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Six copper-resistant bacterial strains were isolated from wastewater of tanneries of Kasur and Rohi Nala. Two strains tolerated copper at 380 mg/L, four up to 400 mg/L. Three strains were identified as members of the genus Salmonella; one strain was identified as Streptococcus pyrogenes, one as Vagococcus fluvialis and the last was identified as Escherichia coli. The pH and temperature optimum for two of them were 7.0 and 30 degrees C, respectively; four strains had corresponding optima at 7.5 and 37 degrees C, respectively. All bacterial isola-tes showed resistance against Ag+ (280-350 mg/L), Co2+ (200-420), CrVI (280-400), Cd2+ (250-350), Hg2+ (110-200), Mn2+ (300-380), Pb2+ (300-400), Sn2+ (480-520) and Zn2+ (300-450). Large-sized plasmids (> 20 kb), were detected in all of the strains. After the isolates were cured of plasmids with ethidium bromide, the efficiency of curing was estimated in the range of 60-90%. Reference strain of E. coli was transformed with the plasmids of the bacterial isolates which grew in Luria-Bertani medium containing 100 mg/L Cu2+. The capability to adsorb and afterwards accumulate Cu2+ inside their cells was assayed by atomic absorption spectrophotometer; all bacterial cells had the ability to adsorb 50-80% of the Cu2+ and accumulate 30-45% Cu2+ inside them after 1 d of incubation.

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This study was aimed at assessing the ability of Bacillus sp.ev3 to reduce hexavalent chromium into its trivalent form. Bacillus sp.ev3 could tolerate Cr(6+) (4800 microg/mL), Pb(2+) (800 microg/mL), Cu(2+) (200 microg/mL), Cd(2+) (50 microg/mL), Zn(2+) (400 microg/mL), Ni(2+) (4000 microg/mL) and Hg(2+) (50 microg/mL). Bacillus sp.ev3 showed optimum growth at 37 degrees C and pH at 7. Bacillus sp.ev3 could reduce 91% of chromium from the medium after 96 h and was also capable to reduce 84% chromium from the industrial effluents after 144 h. Cell free extracts of Bacillus sp.ev3 grown in the presence of Cr showed reduction of 70%, 45.6% and 27.4% at concentrations of 10 microg Cr(6+)/mL, 50 microg Cr(6+)/mL and 100 microg Cr(6+)/mL, respectively.