Impact of copper on the physiology and transcriptome of Methylosinus trichosporium OB3b grown on either methane or methanol
This study investigates the combined effects of copper availability and carbon source (methane versus methanol) on the physiology and transcriptome of Methylosinus trichosporium OB3b, a model Type II methanotroph. Methanotrophs oxidize methane to carbon dioxide through intermediates such as methanol, formaldehyde, and formate, using two forms of methane monooxygenase (MMO): the copper-dependent particulate MMO (pMMO) and the soluble MMO (sMMO). Although Msn. trichosporium OB3b can utilize both methane and methanol as sole carbon sources, growth on methanol is significantly affected by copper. In the presence of copper, methanol-grown cells exhibited impaired growth, formate accumulation, and decreased pH, while buffering with MOPS restored growth. NADH/NAD ratios increased nearly tenfold in methanol-grown cultures with copper, indicating redox imbalance. Transmission electron microscopy revealed disrupted intracytoplasmic membranes under these conditions. Transcriptomic analysis showed that genes involved in methanol oxidation were differentially expressed in response to copper and carbon source, and two siderophore biosynthetic gene clusters were repressed during methanol growth with copper. Overall, the findings suggest that Msn. trichosporium OB3b modulates metallophore expression and carbon metabolism to manage oxidative and redox stress under methanol growth conditions. Understanding these regulatory mechanisms is critical for optimizing methanotroph-based biotechnological applications, including methanol-driven biosynthesis of valuable compounds such as methanobactin. Overall design: RNA-seq profiling of Methylosinus trichosporium OB3b grown on methane with and without copper, and grown on methanol without copper and with copper plus MOPS buffer.