Chromate tolerant bacteria isolated from tannery effluent

The occurrence of metal tolerant and antibiotic resistant organisms was inv estigated in tannery effluent. Seventy-seven isolates comprising heterotrop hs (41) and coliforms (36) which were tolerant to chromate level of > 50 mu g/ml were selected for detailed study. The majority of the coliforms were r esistant to higher levels of chromate (200 mug/ml) whereas around 3% of the heterotrophs were resistant to Cr6+ at a level of > 150 mug/ml. All chroma te tolerant heterotrophs were also tolerant to Cu2+ (100%) whereas only 58. 53% coliforms were tolerant to Cu2+. Except in the case of Cd2+ a higher nu mber of heterotrophs were found tolerant to other heavy metals tested. Both groups of isolates were found sensitive to mercury. Resistance to cephalor idine was more abundant (P < 0.001) in coliforms as compared to heterotroph s. On the other hand a significantly higher number (P < 0.01) of heterotrop hs showed resistance to streptomycin and carbencillin. All coliforms were s ensitive to chloramphenicol. Around 80% and 31.70% of coliforms and heterot rophs exhibited a relationship to the combination of metals and antibiotics . Both heterotrophs and coliforms tolerant to Hg2+ were also resistant to p olymixin-B. (C) 2001 Elsevier Science Ltd. All rights reserved.