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Antibiotic activity is known to affect interactions among soil microbes but very little information is available on the ecology of antibiotic microbial population in soil. To understand this activity better the abilities of streptomycete isolates from prairie soil were studied.

The PCR DNA fingerprinting technique using repetitive intergenic DNA sequences is effective in determining strain identity rapidly. The PCR technique efficiently identifies unique DNA fingerprints of pathogenic and disease-suppressive streptomyces strains. The PCR DNA fingerprints of these strains using BOXA1R primers, rather than the REP1R-I and REP2 primers, are unique, stable and reproducible.

Outer leaves of broad-leaved endive plants have higher fluorescent and pectolytic epiphytic bacterial population densities than inner leaves. The frequency distribution and variability of bacterial population size are influenced by the age of the leaves. Immigration of fluorescent bacteria on new leaves is inhibited by adjacent leaves. Leaves of younger plants have higher bacterial population sizes.

Coexisting Pseudomonas syringae strains are injected into plants to determine their ability to invade and exclude the leaves. The presence of an already existing population on the leaf surface decreases the development of newly introduced challenge strains. P. syringae strains exhibit differences in their capacity to coexist, invade and exclude on the phylloplane. In 107 pairwise combinations, 29 strains are injected into plants for the examination of their ability to invade and exclude.

The article discusses the development of new techniques, which can be used for the quantification of Streptomyces scabiei and antibiotic-producing Streptomyces lavendulae strains. The assays are shown to be extremely beneficial for studying the competitive dynamics of these compounds in the complex soil communities.

Quantifying target microbial populations in complex communities remains a barrier to studying species interactions in soil environments. Quantitative PCR (qPCR) assays were developed for quantifying pathogenic Streptomyces scabiei and antibiotic-producing Streptomyces Iavendulae strains in complex soil communities. This assay will be useful for evaluating the competitive dynamics of streptomycetes in soil. [ABSTRACT FROM AUTHOR]