Effect of heavy metals on the growth of Bacillus spp. isolates

The objective of this study was to investigate the effects of different concentrations of heavy metals,: namely Cobalt (Co), Cadmium (Cd), manganese (Mn), Copper (Cu), Mercury (Hg), Iron (F)e, Zinc (Zn), and Lead (Pb), on four different species of Bacillus (Bacillus subitils sub sp. subitilus, B. atrophaeus, B. mycoides, B. weihenstephananensis). Various metal concentrations (75, 125, 250, 500, and 750 µg ml-1) of each heavy metal salt were prepared and tested against the target organisms. This study showed that Bacillus spp. exhibited different responses to the different concentrations of heavy metals. Among the tested strains, B. atrophaeus and B. subtilils sub sp. subitils were the most sensitive to varying concentrations of the studied heavy metals. Cd was the most effective heavy metal on all tested strains, whereas all isolates were resistant to all concentrations of Mn and Pb. Most of the strains were resistant to different concentrations of Cu and Fe.