Approximate Composition of a Microbial Cell ( Dry Weight) Sodium 1% Calcium 0.5%, Magnesium 0.5%, Chlorine 0. 5% Potassium 1% Iron 0.2% All others.3%6 Sulfur 1 1% Phosphorus 3% Hydrogen 8% Nitrogen 14% Carbon 50% xygen 20%