"if a bacterium cannot use citrate, what result will occur in citrate agar? "

If a bacterium cannot use citrate agar will not change its color (stays green). On the other hand, if bacteria have the ability to use citrate, the medium will change its color from green to blue.

This happens because citrate agar contains pH indicator such as bromothymol blue which transforms from green to blue in alkaline conditions.

The answer is it will not change it's color.

A citrate is a derivative of citric acid; that is, the salts , esters , and the polyatomic anion found in solution. An example of the former, a salt is trisodium citrate ; an ester is triethyl citrate .

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.