MICRO 260 Lab 7

which organisms could not grow on the glucose salts medium? which organisms could grow on it?

Staphylococcus is the only organism that cannot grow on the GSA. On ocassion, other cultures will happen to develop a mutation fr a nutritional requirement, preventing their growth on the GSA as well though this is rare.

which organisms do not require any growth factors?

organisms that can grow on glusose salts do not require growth factors. organisms that grow well on TSA plates but not GSA plates DO require growth factors.

of the organisms that could grow on both TSA and GSA, did some organisms grow better on the TSA? Reason?

Organisms generally grow better on a complex medium such as TSA because they do not need to synthesize as many growth factors or other cell constituents.

Which organisms could grow on the EMB agar? how?

Echerichia coli, Enterobacter aerogenes, and Pseudomonas aeruginosa can all grow on EMB agar.

which organisms could ferment lactose?

E. coli and E. aerogenes can ferment lactose, but NOT P. aeruginosa. It cannot be determined whether Staphlococcus can ferment lactose because it cannot grow on EMB.

could you differentiate E. coli from other organisms growing on the EMB agar? how?

E. coli produces purple colonies to indicate that it ferments lactose. It also produces a green sheen in the agar because of the large amount of acid resulting from its particular fermentation pathway.

In gerneral, EMB agar selects for what kind of organisms?

EMB selects for Gram-negative organisms.

what kinds of organisms does EMB agar differentiate?

EMB differentiates from lactose fermentors and non-fermentors.

GSA

Glucose Salts Agar. simple CHEMICALLY DEFINED medium. only organisms that can synthesize all of their own from glucose and inorganic salts grow on it.

TSA

Trypticase Soy Agar. rich, complex medium.

EMB agar

Eosin Methylene Blue Agar. SELECTIVE medium permitting growth of Gram Negative cells DIFFERENTIAL-distinguish those that ferment lactose and those that do not.

Fastidious

needing many growth factors.