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

• Published in: Applied and environmental microbiology Vol. 87; no. 21; p. e0103721
• Main Authors: Thorgersen, Michael P, Xue, Jingchuan, Majumder, Erica L W, Trotter, Valentine V, Ge, Xiaoxuan, Poole, 2nd, Farris L, Owens, Trenton K, Lui, Lauren M, Nielsen, Torben N, Arkin, Adam P, Deutschbauer, Adam M, Siuzdak, Gary, Adams, Michael W W
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 14-10-2021
• Subjects: Aluminum; Anaerobic conditions; Bar codes; DNA Transposable Elements; Environmental Microbiology; Environmental Pollutants - toxicity; Groundwater; Intracellular; Lipids; Lipopolysaccharides; Membranes; Metabolites; Metabolomics; Metal concentrations; Metals; Metals - toxicity; Microorganisms; Pantoea - drug effects; Pantoea - metabolism; Radioactive wastes; Thiols; Toxicity; Transposons; metabolomics; metal resistance; transposon mutagenesis
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.01037-21

To uncover metal toxicity targets and defense mechanisms of the facultative anaerobe
sp. strain MT58 (MT58), we used a multiomic strategy combining two global techniques, random bar code transposon site sequencing (RB-TnSeq) and activity-based metabolomics. MT58 is a metal-tolerant Oak Ridge Reservation (ORR) environmental isolate that was enriched in the presence of metals at concentrations measured in contaminated groundwater at an ORR nuclear waste site. The effects of three chemically different metals found at elevated concentrations in the ORR contaminated environment were investigated: the cation Al
, the oxyanion CrO
, and the oxycation UO
. Both global techniques were applied using all three metals under both aerobic and anaerobic conditions to elucidate metal interactions mediated through the activity of metabolites and key genes/proteins. These revealed that Al
binds intracellular arginine, CrO
enters the cell through sulfate transporters and oxidizes intracellular reduced thiols, and membrane-bound lipopolysaccharides protect the cell from UO
toxicity. In addition, the Tol outer membrane system contributed to the protection of cellular integrity from the toxic effects of all three metals. Likewise, we found evidence of regulation of lipid content in membranes under metal stress. Individually, RB-TnSeq and metabolomics are powerful tools to explore the impact various stresses have on biological systems. Here, we show that together they can be used synergistically to identify the molecular actors and mechanisms of these pertubations to an organism, furthering our understanding of how living systems interact with their environment.
Studying microbial interactions with their environment can lead to a deeper understanding of biological molecular mechanisms. In this study, two global techniques, RB-TnSeq and activity metabolomics, were successfully used to probe the interactions between a metal-resistant microorganism,
sp. strain MT58, and metals contaminating a site where the organism can be located. A number of novel metal-microbe interactions were uncovered, including Al
toxicity targeting arginine synthesis, which could lead to a deeper understanding of the impact Al
contamination has on microbial communities as well as its impact on higher-level organisms, including plants for whom Al
contamination is an issue. Using multiomic approaches like the one described here is a way to further our understanding of microbial interactions and their impacts on the environment overall.