title: Chromium-resistant soil actinomycetes: their tolerance to other metals and antibiotics.
abstract: Chromium occurs widely in most soils, but generally in trace amounts. Actinomycetes, one of the important components of the microbial population in soils interact with a variety of metals including chromium. This study was aimed to evaluate the tolerance of soil actinomycetes to Cr6+, other metals and antibiotics. Thirty-two actinomycete isolates were screened for their tolerance to Cr6+ on tryptone yeast extract agar medium supplemented with Cr6+ at concentrations ranging from 100 to 2000 micrograms ml-1. Thirteen Cr-tolerant isolates were selected on the basis of their growth at the highest concentration, but their performance was not satisfactory in Cr6+ containing liquid salts medium. Resistance of these isolates to other metals and antibiotics was assessed using agar-cup assay and disc diffusion technique, respectively. The sequence of metal toxicity for the actinomycete isolates was in the order Hg2+ > Ni2+ > Cu2+ > Co2+ > Cd2+, but the Cr6+ resistance of the isolates could not be correlated with their antibiotic-resistance profile.
mesh_terms: D000192:Actinomycetales / Q000187:drug effects* / Q000254:growth & development; D002857:Chromium / Q000494:pharmacology*; D003470:Culture Media / Q000737:chemistry; D004352:Drug Resistance, Microbial; D019216:Metals, Heavy / Q000494:pharmacology; D012988:Soil Microbiology