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Methane monooxygenase gene expression mediated by methanobactin in the presence of mineral copper sources.

Abstract：

:Methane is a major greenhouse gas linked to global warming; however, patterns of in situ methane oxidation by methane-oxidizing bacteria (methanotrophs), nature's main biological mechanism for methane suppression, are often inconsistent with laboratory predictions. For example, one would expect a strong relationship between methanotroph ecology and Cu level because methanotrophs require Cu to sustain particulate methane monooxygenase (pMMO), the most efficient enzyme for methane oxidation. However, no correlation has been observed in nature, which is surprising because methane monooxygenase (MMO) gene expression has been unequivocally linked to Cu availability. Here we provide a fundamental explanation for this lack of correlation. We propose that MMO expression in nature is largely controlled by solid-phase Cu geochemistry and the relative ability of Cu acquisition systems in methanotrophs, such as methanobactins (mb), to obtain Cu from mineral sources. To test this hypothesis, RT-PCR expression assays were developed for Methylosinus trichosporium OB3b (which produces mb) to quantify pMMO, soluble MMO (the alternate MMO expressed when Cu is "unavailable"), and 16S-rRNA gene expression under progressively more stringent Cu supply conditions. When Cu was provided as CuCl(2), pMMO transcript levels increased significantly consistent with laboratory work. However, when Cu was provided as Cu-doped iron oxide, pMMO transcript levels increased only when mb was also present. Finally, when Cu was provided as Cu-doped borosilicate glass, pMMO transcription patterns varied depending on the ambient mb:Cu supply ratio. Cu geochemistry clearly influences MMO expression in terrestrial systems, and, as such, local Cu mineralogy might provide an explanation for methane oxidation patterns in the natural environment.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Knapp CW,Fowle DA,Kulczycki E,Roberts JA,Graham DW

doi

10.1073/pnas.0702879104

subject

Has Abstract

pub_date

2007-07-17 00:00:00

pages

12040-5

issue

eissn

0027-8424

issn

1091-6490

pii

0702879104

journal_volume

104

pub_type

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Methane monooxygenase gene expression mediated by methanobactin in the presence of mineral copper sources.