Transcriptional analysis and molecular dynamics simulations reveal the mechanism of toxic metals removal and efflux pumps in Lysinibacillus sphaericus OT4b.31

Lysinibacillus sphaericus strain OT4b.31 is a bacterium widely applied in bioremediation processes of hydrocarbon and metal polluted environments. In this study, we identified the molecular mechanism underlying the Pb2+ and Cr6+ resistance. Metal uptake and temporal transcription patterns of metal r...

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Bibliographic Details
Published in:International biodeterioration & biodegradation 2018-02, Vol.127, p.46-61
Main Authors: Shaw, Dario Rangel, Dussan, Jenny
Format: Article
Language:English
Subjects:
Aromatic compounds
Bacteria
Binding
Bioaccumulation
Bioremediation
Catalysis
Cations
Chromium
Cytoplasm
Docking
Efflux
Efflux pumps
Gene expression
Heavy metals
Imidazole
Lead
Lysinibacillus sphaericus
Metals
Molecular chains
Molecular dynamics
Mutagenesis
Operons
Polluted environments
Protein interaction
Proteins
RT-qPCR
Simulation
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Summary:Lysinibacillus sphaericus strain OT4b.31 is a bacterium widely applied in bioremediation processes of hydrocarbon and metal polluted environments. In this study, we identified the molecular mechanism underlying the Pb2+ and Cr6+ resistance. Metal uptake and temporal transcription patterns of metal resistance operons were evaluated using reverse-transcribed quantitative PCR amplification. The function of the resistance determinants was studied applying docking and in silico mutagenesis methods. The results revealed that the adaptation of Lysinibacillus sphaericus OT4b.31 to elevated levels of lead and chromium involves the pbr and chr operons which comprise a transcriptional regulatory component (pbrR and chrB) and efflux ATPases (pbrA and chrA) to expel ions from the cytoplasm. Expression of metal resistance genes was constitutive and specifically inducible to the exposure of Pb2+ and Cr6+. The simultaneous presence of cations didn't affect the bioaccumulation of metals, evidencing the multimetal resistance of L. sphaericus. Docking analysis revealed the key metal-protein interactions and the conformational changes after metal or ATP binding. Results showed that residues with aromatic rings or imidazole in the catalytic domain are crucial for metal binding and achievement of the function. To our knowledge, this is the first report of a specific mechanism for lead and chromium resistance in Lysinibacillus genus. From the findings of this study, it is possible to suggest the bacterium as a suitable candidate for rapid toxic metals bioremediation processes. [Display omitted] •The molecular mechanism of lead and chromium resistance in Lysinibacillus sphaericus OT4b.31 is elucidated.•The resistance is given by the pbr and chr operons.•Each resistance operon comprise a transcriptional regulatory component and efflux ATPases.•Expression of resistance genes was constitutive and specifically inducible to the exposure of lead and chromium.•The simultaneous presence of metals didn't affect the bioaccumulation.
ISSN:0964-8305
1879-0208
DOI:10.1016/j.ibiod.2017.11.016