Vertical profiles of methanogenesis and methanogens in two contrasting acidic peatlands in central New York State, USA

Abstract

Northern acidic peatlands are important sources of atmospheric methane, yet the methanogens in them are poorly characterized. We examined methanogenic activities and methanogen populations at different depths in two peatlands, McLean bog (MB) and Chicago bog (CB). Both have acidic (pH 3.5-4.5) peat soils, but the pH of the deeper layers of CB is near-neutral, reflecting its previous existence as a neutral-pH fen. Acetotrophic and hydrogenotrophic methanogenesis could be stimulated in upper samples from both bogs, and phylotypes of methanogens using H2/CO2 (Methanomicrobiales) or acetate (Methanosarcinales) were identified in 16S rRNA gene clone libraries and by terminal restriction fragment length polymorphism (T-RFLP) analyses using a novel primer/restriction enzyme set that we developed. Particularly dominant in the upper layers was a clade in the Methanomicrobiales, called E2 here and the R10 or fen group elsewhere, estimated by quantitative polymerase chain reaction to be present at approximately 10(8) cells per gram of dry peat. Methanogenic activity was considerably lower in deeper samples from both bogs. The methanogen populations detected by T-RFLP in deeper portions of MB were mainly E2 and the uncultured euryarchaeal rice cluster (RC)-II group, whereas populations in the less acidic CB deep layers were considerably different, and included a Methanomicrobiales clade we call E1-E1', as well as RC-I, RC-II, marine benthic group D, and a new cluster that we call the subaqueous cluster. E2 was barely detectable in the deeper samples from CB, further evidence for the associations of most organisms in this group with acidic habitats.

Metatranscriptomic Analysis of Arctic Peat Soil Microbiota

“…5). Several studies have shown that methanogenic communities switch from hydrogenotrophic to acetoclastic methanogenesis with peat depth (43)(44)(45), while others have shown that the proportion of hydrogenotrophic methanogenesis increased with depth (46). Our results indicate that acetoclastic methanogens were both more abundant and more active in the deeper layers, while hydrogenotrophs were more abundant in the top layers.…”

Heavy-Machinery Traffic Impacts Methane Emissions as Well as Methanogen Abundance and Community Structure in Oxic Forest Soils

“…Members of the families Methanosaetaceae and Methanobacteriaceae were only rarely detected in these soils. A substantial part of the retrieved clones can be considered as colonizers of wetlands, so most of the detected methanogenic taxa were also found in peatland (7,19,26), rice fields (9), and riparian soil (27). Between 36 and 54% of the sequences formed a separate cluster within the Methanomicrobiales and showed close relationships to the Fen cluster (26).…”

“…We hypothesized that machine track formation would alter soil pore structure so as to reduce soil aeration, thereby favoring methanogens. Methanogenic archaea were characterized by PCR cloning and T-RFLP analyses of the functional mcrA gene, which encodes the subunit of methyl coenzyme M reductase, a key enzyme in methanogenesis (7,12,18,31,32,47).…”

Carbon flow from volcanic CO2 into soil microbial communities of a wetland mofette

“…Methanogens and acetogens commonly have neutral pH optima as they rely on a membrane proton gradient for energy conservation (Whitman et al,, 2001;Drake et al, 2013) and therefore must be well adapted, that is, buffered intracellularly, to survive in these environments. Their ecological importance for the flow of carbon and reductants was shown for other acidic environments (Horn et al, 2003;Cadillo-Quiroz et al, 2006;Drake et al, 2009;Hunger et al, 2011), and their Figure 6 Conceptual model of carbon flow from volcanic CO 2 to soil carbon in the mofette summarizing the observed effects of extreme CO 2 degassing on a wetland soil. Promoted CO 2 utilization and key microbial taxa are presented.…”