Question

why does this positive test turn blue?

Negative Positive Select one: O a. O2 reacted with Na+ in media to Na03 O b. CO2 reacted with Na+ in media to NaCO3 OC. CO2 reacted with Na+ in media to NH3 O d. CO2 reacted with Na+ in media to Naci

Answer 1

I = indole production. This test shows wheather bacteria can utilize aminoacid tryptophan to make pyruvate. Indole is byproduct of reaction.

SIM (sulfide, indole, motility) medium is an example of a multi-test medium that is it tests more than one aspect of the bacterium's metabolism at a time. In this case, the production of hydrogen sulfide, the formation of indole and motility.

SIM media is a differential medium. It tests the ability of an organism to do several things reduce sulfur, produce indole and swim through the agar (be motile). SIM is commonly used to differentiate members of Enterobacteriaceae.A positive motility test is indicated by a diffuse zone of growth flaring from the line of inoculation. A negative motility test is indicated by growth confined to the stab line. A positive test for indole is denoted when a pink to red color band is formed at the top of the medium after addition of Kovacs Reagent.SIM test is primarily useful for differentiating Salmonella and Shigella. SIM medium contains nutrients, iron, and sodium thiosulfate.If an organism can reduce sulfur to hydrogen sulfide, the hydrogen sulfide will combine with the iron to form ferric sulfide, which is a black precipitate.