A distinct freshwater‐adapted subgroup of ANME‐1 dominates active archaeal communities in terrestrial subsurfaces in Japan

Abstract

Anaerobic methane-oxidizing archaea (ANME) are known to play an important role in methane flux, especially in marine sediments. The 16S rRNA genes of ANME have been detected in terrestrial freshwater subsurfaces. However, it is unclear whether ANME are actively involved in methane oxidation in these environments. To address this issue, Holocene sediments in the subsurface of the Kanto Plain in Japan were collected for biogeochemical and molecular analysis. The potential activity of the anaerobic oxidation of methane (AOM) (0.38-3.54 nmol cm⁻³ day⁻¹) was detected in sediment slurry incubation experiments with a (13) CH(4) tracer. Higher AOM activity was observed in low-salinity treatment compared with high-salinity condition (20‰), which supports the adaptation of ANME in freshwater habitats. The 16S rRNA sequence analysis clearly revealed the presence of a distinct subgroup of ANME-1, designated ANME-1a-FW. Phylogenetic analysis of the mcrA genes also implied the presence of the distinct subgroup in ANME-1. ANME-1a-FW was found to be the most dominant active group in the archaeal communities on the basis of 16S rRNA analysis (75.0-93.8% of total archaeal 16S rRNA clones). Sulfate-reducing bacteria previously known as the syntrophic bacterial partners of ANME-1 was not detected. Our results showed that ANME-1a-FW is adapted to freshwater habitats and is responsible for AOM in terrestrial freshwater subsurface environments.

Microbial and Reactive Transport Modeling Evidence for Hyporheic Flux‐Driven Cryptic Sulfur Cycling and Anaerobic Methane Oxidation in a Sulfate‐Impacted Wetland‐Stream System

“…A challenge to corroborating model predictions of AOM in the upper 10 cm of the sediment profiles with microbial analysis is the lack of pure cultures of organisms capable of mediating AOM and persisting uncertainties in AOM pathways. However, a metabolically active community of anaerobic methanotrophic (ANME) archaea has been identified in terrestrial and freshwater subsurface environments (Takeuchi et al, ; Timmers et al, ; Weber et al, , ), and recent studies have linked AOM to SO reduction for specific taxonomic groups of ANME and other AOM‐associated archaea in freshwater subsurface environments (Milucka et al, ; Timmers et al, , ; Weber et al, ). In our samples, it is possible that the archaeal community includes consortia of ANME, but unfortunately, taxonomic profiling of the OTUs could not resolve the ANME‐specific clades with the short‐read DNA sequences, and paprica analysis is limited to known pathways in pure culture isolates.…”

Reverse Methanogenesis and Respiration in Methanotrophic Archaea

“…Indications exist that AOM can be coupled to the reduction of different metal (oxides) (Table 1, reactions (3)–(5)), but limited experimental evidence exists to date that ANME are responsible for this reaction (discussed in Section 3.3). Besides marine environments, ANME involved in S-AOM can be found in terrestrial [25, 26] and freshwater ecosystems [27]. …”

Analysis of methane-producing and metabolizing archaeal and bacterial communities in sediments of the northern South China Sea and coastal Mai Po Nature Reserve revealed by PCR amplification of mcrA and pmoA genes

“…On the other hand, mcrA gene has been classified into ANME-a, b, c, d, e, and f phylotypes. Recently, two newly identified mcrA gene subgroups designated as ANME-g and ANME-h have been established, in which, group g is regarded as representatives specifically adapted to terrestrial freshwater (Takeuchi et al, 2011). Through the parallel phylogenetic comparison of 16S rRNA gene and mcrA gene, corresponding relationships have been established as follows: mcrA subgroups a-b and g-h, c-d, f to be in ANME 1, 2c, 3 subtypes, respectively, while mcrA subgroup e was postulated to be in ANME-2a (Hallam et al, 2003; Lösekann et al, 2007).…”