Some microorganisms, especially the pathogenic one, need special growth factors such as vitamins, fatty acids, amino acids or factors from animal blood. Carbon is the basic element that all cellular macromolecules are made from. Some cells may obtain carbon in the form of glucose or other nutrients. Some cells obtain carbon from atmospheric CO 2 .
Nitrogen fixing bacteria are essential for soil fertility.
Microorganisms need nitrogen to make amino acids, the subunits of proteins. This is often a limiting nutrient for microbial cells that live in the environment. Phosphates are needed to sythesize ATP, RNA, DNA and other needed molecules. Oxygen is obtained from water or from atmospheric O 2 . 1. These microbes lack superoxide dismutase, and catalase or peroxidase, enzymes that rid cells of H 2 O 2 and oxygen radicals.