Radioactive Fingerprinting of Microorganisms That Oxidize Atmospheric Methane in Different Soils

• Published in: Applied and Environmental Microbiology
• Main Authors: Roslev, Peter, Iversen, Niels
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society for Microbiology 1999
• Subjects: Arctic; Greenland
• Online Access: http://dx.doi.org/10.1128/aem.65.9.4064-4070.1999; https://journals.asm.org/doi/pdf/10.1128/AEM.65.9.4064-4070.1999

ABSTRACT Microorganisms that oxidize atmospheric methane in soils were characterized by radioactive labelling with 14 CH 4 followed by analysis of radiolabelled phospholipid ester-linked fatty acids ( 14 C-PLFAs). The radioactive fingerprinting technique was used to compare active methanotrophs in soil samples from Greenland, Denmark, the United States, and Brazil. The 14 C-PLFA fingerprints indicated that closely related methanotrophic bacteria were responsible for the oxidation of atmospheric methane in the soils. Significant amounts of labelled PLFAs produced by the unknown soil methanotrophs coeluted with a group of fatty acids that included i17:0, a17:0, and 17:1ω8c (up to 9.0% of the total 14 C-PLFAs). These PLFAs are not known to be significant constituents of methanotrophic bacteria. The major PLFAs of the soil methanotrophs (73.5 to 89.0% of the total PLFAs) coeluted with 18:1 and 18:0 fatty acids (e.g., 18:1ω9, 18:1ω7, and 18:0). The 14 C-PLFAs fingerprints of the soil methanotrophs that oxidized atmospheric methane did not change after long-term methane enrichment at 170 ppm CH 4 . The 14 C-PLFA fingerprints of the soil methanotrophs were different from the PLFA profiles of type I and type II methanotrophic bacteria described previously. Some similarity at the PLFA level was observed between the unknown soil methanotrophs and the PLFA phenotype of the type II methanotrophs. Methanotrophs in Arctic, temperate, and tropical regions assimilated between 20 and 54% of the atmospheric methane that was metabolized. The lowest relative assimilation (percent) was observed for methanotrophs in agricultural soil, whereas the highest assimilation was observed for methanotrophs in rain forest soil. The results suggest that methanotrophs with relatively high carbon conversion efficiencies and very similar PLFA compositions dominate atmospheric methane metabolism in different soils. The characteristics of the methane metabolism and the 14 C-PLFA fingerprints excluded any significant role of autotrophic ammonia ...