Most structural genes of bacteria are grouped together and transcribed from a single ; immediately following this sequence is the that interacts with a regulatory protein to affect transcription of the genes. A. gene; promoter B. ribosome; promoter C. promoter; operator D. promoter; structural gene E. regulon; operon

C. Promoter; Operator

Explanation:

Related genes in bacteria are often found in a cluster on the chromosome, where they are transcribed from one RNA polymerase binding site(promoter) as a single unit while other regulatory proteins are binding repressors attached to DNA pieces known as operators. When they are bound to operator, a repressor reduces transcription.

Genes in cases like this encode proteins, having various roles which include fuel metabolism, maintenance of cell structure, and

also defense against viruses in its process. A great number of these proteins are been used while others are needed only under certain decrees. Therefore, it is said that cells don't express all the genes in their genome always.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.