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Differential Transcriptional Activation of Genes Encoding Soluble Methane Monooxygenase in a Facultative Versus an Obligate Methanotroph

Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
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Microorganisms 2018, 6(1), 20; https://doi.org/10.3390/microorganisms6010020
Received: 8 February 2018 / Revised: 28 February 2018 / Accepted: 1 March 2018 / Published: 6 March 2018
(This article belongs to the Section Environmental Microbiology)
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Abstract

Methanotrophs are a specialized group of bacteria that can utilize methane (CH4) as a sole energy source. A key enzyme responsible for methane oxidation is methane monooxygenase (MMO), of either a soluble, cytoplasmic type (sMMO), or a particulate, membrane-bound type (pMMO). Methylocella silvestris BL2 and Methyloferula stellata AR4 are closely related methanotroph species that oxidize methane via sMMO only. However, Methyloferula stellata is an obligate methanotroph, while Methylocella silvestris is a facultative methanotroph able to grow on several multicarbon substrates in addition to methane. We constructed transcriptional fusions of the mmo promoters of Methyloferula stellata and Methylocella silvestris to a promoterless gfp in order to compare their transcriptional regulation in response to different growth substrates, in the genetic background of both organisms. The following patterns were observed: (1) The mmo promoter of the facultative methanotroph Methylocella silvestris was either transcriptionally downregulated or repressed by any growth substrate other than methane in the genetic background of Methylocella silvetris; (2) Growth on methane alone upregulated the mmo promoter of Methylocella silvetris in its native background but not in the obligate methanotroph Methyloferula stellata; (3) The mmo promoter of Methyloferula stellata was constitutive in both organisms regardless of the growth substrate, but with much lower promoter activity than the mmo promoter of Methylocella silvetris. These results support a conclusion that a different mode of transcriptional regulation of sMMO contributes to the facultative lifestyle of Methylocella silvetris compared to the obligate methanotroph Methyloferula stellata. View Full-Text
Keywords: transcriptional regulation; methane oxidation; facultative methanotroph; obligate methanotroph; Methylocella transcriptional regulation; methane oxidation; facultative methanotroph; obligate methanotroph; Methylocella
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Smirnova, A.V.; Dunfield, P.F. Differential Transcriptional Activation of Genes Encoding Soluble Methane Monooxygenase in a Facultative Versus an Obligate Methanotroph. Microorganisms 2018, 6, 20.

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