Selective effect of antibiotics on survival and gene transfer of streptomycetes in soil

Streptomycetes are prolific producers of antibiotics although there are few reports of antibiotic production in their native soil habitat. Antibiotic producers contain resistance genes within the biosynthetic gene cluster to avoid autoinhibition. Davies (1992) suggested that pathogenic bacteria acquired resistance genes from such sources. In the Netherlands, 30000 kg of neomycin and kanamycin are released annually into agricultural soils in cattle manure, although there is no information on their availability as selective agents on bacterial populations in situ. Our aim was to determine the selective effects of two antibiotics, neomycin, which binds strongly to soil clay and thiostrepton, which does not, on survival and gene transfer between streptomycetes in soil.