zoidia

From my notes it says in your TSI, if the butt turned yellow it means glucose was fermented. So its yellow and you said the it was negative for the Citrate tube, and left with a blue slant (not green which is positive) . So, if your Citrate remained blue it could be Enterobacter aerogenes. If it was green- e coli... hope this helps

I only need help with my gram-postive bacteria. Anyway, my enterococcosel agar plate is mostly yellow, but where i have streaked the plate looks like its white but there are no specific colonies growing just where i have streaked the plate. The spot that is black is still white streaks but around the streaks is black. So all the possible gram-positive bacteria to chose from are: Bacillus megaterium (no), Staphylococcus aureus (maybe), Enterococcus faecalis (maybe) and Staphylococcus epidermidis (nope, i dont think at least). The only bacterium that turns the palte black is Enteroccus faecalis. -thx zoidia

So i have a very big delema. What i'm basically doing is taking an unknown culture (says theres only just 2 types of bacteria) and growing it on specific and differencial mediums to conclude which two types i have. So i may have one gram-postive and one gram-negative bacteria in the culture tube. First, i inculate PEA (phenylethanol agar) which is particularly for isolation of gram-postive bacteria. Then i inoculate EMB (Eosin Methylene Blue agar) is a selective medium for gram-negative bacteria. So after incubation i have postive growth on both mediums. Now i take both plates and inoculate MSA (Mannitol salt agar) from the PEA (if the MSA is fermented the pH of the medium is lowered and the medium turns yellow, which is typical of Staphylococcus aureus and under heavy inoculation Enterococcua faecalis but not Staph epidermidis. Also i inoculated Enterococcosal agar, which is a plated medium to identify enteric cocci. This differential medium in that enteric cocci turn this agar black which signifies the hydrolyzing of esculin. Other organisms may grow on this plate but will not turn the color of it. There was positive growth on my MSA plate So it turned yellow meaning its acidic. Now i look at my enterococcosel plate AND IT WAS MOSTLY YELLOW WITH A LITTLE TINY SPOT OF BLACK!!! Not the kind of thing i wanted to deal with since this project is very crucial to my future. My professor is not allowed to help any student out with this assignment but he was nice enough to give us a clue.. and so i told him the 2 types of bacteria i think it is and he said one of them is wrong. Well for sure gram-negative bacteria is right which is Proteus Vulgaris. And the other answer is gave him was the bacteria that made the enterococcosel agar mostly not black which would be Staphylococcus aureus, and its not right!!! So now i'm thinking the bacteria that made the little spot of black is right which is Enterococcus faecalis. I dont know why or how or what im so lost. I would be very appreiciated if someone could help me out.. after i conducted this experiment i came to conclusion that i have the correct gram-negative bacteria right but not the gram-postive. Here is a flow chart of how i think i got to the gram-postive PEA- MSA - Growth or no growth (was growth)- Yellow or not yellow (yellow)- Enterococcosel plate - Black or not black- IDK!!?? Black??