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.
Highlights
Ever since the first methanotroph was described a century ago by Söhngen [1], it has been known that methanotrophs are actively involved in a global cycle of methane [2]
We intended to test whether cerium (III) has an upregulating effect on methane oxidation and the mmo promoter activity of either culture
Hasownoetvneerg, tahtieveMly. saiflfveecstterdisbmymmoepthroanmool t(etrhewas only alternative substrate that M. stellata will metabolize). These findings indicate that a different much weaker in M. stellata growing on methane and was not negatively affected by methanol. These findings indicate that a different mode of sMMO gene regulation has been adopted by the facultative methanotroph Methylocella silvestris compared to the obligate methanotroph Methyloferula stellata
Summary
Ever since the first methanotroph was described a century ago by Söhngen [1], it has been known that methanotrophs are actively involved in a global cycle of methane [2]. Aerobic methanotrophs inhabit diverse ecosystems where an anoxic/oxic interfaces exist, and oxidize anaerobically produced methane using O2 as an electron acceptor. The enzyme responsible for the initial step of methane oxidation is methane monooxygenase (MMO), which exists in two evolutionarily unrelated forms: a soluble, cytoplasmic form (sMMO), and a particulate, membrane-bound form (pMMO). The Beijerinckiaceae family encompasses species with diverse phenotypes, including versatile chemoorganotrophs, phototrophs, obligate methanotrophs, facultative methylotrophs and methanotrophs [12]. The methanotrophs in this family include the only two genera known to use the sMMO enzyme exclusively to activate methane: Methylocella and Methyloferula [13,14]. All other methanotrophs possess just pMMO, or both pMMO and sMMO
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
