Microbiology Spring 2007 - page 23

:welcome: Gonna try to stick this one!!! Heres to a wonderful semester for all us MBers :):welcome:... Read More

  1. by   JDLAStew
    After reading all about all your unknowns and whatnot, I feel bad for complaining! I should be grateful. Ours in 1 of 9 and no mixed cultures. After going through my notes and Akspudus', I'm pretty sure it's B. cereus....but of course I won't know for sure until my tests are done. At this point, I'm just dreading the paper--it's a minimum of 18 pages with no internet sources. Ick. Since I'm starting to complain again, I'll quit and be grateful that mine isn't as near as hard as the ones you all have.

    Good luck to everyone. Just a few more weeks left, right?
  2. by   ally21
    18 pages?! Double spaced? Mine came out to 7 pages single spaced. My teacher didn't want us to go overboard with explaining the procedures. We just had to explain why we did each test. Gram staining knocked a great majority off the list, then I did a streak plate, then the catalase test which helped me get down to just 3 unknowns. I was able to narrow it down to my final unknown by doing the MRVP tests. My teacher likes to knock off lots of points for stupid things. If we did a test that wasn't appropriate from the research on our unknown bacteria she'd probably deduct points for it. I'm glad it's over with because it took me almost 8 hours to finish the paper and I handed it in today. We had to figure out our unknown out of a list of 36 possibilities.
  3. by   np_wannabe
    Quote from np_wannabe
    We just inoculated our cultures today, and I'm worried about my gram stain. I left the ethanol on for about 30 seconds, instead of about 5. I keep reading places that say you can't leave it on too long because of XYZ, but does anyone know how long is too long? I have a G- rod, but I'm just not sure if i screwed it up or if that is reliable....anyone know how long is too long??? I'm going to see what I can find over the next couple of days, if I can't find anything that says I'm okay, I'm going to ask if I can do another stain.

    I hope someone out there has some idea...
    I read my media today--I definitely have E coli, so my G- stain was right! If anyone out there leaves there ethonal on for a little too long, it's okay...
  4. by   me33
    I have a lab test tomorrow and was wondering if anyone knows what the substrate is for MRVP test. Is there one substrate for the MR and a different one for VP? I can not find the answer. He has these questions on a study guide. Any help would be greatly appreciated.:spin:
  5. by   akspudus
    Both the Methyl Red (MR) and Voges Proskauer (VP) tests use the same media. MR-VP media. Its same media for both tests. Different reagents obviously:
    Methyl Red for MR Test
    Barritt's reagent (Parts A and B) for VP Test

    Hope this helps. Let me know if you need more. I think I have the actual MRVP recipe somewhere.

    Akspudus
  6. by   me33
    Thanks for your help. I did have those as reagents but he is also asking for substrate. What do you think because I can not find the answer for a substrate
  7. by   JDLAStew
    I thought I had this thing licked. Tonight, my gram stain looked Gram positive. At this point, all I have for sure are rods. My EMB turned out pinkish/purple with a yellow halo?!?!?! My MacConkey had a slight bit of pink growth were I started and then went to nothing at the bottom. I haven't completed my last plate which is Mannitol Salt. My nutrient agar growth is creamy white/buff, shiny, flat. And like I said rods. Does anyone know why my EMB turned out this way? It doesn't make sense with any of my previous results. Yep, there they are...there's the tears.
  8. by   akspudus
    Hmmm....You can rule out E. Coli. E. Coli forms a metallic green sheen on the surface of its colonies. A for growth in EMB, only gram-negative bacteria grow on EMB agar. Gram-positive bacteria are inhibited by the dyes eosin and methylene blue added to the agar. Enterobacter produces large, mucoid, pink to purple colonies with no metallic green sheen on EMB agar.
    The yellow halo you see is an area where nutrients have been used and depleted from the agar.


    So I would be thinking E. aerogenes.

    E. aerogenes growth on MacConkey Agar is described as good to excellent with a pink to red mucoid apearance.

    And Yup...its a rod shaped bacteria.



    So....my money is on E. aerogenes. You need to do some carbohydrate fermentation tests...and Methyl Red (MR) and Voges Proskauer (VP) tests to be sure.


    Hope this helps.

    akspudus
  9. by   JDLAStew
    one problem, we don't have e. aerogenes. and we can only do one more plate, mannitol salt. we are only allowed to do nutrient agar, emb, ma, and msa and 2 gram stains..and a catalase test. i was catalase positive. the only microbes we received were 1 of the following 9:
    bacillus

    cereus
    bacillus
    subtilis
    escherichia
    coli
    klebsiella
    pneumoniae
    micrococcus
    luteus
    micrococcus
    roseus
    proteus
    vulgaris
    serratia
    marcescens
    staphylococcus

    epidermis
    any ideas??
    Last edit by JDLAStew on Apr 19, '07 : Reason: Forgot the ending...whoops!
  10. by   akspudus
    Dang....no E. aerogenes...that kinda bights. Hmmm....its got to be Gram negative for it to grow on EMB. Gram Neg bacilli. E. Coli is already ruled out since you didn't get a metalic green color on your EMB. So that leaves K. Pneumonia, S. marcescens or P. vulgaris. Both K. pneumonia and S. marcescens have blueish purple color characteristics on EMB.
    Your mannitol salt should end up showing no growth.
    S. marcescens is aerobic - catalase positive.
    P. vulgaris is aerobic - catalase positive.
    K. Pneumonia is anaerobic - catalase negative.

    So...
    Most likely it is P. vulgaris based upon your observations.

    Akspudus
    Last edit by akspudus on Apr 19, '07 : Reason: Spelling
  11. by   JDLAStew
    It doesn't look "swarming" yet the bacteria really grew in size on the plate. You can see my streaks then it really forms large colonies out from it. Very shiny and flat. It resembles b. cereus in the agar but with everything I do it looks like it could be something else. I'm about to start writing the paper on one of them and pray I get it right. My friend and I had a good breakdown cry tonight. She's stuck on hers but I would be money hers is B.subtilis--well with the except her EMB looked like mine. The purple-ish color with the yellow halo look. Her's is dry, mine is shiny. I'm sorry for explaining this junk over and over. My hubby has no idea what I'm talking about and this seems to be my only vent area. Other students will look over at what I have and say, no that's not what you have--I'm sure I have that and yours doesn't look like it. ACK! Do they think that helps? Anyway I'm off for a small weekend trip. Will be back Sunday. Have a good weekend and thank you Akspudus for ALL of your help. I mean it.
  12. by   catzy5
    Quote from JDLAStew
    It doesn't look "swarming" yet the bacteria really grew in size on the plate. You can see my streaks then it really forms large colonies out from it. Very shiny and flat. It resembles b. cereus in the agar but with everything I do it looks like it could be something else. I'm about to start writing the paper on one of them and pray I get it right. My friend and I had a good breakdown cry tonight. She's stuck on hers but I would be money hers is B.subtilis--well with the except her EMB looked like mine. The purple-ish color with the yellow halo look. Her's is dry, mine is shiny. I'm sorry for explaining this junk over and over. My hubby has no idea what I'm talking about and this seems to be my only vent area. Other students will look over at what I have and say, no that's not what you have--I'm sure I have that and yours doesn't look like it. ACK! Do they think that helps? Anyway I'm off for a small weekend trip. Will be back Sunday. Have a good weekend and thank you Akspudus for ALL of your help. I mean it.

    Are you kidding? don't apologise this is helping me! I can't help you I am not that far yet we just started our's I apprectiate hearing your tests and what you have.

    I am frustrated with mine as wll, seems like my stainings weren't coming out very well yesterday I couldn't gram stain at all, My negitive came out ok and I am fairly certain we have no spores but thats about it.
  13. by   catzy5
    [IMG]aoladp://MA17259846-0001/P1000377.JPG[/IMG]

    So I am not sure if anyone can help me but the Large tube is my FTM What would you say the oxygen requirements are? Faculative aneorobe? We don't have any strict aneorobes. So why is there no growth at the top? What have I done??

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