The six bacteria used in this lab were, Citrobacter freundii, Bacillus subtillis, Enterobacter aerogenes, Staphylococcus epidermis, Enterococcus durans, and Escherichia coli. Citrobacter freundii is a Gram-negative rod shape bacteria.
The MSA plate will grow Citrobacter freundii, Bacillus subtillis, Enterobacter aerogenes and will have a yellow color change while Staphylococcus epidermis will not grow nor have a color change to yellow. The MacConkey agar will have growth with Escherichia coli, Enterococcus durans, but not Staphylococcus epidermis and Bacillus subtilis since it is a Gram-positive. Only Escherichia coli and Enterococcus durans will be the species fermenting. PEA agar isolates Gram-positive species from Gram-negative bacteria.
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The agent used was called tetramethyl-p-phenylendiamine. When reduced the agent was clear but when oxidized it turned deep purple to a blackish color. This agent (Cytochrome C Oxidase) was the electron donor. This test did not distinguish whether the organism is oxidative or if it fermented.
In the Oxidative fermentation tube the media was a differential media that helps determine whether specific bacteria can oxidize or ferment to metabolize glucose.
Citrate test checks to see which bacteria could citrate as the only source of carbon. A positive test shows that an alkaline environment ia created and that the pH level rose. The color of the media changed from green to blue if its positive.
The Bile Esculin agar test has its medium as selective and differential. Black medium shows a positive result for esculin hydrolysis. In the agar, Gram-positive cannot grow in the presence of bile while certain Gram-negative bacteria can hydrolyze esculin with bile present.
MR-VP broth contains glucose and peptone. The enteric bacteria will oxidize glucose for ATP, but there are different fermentative pathways that allow glucose to be fermented. The type that ferments acid would ferment a variety of acids like lactic or acetic