Analysis of Chromium Biotransformation by Indigenous Bacteria Isolated from Industrially Contaminated Sites
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Date
2024-12-05
Authors
IQRA ARSHAD
Journal Title
Journal ISSN
Volume Title
Publisher
UMT, Lhr
Abstract
Contamination of Chromium is a global environmental problem and particularly pronounced in industrial areas where the increased pollution levels of hexavalent chromium Cr(VI) pose substantial risk to human health and ecosystems. This research investigates the bioremediation potential of indigenous chromium resistant microbes obtained from an industrially polluted site at Kasur. Seven bacterial strains were isolated and characterized for their chromium-reduction capacities, with HIC1 and HIC5 recognized as the best strains in detoxifying Cr(VI) to less harmful trivalent chromium [Cr(III)]. The optimized growth conditions, including pH and temperature, were determined to improve Cr-biotransformation ability. The bacterial strains were also evaluated for phosphate solubilization, nitrogen fixation, and zinc solubilization capacities highlighting potential plant growth promotion. The results show that HIC1 showed the highest activities, including high Cr(VI) reduction. Seven chromium resistant strains were isolated with the strain that has been rated best in chromium biotransformation as well as performing nitrogen fixation, auxin production and plant
growth under stress being Staphylococcus saprophyticus HIC1. The MIC study demonstrated a variation of resistance among the bacterial isolates. HIC1 and HIC2
were sensitive to 4.5 mM of chromium, 15 mM of arsenate and 5 mM of mercuric chloride. HIC3, HIC4 and HIC5 were sensitive to 3.5 mM of chromium and 20 mM
of arsenate. HIC6 and HIC7 Were sensitive to 4.0 mM of chromium and 10 mM of arsenate while all the isolates were sensitive to 5 mM of mercuric chloride. In the Cr
biotransformation assay, the HIC1 isolate is the one with the strongest Cr(VI) reduction, with HIC3 and HIC5 performing well, followed by HIC4 and HIC7 performing moderately, and HIC6 and HIC2 poorly or not at all. HIC2-HIC7 were able to reduce mercury HIC5 was the most effective for arsenic biotransformation. Their classification at a molecular level was substantiated through PCR with HIC5 showing the most intense DNA bands. No zinc solubilization and ammonification was
found; however, moderate amounts of phosphate solubilization by HIC1 and HIC5 was noted, this indicates their usefulness in bioremediation and enhancing plant
growth. HIC1 grows shoots and roots actively, and under chromium stress, HIC3 is beneficial for growth of plants in contaminated environment. The combination of HIC1 or HIC3 with ferns was found the most effective for growth of the plants though the plants were affected by chromium. Phylogenetic analysis and 16S RNA sequencing identified the isolate HIC1 as Staphylococcus saprophyticus The study concludes that these microorganisms present in the local populations might play an important role in the development of inexpensive bioremediation technologies.