![Fig. 2. Characterization of growth and kinetic parameters of M. buryatense 5GB1C. (A) Relationship between specific growth rates and the methane concentrations of inlet gas. In the range between 200 ppm and 2,500 ppm methane, the yellow line represents the fitted linear regression curve (R 2 = 0.82, P = 1.2 × 10 −5 ). Growth data at 20% (v/v) or 200,000 ppm CH 4 balanced with 5% O 2 and 75% N 2 were based on a previous report (22). (B) A linear relationship between the specific growth rate and the methane uptake rate. The yellow line represents the fitted linear regression curve (R 2 = 0.96, P = 3.6 × 10 −15 ). (C) The Michaelis-Menten plot of whole-cell methane uptake rate [mmol methane (gram cell dry weight) −1 h −1 ] as a function of initial substrate concentration (R 2 = 0.96, P = 1.6 × 10 −17 ). The initial substrate concentration was calculated based on Henry's law (Methods and Materials). (D) Linear regression of the linear region of the Michaelis-Menten curve (R 2 = 0.93, P = 6.6 × 10 −8 ). Each symbol represents an independent measurement.](https://www.researchgate.net/publication/373264865/figure/fig2/AS:11431281203120296@1699209259877/Characterization-of-growth-and-kinetic-parameters-of-M-buryatense-5GB1C-A_Q320.jpg)
![Fig. 3. Transcriptional changes of M. buryatense 5GB1C grown at 500 ppm (blue) and 1,000 ppm (orange) methane in comparison to 2.5% (v/v) methane growth conditions. (A-F) Volcano plots of gene expression changes of the entire genome (A), core central carbon metabolism (B), energy metabolism (C), biosynthesis of building blocks and cofactors (D), translation and transcription apparatus (E), and motility and chemotaxis (F). Symbol sizes are correlated with gene expression as shown in the figure. The horizontal dashed line represents P = 0.05. The two vertical dashed lines represent log 2 -fold at −1 and 1, respectively. Genes that do not change significantly are colored in gray. Gene abbreviations and gene products: csp, cold shock protein; fae, formaldehyde activating enzyme; fdh, formate dehydrogenase; mtk, malate-CoA ligase; atpC, F 1 F 0 type ATP synthase subunit epsilon; atpH, F 1 F 0 type ATP synthase subunit delta; nuoF, NADH-quinone oxidoreductase subunit NuoF; fabA, 3-hydroxyacyl-[acyl-carrier-protein] dehydratase FabA; csrA, carbon storage regulator CsrA; glyA, glycogen synthase GlgA; zapA, cell division protein ZapA; rpmA, 50S ribosomal protein L27; flgA, flagellar basal body P-ring formation chaperone FlgA; flgN, flagellar protein FlgN. An interactive version of this figure is available at https://erinhwilson.github.io/limited-ch4-tpm-analysis/.](https://www.researchgate.net/publication/373264865/figure/fig3/AS:11431281203120297@1699209260212/Transcriptional-changes-of-M-buryatense-5GB1C-grown-at-500-ppm-blue-and-1-000-ppm_Q320.jpg)
August 2023
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51 Citations
Proceedings of the National Academy of Sciences
The rapid increase of the potent greenhouse gas methane in the atmosphere creates great urgency to develop and deploy technologies for methane mitigation. One approach to removing methane is to use bacteria for which methane is their carbon and energy source (methanotrophs). Such bacteria naturally convert methane to CO2 and biomass, a value-added product and a cobenefit of methane removal. Typically, methanotrophs grow best at around 5,000 to 10,000 ppm methane, but methane in the atmosphere is 1.9 ppm. Air above emission sites such as landfills, anaerobic digestor effluents, rice paddy effluents, and oil and gas wells contains elevated methane in the 500 ppm range. If such sites are targeted for methane removal, technology harnessing aerobic methanotroph metabolism has the potential to become economically and environmentally viable. The first step in developing such methane removal technology is to identify methanotrophs with enhanced ability to grow and consume methane at 500 ppm and lower. We report here that some existing methanotrophic strains grow well at 500 ppm methane, and one of them, Methylotuvimicrobium buryatense 5GB1C, consumes such low methane at enhanced rates compared to previously published values. Analyses of bioreactor-based performance and RNAseq-based transcriptomics suggest that this ability to utilize low methane is based at least in part on extremely low non-growth-associated maintenance energy and on high methane specific affinity. This bacterium is a candidate to develop technology for methane removal at emission sites. If appropriately scaled, such technology has the potential to slow global warming by 2050.