loves to knock as much points off of us as possible. I pray that I'll pass it this semester so I won't have to ever take it again. It's my last pre-req for the nursing program thank god. Now I'll just have to worry about the nursing classes each semester which shouldn't be so bad.

catzy5 · Apr 11, 2007

JDLAStew, that's great you've sorta figured out what your unknown is. Did you have to do other tests to come up with a conclusion? My professor says colony characteristics and gram staining are subjective so we had to do more tests and come up with a reason why we did them. We weren't allowed to streak EMB or Mannitol agars since she said it'd be too easy to narrow down the list. Nice teacher, huh? We're just finishing up ours and I have yet to write my paper. I have until April 16th... Micro has been so stressful and I don't know whether or not to study for the exam or work on the unknown. My professor loves to knock as much points off of us as possible. I pray that I'll pass it this semester so I won't have to ever take it again. It's my last pre-req for the nursing program thank god. Now I'll just have to worry about the nursing classes each semester which shouldn't be so bad.

I hear ya I am not so much worried about doing the unknown as I am about writing the paper! mine isn't due until May but we have started workig on it and started writing the papers she is very particular about the whole thing.

akspudus · Apr 11, 2007

We finished up our unknowns last week. First week was setting up all the cultures, second week was reading results.

I spent the week in between looking up all the possible test results for each of the bacteria possibilities. (which is a lot harder than it seams)

I think I nailed it all correctly, but I don't find out for sure until tomorrow -> after the written final.

Akspudus

JDLAStew · Apr 11, 2007

I know I'm probably jumping the gun--we just started last night and we plated in agar at 37C and room temp and did one Gram stain. I'll get a little more clarity with each test. We're lucky cause we do get to use EMB, MSA, and MA to determine. I'm with the rest of you--the paper terrifies me! The paper/unknown is 50% of our grade!

prinsessa · Apr 12, 2007

We aren't doing unknowns since the equipment at school isn't working right now. We only had a couple of experiments. I was kind of looking forward to lab since I find this stuff interesting. Now we have to listen to the teacher lecture for hours every night.

GeneralJinjur · Apr 12, 2007

That's too bad about the equipment. I wouldn't mind more lecture time, but it would be exhausting to go for 3 hours every night.

Our school does unknowns differently. We cultured whatever we wanted at the beginning of February and have performed every test on known organisms and our unknowns throughout the semester. My writeup is due Tuesday. It's only a tenth of the total grade, but 100 points is a whole grade point.

akspudus · Apr 12, 2007

We had a lab journal that we had to maintain through the semester -> 20% of your grade.

Then we had our fist unknown. More like a mid term exercise-> 20% of your grade

Our Second unknown finished up last week and this week we had our final practicum -> combined for 35% of your grade.

The rest of our grade came from quizzes and homework.

Found out today that I pulled a 93% overall --> Phew...glad it is all over. I hate classes that throw so much weight into one or two exercise. Feels like you have all your eggs in one basket. Oh well, I guess I should get used to it for NS.

Akspudus

Miami Dade College

Barry University Hopeful

JDLAStew · Apr 13, 2007

I jumped the gun. And I'm stuck and ready to cry...hard. Tonight my gram stain looked pink and some were purple! All I know is that it's a definite rod. It's between B.cereus, B.Subtilis, E.Coli, K.Pneumoniae, and P. Vulgaris. Those are the only rods we grew this year. My agar was creamy white and shiny but it went crazy! Almost my whole plate was full and I did a simple streak. I'm scared to death. If the whole class wasn't in there tonight, I swear I could have cried. I felt that huge lump in my throat forming. I was way too confident before. I don't see how the Gram stain could have gone from such a brilliant pink to almost a light purple/dk. purple. A gram stain of subtilis on the net looked like mine did tonight. I'm scared to death!!!

ally21 · Apr 13, 2007

JDLAStew, relax! Did you make a back up slant of your unknown? It's possible that there was contamination or the gram stain wasn't right. Did the teacher check the first time you did a gram stain to see if you were on the right track? What other tests have you done? I don't have my chart down here from the Bergey's manual so I'm not much help right now... but I think something may be going wrong for you to have gram + and gram - rods in your unknown.

JDLAStew · Apr 13, 2007

I've googled various things....no my teacher never looked at any of our slides even before we started. Her whole deal is pretty much teach yourself. After searching I think I've got it down to either one of the 2 bacillus species. The picture of b. subtilis on wikipedia looks identical to my Gram stain--looks magenta and purple (maybe not so pink??) However, my agar growth looks more like cereus from this website http://www.bact.wisc.edu/Microtextbook/index.php?module=Book&func=displayarticle&art_id=123 in fact, my cereus looks identical to that! We are supposed to use Bergey's during the final too and I have no clue about how to use it and my teacher has never shown us. I have felt very lost all semester and it's across the board with my classmates. I know a lot of people enjoy micro but I've hated it...I've been frustrated and lost since day one! And we didn't make our own slants. She had slants numbered and we had to take it and do a gram stain from it and plate it in NA at 2 different temps. Then start from there. We can do MA, MSA, and EMB but we can't do them all unless we justify why we did them in our paper. And, did any of you have cereus look peach in agar before? When we grew it earlier this semester ours turned peach and I can't find a peach sample anywhere on the interent. I think ours was messed up then so that is throwing me off. Ack! Anyway I'm gonna try to get some sleep and NOT think about micro!

akspudus · Apr 13, 2007

What tests are you running on your unknown? Fermentation? Catalase? IMViC? I had both of those bacteria species as a possibility in my unknowns. I have all the test results from Bergey's compiled into a spreadsheet if you need them.

B. Cereus was one of my unknowns. I had the following test results:

Gram - Pos, Acid Fast - Neg, Endospore - Pos

Lactose Fermentation - neg for acid and gas

Dextrose Fermentation- pos for acid neg for gas

Mannitol Fermentation- Neg for acid and gas

Nitrate Reduction - Pos Citrate Utilization Pos

Starch Hydrolysis - Pos Catalase Test Pos

Methyl Red - Pos

Cultural Characteristics

Pigment - Beige to White Texture - Smooth Size - Large Spreading

Form - Rhizoid Elevation - Flat to Raised Margin - Undulated to curled

Hope this helps....let me know if you need a copy of those spread sheets or have any other questions.

akspudus

P.S. Make sure you take a look online at Gram staining techniques. The staining protocol isn't too hard, but there are some common places people make mistakes. Also, be sure your smear isn't to thick. You should barely be able to tell that there is something there. If you pile to many cells into the smear, then your staining will be unreliable.

JDLAStew · Apr 13, 2007

We get to do nutrient agar, Eosin Methylene Blue, MacConkey agar, and Mannitol Salt. I believe we get to do catalase. Our unknowns could be 1 of 9 and based on colony morphology and the Gram stain, I know I've got one of the 2. My agar plate looks identical to b.cereus, but my gram stain doesn't look like it--more like subtilis. I would appreciate any help. I was up til 5am googling, and checking on ask.com. I'll PM you my email address so you can send anything and everything you have! You can hold me to it, I will help you anyway possible that I can as we go through school! I'm really just upset and worried over this! (Can you tell I freak out, a lot? LOL)