Alfred R. Conklin, Jr., Soil Sediment and Water, 2002
Soil scientist define soil microorganisms as any organism in soil which requires a microscope to observe. These organisms ranges from bacteria to nematodes and includes diverse species of algae and protozoa. Soil microorganisms are responsible for the breakdown of organic matter, including hydrocarbons, conversion of inorganic components from one form to another and the production of humus. Although this group is large and diverse, soil microorganisms are thought of as being of three distinct types: fungi actinomycetes, and bacteria. Soil microorganisms form a robust community capable of surviving and functioning under extremes of temperature, water availability, pH, energy resources, nutrient availability and salt concentration.