Deciphering Microbial Metal Toxicity Responses via Random Bar Code Transposon Site Sequencing and Activity-Based...

Area of Science:

• Microbial Ecology and Environmental Microbiology
• Molecular Biology and Genomics
• Biochemistry and Metabolomics

Background:

• Facultative anaerobe Pantoea sp. strain MT58 (MT58) is an environmental isolate from metal-contaminated groundwater at Oak Ridge Reservation (ORR).
• Elevated concentrations of aluminum (Al3+), chromate (CrO42-), and uranyl (UO22+) pose environmental risks at ORR nuclear waste sites.
• Understanding microbial responses to metal stress is crucial for environmental remediation and assessing ecological impacts.

Purpose of the Study:

• To identify metal toxicity targets and defense mechanisms in Pantoea sp. strain MT58 (MT58) using a multiomic approach.
• To investigate the effects of Al3+, CrO42-, and UO22+ on MT58 under both aerobic and anaerobic conditions.
• To elucidate the synergistic roles of genes and metabolites in microbial metal tolerance.

Main Methods:

• Employed a multiomic strategy combining random barcode transposon site sequencing (RB-TnSeq) and activity-based metabolomics.
• Applied both global techniques to MT58 exposed to Al3+, CrO42-, and UO22+ under aerobic and anaerobic conditions.
• Analyzed gene essentiality and metabolic profiles to pinpoint molecular interactions and defense pathways.

Main Results:

• Al3+ toxicity was linked to intracellular arginine binding, impacting its synthesis.
• CrO42- uptake occurred via sulfate transporters, leading to oxidation of intracellular thiols.
• Membrane-bound lipopolysaccharides and the Tol outer membrane system provided protection against UO22+ and other metal toxicities, with evidence of lipid content regulation under metal stress.

Conclusions:

• The synergistic application of RB-TnSeq and activity-based metabolomics effectively identified novel metal-microbe interactions and defense mechanisms in MT58.
• MT58 exhibits specific molecular strategies to counteract the toxicity of different metals, including targeting arginine synthesis by Al3+.
• Findings enhance understanding of microbial adaptation to metal-contaminated environments and the broader ecological implications of metal pollution.