Abstract
AbstractLakes and ponds are considered as a major natural source of CH4emissions, particularly during the ice-free period in boreal ecosystems. Aerobic methane-oxidizing bacteria (MOB), which utilize CH4using oxygen as an electron acceptor, are one of the dominant microorganisms in the CH4-rich water columns. Metagenome-assembled genomes (MAGs) have revealed the genetic potential of MOB from boreal aquatic ecosystems for various microaerobic/anaerobic metabolic functions. However, experimental proof of these functions, i.e., organic acid production via fermentation, by lake MOB is lacking. In addition, psychrophilic (i.e., cold-loving) MOB and their CH4-oxidizing process have rarely been investigated. In this study, we isolated, provided a taxonomic description, and analyzed the genome ofMethylobactersp. S3L5C, a psychrophilic MOB, from a boreal lake in Finland. Based on phylogenomic comparisons to MAGs,Methylobactersp. S3L5C represented a ubiquitous cluster ofMethylobacterspp. in boreal aquatic ecosystems. At optimal temperatures (3–12 °C) and pH (6.8–8.3), the specific growth rates (µ) and CH4utilization rate were in the range of 0.018–0.022 h−1and 0.66–1.52 mmol l−1 d−1, respectively. In batch cultivation, the isolate could produce organic acids, and the concentrations were elevated after replenishing CH4and air into the headspace. Up to 4.1 mM acetate, 0.02 mM malate, and 0.07 mM propionate were observed at the end of the test under optimal operational conditions. The results herein highlight the key role ofMethylobacterspp. in regulating CH4emissions and their potential to provide CH4-derived organic carbon compounds to surrounding heterotrophic microorganisms in cold ecosystems.
Publisher
Springer Science and Business Media LLC
Cited by
10 articles.
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