Why is nitrogen, sulfur, and phosphorus needed for the chemical requirements of microbial growth?
Nitrogen makes up 14% of the dry weight of bacterial cell, and sulfur and phosphorus together constitue about another 4%
Nitrogen is primarily used to form the amino group of the amino acids of proteins.
Sulfer is used to synthesize sulfur-containing amino acids and vitamins such as thiamine and biotin. Important natural sources of sulfur: sulfate ion (SO42-), hydrogen sulfide, and the sulfur-containing amino acids
Phosphorus is essential for the synthesis of nucleic acids and the phospholipids of cell membranes. phosphate ion (PO43-)