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

Charles W. Knapp, David A. Fowle, Ezra Kulczycki, Jennifer A. Roberts, David W. Graham

Research output: Contribution to journalArticle

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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 moncloxygenase (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 16SrRNA gene expression under progressively more stringent Cu supply conditions. When Cu was provided as CUC12, pMMO transcript levels increased significantly consistent with laboratory work. However, when Cu was provided as Cu-cloped iron oxide, pMMO transcript levels increased only when mb was also present. Finally, when Cu was provided as Cu-cloped 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.
LanguageEnglish
Pages12040-12045
Number of pages5
JournalProceedings of the National Academy of Sciences
Volume104
Issue number29
Publication statusPublished - Jul 2007

Fingerprint

gene expression
methane
copper
mineral
oxidation
geochemistry
iron oxide
global warming
mineralogy
greenhouse gas
glass

Keywords

  • methanotroph
  • bioweathering
  • methane oxidation
  • particulate methane
  • monooxygenase
  • real-time RT-PCR

Cite this

Knapp, Charles W. ; Fowle, David A. ; Kulczycki, Ezra ; Roberts, Jennifer A. ; Graham, David W. / Methane monooxygenase gene expression mediated by methanobactin in the presence of mineral copper sources. In: Proceedings of the National Academy of Sciences . 2007 ; Vol. 104, No. 29. pp. 12040-12045.
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Methane monooxygenase gene expression mediated by methanobactin in the presence of mineral copper sources. / Knapp, Charles W.; Fowle, David A.; Kulczycki, Ezra; Roberts, Jennifer A.; Graham, David W.

In: Proceedings of the National Academy of Sciences , Vol. 104, No. 29, 07.2007, p. 12040-12045.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Methane monooxygenase gene expression mediated by methanobactin in the presence of mineral copper sources

AU - Knapp, Charles W.

AU - Fowle, David A.

AU - Kulczycki, Ezra

AU - Roberts, Jennifer A.

AU - Graham, David W.

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N2 - 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 moncloxygenase (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 16SrRNA gene expression under progressively more stringent Cu supply conditions. When Cu was provided as CUC12, pMMO transcript levels increased significantly consistent with laboratory work. However, when Cu was provided as Cu-cloped iron oxide, pMMO transcript levels increased only when mb was also present. Finally, when Cu was provided as Cu-cloped 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.

AB - 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 moncloxygenase (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 16SrRNA gene expression under progressively more stringent Cu supply conditions. When Cu was provided as CUC12, pMMO transcript levels increased significantly consistent with laboratory work. However, when Cu was provided as Cu-cloped iron oxide, pMMO transcript levels increased only when mb was also present. Finally, when Cu was provided as Cu-cloped 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.

KW - methanotroph

KW - bioweathering

KW - methane oxidation

KW - particulate methane

KW - monooxygenase

KW - real-time RT-PCR

UR - http://www.pnas.org/

M3 - Article

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EP - 12045

JO - Proceedings of the National Academy of Sciences

T2 - Proceedings of the National Academy of Sciences

JF - Proceedings of the National Academy of Sciences

SN - 1091-6490

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ER -