Question

A bacterial culture is being tested for its ability to reduce nitrate. After incubation and growth of the bacteria in nitrate broth, there is no accumulation of gas in the Durham tube. The test for the presence of nitrite is colorless. When zinc powder is added, a bright red color develops. Interpret these results.

Answer 1

All this combination of reactions is summarized in that the bacteria reduced nitrate, that is, they added protons to said compound, giving nitrite as a product.

By promoting the appearance of nitrite and that it increases in its concentrations when the zinc dust is thrown away, it becomes reddish since there was a change in pH, that is, the medium was acidified.

Step-by-step explanation:

Some bacteria take nitrate as a source and end up generating an oxide reduction reaction that gives nitrite as a product, if this reaction advances in a chain, that is, the nitrite is reduced after the nitrate, the product in the future would be ammonia