Distribution of streptomycin resistance and biosynthesis genes in streptomycetes recovered from different soil sites

Abstract

Streptomycin resistant streptomycetes were isolated from four diversesites. Two sites in Germany were sampled and included an agriculturalexperimental plot of apple trees which had a history of streptomycinapplication (AR) and a control site without antibiotic application (CR).Two sites in the UK were sampled; a pastureland site which had sewageinjection (DW) and an agricultural site (CW). The actinomycete countsindicated a high proportion of streptomycin resistant isolates in the CWsoil. Streptomycetes were identified by partial sequencing of the 16SrDNA. PCR product of the hypervariable gamma region of 16S rDNA allowedanalysis by denaturing gradient gel electrophoresis to assess thediversity within the isolates. The streptomycin and sewage sludgetreated sites showed decreased diversity within streptomycetepopulations. Isolates were screened for the streptomycin resistancegene, strA, and flanking biosynthesis gene, strB1. Distribution of thesegenes indicated the prevalence of str genes in the streptomycin treatedsoil. Evidence of horizontal gene transfer was recorded in isolatesidentified as Streptomyces platensis recovered from CR and AR siteswhich had acquired a streptomycin resistance gene homologous to thatfound in Streptomyces griseus. Members of the latter species were themost abundant streptomycin resistant streptomycetes isolated from allsoils. (C) 2002 Federation of European Microbiological Societies.Published by Elsevier Science B.V. All rights reserved.