ABSTRACT
Soil is an ecosystem that contains a variety of microbial populations whose members
represent many physiological types. For example, some microorganisms, such as fungi, are
aerobic chemoorganotrophs (heterotrophs) and use organic compounds as a source of carbon
and energy. Others, such as nitrifying bacteria, are aerobic chemolithotrophs (autotrophs)
using CO2 as a carbon source and oxidizing reduced inorganic N compounds to obtain
energy. Some microorganisms require special growth factors, a specific environmental pH,
low O2 levels, or the absence of O2 (i.e., anaerobes) for optimum growth. The chemical,
physical, and biological characteristics of a particular soil, as well as the presence of growing
plants, will influence the numbers and activities of its various microbial components.
Furthermore, because of the heterogeneous nature of soil, many different physiological
types of organisms will be found in close proximity to one another. The microbial commu-
nity in soil is important because of its relationship to soil fertility and the biogeochemical
cycling of elements, and the potential use of specific members for industrial applications.
Thus, there is a need to enumerate and isolate major and minor members of the microbial
community in soils.
