The data of long-term investigations on the geographical distribution
of microorganisms of different groups in the main soil types of CIS ar
e given. A well-defined correlation is shown between the species compo
sition of microbial complexes, ecological functions of microorganisms,
and their confinement to certain soil types. Several environmental fa
ctors prove to be responsible for structure of microbial complexes, wh
ich reflects the adaptation of microorganisms to natural conditions of
soil zones. Further discussed is the succession approach, capable of
making a more complete accounting for the microbial diversity in soils
.