Substantial high‐affinity methanotroph populations in Andisols effect high rates of atmospheric methane oxidation

Abstract

Methanotrophic bacteria in soils derived from volcanic ash (Andisols) were characterized via time series (13) C-phospholipid fatty acid (PLFA) labelling. Three Andisols were incubated under 2 ppmv (13) CH4 for up to 18 weeks, thus enabling high-affinity methanotrophs to be selectively characterized and quantified. PLFA profiles from all soils were broadly similar, but the magnitude of the high-affinity methanotrophic populations determined through (13) C-PLFA-stable isotope probing displayed sizeable differences. Substantial incorporation of (13) C indicated very large high-affinity methanotrophic populations in two of the soils. Such high values are far in excess (10×) of those observed for a range of mineral soils incubated under similar conditions (Bull et al., 2000; Maxfield et al., 2006; 2008a, b). Two of the three Andisols studied also displayed high but variable CH4 oxidation rates ranging from 0.03 to 1.58 nmol CH4 g(-1) d.wt. h(-1) . These findings suggest that Andisols, a previously unstudied soil class with respect to high-affinity methanotrophic bacteria, may oxidize significant amounts of atmospheric methane despite their low areal coverage globally.

Unravelling the Identity, Metabolic Potential and Global Biogeography of the Atmospheric Methane‐Oxidizing Upland Soil Cluster α

“…In some of the cave population datasets (e.g., from Portugal), the USCα sequences even exhibited a considerably higher relative abundance of up to 10% of the total microbial community, indicating not only the presence but also potential key role of USCα in these environments. There have been very few indications for the presence of atmospheric methane oxidation, for example, in volcanic soil environments on Hawaii and andisols on Tenerife (King and Nanba, ; Maxfield et al ., ), and it was so far postulated that the atmospheric methanotrophs are dependent on vegetated ecosystems with significant soil accumulation (King and Nanba, ) (hence the name ‘upland soil’ cluster). The unexpected presence of USCα 16S rRNA gene sequences in datasets from cave wall biofilms and subterranean ecosystems around the world (Hawaii‐USA, Azores/Portugal, Tenerife/Spain, USA, Venezuela, Mexico, China, Iceland, Korea, Slovenia, Bosnia and Herzegovina) show that this might not be accurate, further supported by the presence of biofilm‐related capacities in the USCα draft genome.…”

Copper Biogeochemistry: A Cornerstone in Aerobic Methanotrophic Bacterial Ecology and Activity?

“…h −1 (Maxfield et al 2009). What are the spatial factors controlling this variable methane oxidation rates?…”

The microbial methane cycle

“…Molecular‐based studies clearly show the presence of a number of pmoA genes representing these high‐affinity methanotrophs in forest and upland soils and recently important work by Liesack and colleagues (Baani and Liesack, 2008) demonstrated that Methylocystis strain SC2 has an alternative pMMO system that oxidizes methane at very low concentrations, hinting at the likely identity of this high‐affinity group. In this volume, Maxfield and colleagues (2009) describe the use of 13 CH 4 labelling of PLFAs of high‐affinity methanotrophs in soils derived from volcanic ash (Andisols) and show that these soils, which have not been examined before, are very active in oxidizing atmospheric concentrations of methane. A mini‐review by Kolb (2009) draws together all of the current information on the quest for atmospheric methane oxidizers in forest soils and suggests future directions that research needs to take in order to fully understand this very important process.…”