Most changes in oxidation states of elements that are nutrients in the biosphere are mediated by microorganisms. B. Understanding of the dynamics of nutrient cycling and the ability to predict the availability of nutrients to crops in organic cropping systems would be greatly improved by recognizing that these are microbial reactions. I. Nutritional requirements and key anabolic pathways. Carbon obtained from organic compounds or CO 2 . 2. Nitrogen a. Nitrate commonly used.
Some organisms assimilate ammonia by incorporation into amino acid glutamate .
Fixation of atmospheric N 2 by some organisms. Sulfur primarily from inorganic sulfate which is reduced in cell to H 2 S and incorporated into amino acid cysteine. Polysaccharides from sugars 2. Proteins from amino acids 3. Nucleic acids from nucleotides 4.