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Gu, W.* ; Farhan Ul Haque, M.* ; Baral, B.S.* ; Turpin, E.A.* ; Bandow, N.L.* ; Kremmer, E. ; Flatley, A. ; Zischka, H. ; DiSpirito, A.A.* ; Semrau, J.D.*

A TonB-dependent transporter is responsible for methanobactin uptake by Methylosinus trichosporium OB3b.

Appl. Environ. Microbiol. 82, 1917-1923 (2016)
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Methanobactin, a small modified polypeptide synthesized by methanotrophs for copper uptake, has been found to be chromosomally encoded. The gene encoding for the polypeptide precursor of methanobactin, mbnA, is part of a gene cluster that also includes several genes encoding for proteins of unknown function (but speculated to be involved in methanobactin formation), as well as mbnT, encoding for a TonB-dependent transporter hypothesized to be responsible for methanobactin uptake. To determine if mbnT was truly responsible for methanobactin uptake, a knock-out was constructed in Methylosinus trichosporium OB3b using marker exchange mutagenesis. The resulting M. trichosporium mbnT::Gm(R) mutant was found to be able to produce methanobactin, but unable to internalize it. Further, if this mutant was grown in the presence of copper and exogenous methanobactin, copper uptake was significantly reduced. Expression of mmoX and pmoA, encoding for polypeptides of the soluble methane monooxygenase (sMMO) and particulate methane monooxygenase (pMMO), respectively, also changed significantly when methanobactin was added, indicating that the mutant was unable to collect copper under these conditions. Copper uptake and gene expression, however, was not affected in M. trichosporium OB3b wildtype, indicating that the TonB-dependent transporter encoded by mbnT is responsible for methanobactin uptake, and that methanobactin is a key mechanism used by methanotrophs for copper uptake. When the mbnT::Gm(R) mutant was grown under a range of copper concentrations in the absence of methanobactin, however, the phenotype of the mutant was indistinguishable from M. trichosporium OB3b wildtype, indicating that this methanotroph has multiple mechanisms for copper uptake.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Methylococcus-capsulatus Bath; Particulate Methane Monooxygenase; Oxidizing Bacteria; Methanotrophic Bacteria; Anaerobic Oxidation; Escherichia-coli; Sigma-factors; Copper; Binding; Degradation
ISSN (print) / ISBN 0099-2240
e-ISSN 1098-5336
Quellenangaben Volume: 82, Issue: 6, Pages: 1917-1923 Article Number: , Supplement: ,
Publisher American Society for Microbiology (ASM)
Publishing Place Washington
Reviewing status Peer reviewed