Increasing environmental pollutants such as heavy metals have
become one of the most severe health dangers because of rapid
industrialization. Exposure to lead and nickel heavy toxic metals can
lead to hazardous diseases affecting most of the organs in humans.
Bioremediation is a process that uses the ability of microorganisms or
plants to detoxify environmental contaminants at lower costs than
physicochemical techniques. This study isolated halophilic bacteria from
Khara salt lake in Iran and screened their ability to resist lead and
nickel. After screening stages, three selected strains including
Bacillus sp. A21, Oceanobacillus sp. A22 and Salinicoccus A43 were
identified by16S rDNA sequencing and the related sequences were
submitted to GeneBank with accession IDs MN588312, MN588313, and MN
588,314, respectively. These strains resist 7.2 mM, 4.1 mM, and 6.7 mM
lead and 3.6 mM, 3.7 mM, and 4.1 mM nickel, respectively. Investigation
of growth pattern and evaluation of bioremediation ability by atomic
absorption spectroscopy revealed that Bacillus sp. A21 could decrease
lead and nickel in culture medium up to 97.5% and 76%, respectively.
Oceanobacillus sp. A22 showed higher lead bioremediation rate (98.8%)
and lower nickel-bioremediation rate (73.5%). Salinicoccus sp. A43
showed the least bioremediation ability (92% lead and 71.7% nickel). The
ability of selected strains to synthesize lead and nickel nanoparticles
was evaluated using UV/Vis spectrophotometry and Energy-Dispersive
X-ray Spectroscopy (EDX). Particle dimensions were measured using
Scanning Electron Microscopy (SEM). Bacillus sp. A21 and Oceanobacillus
sp. A22 strains were able to synthesize lead nanoparticles; however,
Salinicoccus sp. A43 could synthesize both lead and nickel
nanoparticles.