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Chromium (VI) contamination has accelerated due to rapid industrialization worldwide. Aim of this study is to check the bacterial species for their tolerance towards chromium (VI), chromium (VI) reduction under various pH and further check whether these bacteria are reducing Cr (VI) und er the influence of various metals, carbon source and protein denaturant. Bacterial strains were isolated from metal contaminated soils of Abeokuta. All of the isolates showed tolerance to chromium (VI). Among all the strains, only Bacillus species PB5 showed reduction of Chromium (VI). Maximum reduction (90%) of chromium (VI) was observed at pH 7 by Bacillus species PB5. Similarly, Bacillus species PB5 also reduced the chromium considerably at pH 6 (86%) and pH 8 (87.5%) at a concentration of 100 μg Cr mLG 1 after 120 h of incubation. Bacillus species PB5 also showed chromium (VI) reduction under various metals, protein denaturant and carbon source. There was maximum decrease in Cr (VI) reduction under the influence of PbCl 2 which was followed by ZnCl 2. Urea and citrate also decreased Cr (VI) reduction compared to control cells. Due to above properties strains could therefore be used as bioremediators of metals in soils contaminated with heavy metals.

Chromium (VI) contamination has accelerated due to rapid industrialization worldwide. Aim of this study is to check the bacterial species for their tolerance towards multiple metals, antibiotics and plant growth promoting activity and further check whether these bacteria are reducing Cr (VI). Bacterial strains were isolated from metal contaminated soils of Abeokuta. All of the isolates showed tolerance to lead, zinc and chromium (VI). Bacterial specie also showed tolerance towards antibiotics, 100% of the isolates were tolerant to Septrin, Chloramphenicol, Sparfloxacin, Amoxicillin, Augmentin, Tarivid and Streptomycin, whereas 83.33% were tolerant to Gentamycin and Pefloxacin and 33.33% were resistant to Ciprofloxacin. All bacterial species were positive to ammonia, whereas strain PZ3 and PZ4 were found to be positive to HCN. Among all the strains, only Streptococcus spp. PZ4 showed reduction of Chromium (VI). Maximum reduction (85%) of chromium (VI) was observed at pH 7 by Streptococcus spp. PZ4. Similarly, Streptococcus spp. PZ4 reduced the chromium considerably at pH 5 (51.25%), pH 6 (72.5%), pH 8 (67.5%) and at pH 9 (45%), at a concentration of 100 µg Cr mLG after 120 h of incubation. Streptococcus spp. PZ4 1 reduced chromium (VI) at a concentration of 50 µg Cr mLG (47.5%), 100 µg Cr mLG (91.25%) and 1 1 150 µg Cr mLG (134.17%). Due to above properties strains could therefore be used a s 1 bioremediators of metals in soils contaminated with heavy metals and can also increase the yield of various crops under heavy metal contamination.

Author PAW designed and planned all the experiments and methods of the present study and also wrote this article, authors ANO, NR and OOS performed the tests under in vitro conditions, author IAW did the analytical analysis whereas author SW did statistical analysis, made the graphs as well as collected all the literature for performing the tests and for writing the paper. All the authors read and approved the final manuscript.