AUTHOR=Amin Aatif , Naveed Muhammad , Sarwar Arslan , Rasheed Sunbul , Saleem Hafiz Ghulam Murtaza , Latif Zakia , Bechthold Andreas 

TITLE=In vitro and in silico Studies Reveal Bacillus cereus AA-18 as a Potential Candidate for Bioremediation of Mercury-Contaminated Wastewater

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.847806

DOI=10.3389/fmicb.2022.847806

ISSN=1664-302X

ABSTRACT=<p>Mercury (Hg) pollution is a worldwide problem and increasing day by day due to natural and anthropogenic sources. In this study, mercury-resistant (Hg<sup>R</sup>) bacterial isolates were isolated from industrial wastewater of Ittehad Chemicals Ltd., Kala Shah Kaku, Lahore, Pakistan. Out of 65 bacterial isolates, five isolates were screened out based on showing resistance at 30–40 μg/ml against HgCl<sub>2</sub>. Selected Hg-resistant bacterial isolates were characterized as <italic>Bacillus subtilis</italic> AA-16 (OK562835), <italic>Bacillus cereus</italic> AA-18 (OK562834), <italic>Bacillus</italic> sp. AA-20 (OK562833), <italic>Bacillus paramycoides</italic> AA-30 (OK562836), and <italic>Bacillus thuringiensis</italic> AA-35 (OK562837). <italic>B. cereus</italic> AA-18 showed promising results in the resistance of HgCl<sub>2</sub> (40 μg/ml) due to the presence of <italic>mer</italic>A gene. Scanning electron microscopy (SEM) analysis of immobilized <italic>B. cereus</italic> AA-18 showed the accumulation Hg on the cell surface. The inoculation of immobilized <italic>B. cereus</italic> AA-18 remediated 86% Hg of industrial wastewater up to 72 h at large scale (<italic>p</italic> &lt; 0.05). <italic>In silico</italic> analysis showed structural determination of MerA protein encoded by <italic>mer</italic>A gene of <italic>B. cereus</italic> AA-18 (OK562598) using ProtParam, Pfam, ConSurf Server, InterPro, STRING, Jpred4, PSIPRED, I-TASSER, COACH server, TrRosetta, ERRAT, VERIFY3D, Ramachandran plot, and AutoDock Vina (PyRx 8.0). These bioinformatics tools predicted the structural-based functional homology of MerA protein (mercuric reductase) associated with <italic>mer</italic> operon harboring bacteria involved in Hg-bioremediation system.</p>