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HELP! Identification of unknown gram-positive bacterium!?

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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HELP! Identification of unknown gram-positive bacterium!?

Postby MGremillion » Fri Apr 01, 2011 9:24 pm

I've been given an unknown organism in my microbiology class that needs identification. My grade is dependent on it! The tube of broth I was given appears a slightly off shade of clear and upon agitation turns turbid with a white growth "tornado-ing" from the bottom. No sediment has been noted. I've performed a gram stain which came back gram positive and the organism appears cocci but my instructor is telling me to "seriously question that". The shape that is. So I assume it's bacilli though it looks cocci. The rest of the results from biochemical tests ran are as follows:

SIM (-)
Glucose (+)
Sucrose (+)
Lactose (-)
Mannitol (-)
Gelatin liquefaction (-)
Fluid thiology - Growth at the top = Aerobic
Slant- White, opaque, medium growth; Round colonies- Effuse
Acid-fast (-)
Catalase (+)
Phenylalanine deominase (-)
Urea (-)
Citrate (-)
Gin's stain (-)
Methyl red (-)
Voges-proskauer (-)
Litmus milk- Alkaline (Incubated 5 days)
Starch (-)
Nutrient agar plate- Circular, flat, entire, amorphious, mucoid
Oxidase (-)
Casein hydrolysis (-)
Nitrate (-)
Tryptone broth (-)
Spirit blue agar plate (-)
DNase (-)

May or may not be positive for spore formation. Really hard to tell.

Please help!?
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Postby JorgeLobo » Thu Apr 07, 2011 12:48 am

It's your unknown and your work. Good luck.
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Re: HELP! Identification of unknown gram-positive bacterium!?

Postby MGremillion » Sat Apr 09, 2011 9:50 pm

Perhaps I should have indicated more so the effort I have put in thus far in trying to determine just exactly what my organism was so I wouldn't have been met with such a lack of caring and sarcasm when I merely came here to receive help like everyone else. With this being a basic microbiology course, I have limited knowledge of the various organisms out their but I know when beginning with identification to start with the fact that it's 1.) a bacterium, 2.) bacillus (apparently), and 3.) gram-positive. Using this criteria I have used the Bergey's manual and come up with several options but have yet to be able to narrow it down; this being in part because I'm having trouble finding a diffenative list of every characteristic for each organism. So far, however, I know it can't be Bacillus cereus because the given organism is non-motile. Same applies for Listeria monocytogenes which is disappointing since I found they are coccobacilli which I thought could be the answer to my shape dilema. From what I've read all criteria match for Bacillus anthracis but I'm positive she didn't give me anthrax. =] Currently I'm leaning the most toward Corynebacterium diptheriae or Corynebacterium xerosis. Would this be a step in the right direction?

On a seperate sheet of paper I've been using to write possibilities and ideas I have also listed the following the research further:
Weissella confuse
Ersipelothrix rhusiopathiae
Lactobacillus
Nocardia
Streptobacillus moniliformis
Propionibacterium acnes
Lactobacillus plantarium
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Re: HELP! Identification of unknown gram-positive bacterium!?

Postby MGremillion » Sat Apr 09, 2011 10:10 pm

Wednesday in lab I went ahead and streaked my organism to a blood agar plate to obtain further information and check for beta hemolysis and growth characteristics. Are there any other biochemical tests I might consider running?
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