International Journal of Environmental Sciences

The response, to different concentrations of chromium (vi), of bacterial isolates from a sewage oxidation ditch was investigated. Bacteria were isolated from sewage effluent in the oxidation ditch and chromium (vi) tolerance of the isolates determined by plating on media amended with different concentrations of the chromium. The isolates were identified as members of Staphylococcus spp., Bacillus spp., Pseudomonas spp., Micrococcus sp. and E. coli. The growth of the isolates in presence of chromium (vi) showed decrease with increasing concentrations of the metal. The inhibition was significant at chromium concentrations of 200 μ/ml and above. However, the growth of the isolates in the presence of l50 μ/ml chromium showed lag phases much longer than that in the absence of chromium. The isolates were resistant to high concentrations of chromium as they were able to grow at Cr (vi) concentration of up to 500 μ/ml (10 mM). As a result, the bacterial isolates obtained in this study were intrinsically resistant to high concentration of Cr (vi) and can be potential candidates in the cleanup of chromium-contaminated systems.