methane (CH4) is a potent greenhouse gas with a global warming potential of 28-34 times that of carbon dioxide on a centennial time scale. microbial CH4 Oxidation acts as a biofilter, blocking more than 90% of CH4 from entering the atmosphere.
Traditionally, aerobic CH4Oxidizing bacteria (MOB) is O2growth dependent on CH4 as the only source of carbon and energy. Mounting studies have shown that MOB is present and even active in low-oxygen environments, without O2 as an electron acceptor by them, but their survival strategy and ecological contribution remains obscure.
Researchers led by Dr Li Biao of Professor Wu Qinglong’s team at the Nanjing Institute of Geography and Lakes of the Chinese Academy of Sciences (NIGLAS), together with their collaborators, investigated survival strategies in MOB under hypoxic conditions. Their results have been published in water research.
After two years of enrichment, the researchers obtained an enriched consortium dominated by γ-MOB, Methylomonas, and several heterotrophic bacteria, but without the anaerobic methanotrophs.
They found that the MOB consortium could couple CH4 Oxidation and reduction of iron (III) under hypoxia using electron shuttles such as riboflavin. Within the MOB consortium, MOB transferred CH4 to low molecular weight organic substances such as acetate to union bacteria as a carbon source, while the latter secretes riboflavin to facilitate extracellular electron transfer.
A metabolic flexibility was observed in this traditionally considered O2– Independent Microbe, MOB. Given that iron is the fourth most abundant element on Earth and generally abundant in lacustrine deposits, the use of iron oxides as electron acceptors may be a critical MOB and CH lifestyle of interest.4 It sinks into the early Earth, where anoxic conditions existed everywhere,” said Dr. Lee.
In the hypoxic sediments of the site, several species of consortia-associated microbes, including Methylomonas, were relatively active. In addition, the reduction of Fe(III) coupled to CH4 The MOB conjugate-mediated oxidation reduced 40.3% of CH4 Emissions in iron-rich sediments.
“There are many iron-rich regions in southern China, and MOB in these iron-rich regions may play a critical role in mitigating CH.4 Emission even under hypoxia there. Our study reveals how MOBs survive under hypoxia and expands knowledge of this previously overlooked CH4 “You drown in iron-rich sediment,” Dr. Lee said.
Biao Li et al, iron oxides act as surrogate electron acceptors for aerobic methanotrophs in anoxic lake sediments, water research (2023). DOI: 10.1016/j.waters.2023.119833
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