Application of Enzyme Immunoassay for Detection of the Nitrogen-Fixing Bacteria of the Genus Azospirillum in Soil Suspensions

The enzyme immunoassay of soil suspensions was performed using antibodies against the lipopolysaccharides of Azospirillum brasilense model strains in order to assess the monthly population dynamics of the A. brasilense Sp245 introduced into the soil samples in laboratory simulation experiments and to determine the abundance of azospirilla in the various soils of the Saratov oblast. In laboratory simulation experiments (a sample of southern chernozem was used), the maximum amount of the antigen in question was detected in soil suspensions on day 7 of the one-month experiment on the introduction of bacterial cells into soil samples. Analysis of the major soil types of the Saratov oblast (saline, alluvial, and grey forest soils, as well as typical and southern chernozem) revealed the predominance of azospirilla antigens of the Sp245 serotype; significant amounts of the serotype Sp7 antigens were detected in southern chernozem.