Isolation and Characterization of Methanomethylovorans hollandica gen. nov., sp. nov., Isolated from Freshwater Sediment, a Methylotrophic Methanogen Able To Grow on Dimethyl Sulfide and Methanethiol

Abstract

A newly isolated methanogen, strain DMS1T, is the first obligately anaerobic archaeon which was directly enriched and isolated from a freshwater sediment in defined minimal medium containing dimethyl sulfide (DMS) as the sole carbon and energy source. The use of a chemostat with a continuous DMS-containing gas stream as a method of enrichment, followed by cultivation in deep agar tubes, resulted in a pure culture. Since the only substrates utilized by strain DMS1T are methanol, methylamines, methanethiol (MT), and DMS, this organism is considered an obligately methylotrophic methanogen like most other DMS-degrading methanogens. Strain DMS1T differs from all other DMS-degrading methanogens, since it was isolated from a freshwater pond and requires NaCl concentrations (0 to 0.04 M) typical of the NaCl concentrations required by freshwater microorganisms for growth. DMS was degraded effectively only in a chemostat culture in the presence of low hydrogen sulfide and MT concentrations. Addition of MT or sulfide to the chemostat significantly decreased degradation of DMS. Transient accumulation of DMS in MT-amended cultures indicated that transfer of the first methyl group during DMS degradation is a reversible process. On the basis of its low level of homology with the most closely related methanogen, Methanococcoides burtonii (94.5%), its position on the phylogenetic tree, its morphology (which is different from that of members of the genera Methanolobus,Methanococcoides, and Methanohalophilus), and its salt tolerance and optimum (which are characteristic of freshwater bacteria), we propose that strain DMS1T is a representative of a novel genus. This isolate was named Methanomethylovorans hollandica. Analysis of DMS-amended sediment slurries with a fluorescence microscope revealed the presence of methanogens which were morphologically identical to M. hollandica, as described in this study. Considering its physiological properties, M. hollandica DMS1T is probably responsible for degradation of MT and DMS in freshwater sediments in situ. Due to the reversibility of the DMS conversion, methanogens like strain DMS1T can also be involved in the formation of DMS through methylation of MT. This phenomenon, which previously has been shown to occur in sediment slurries of freshwater origin, might affect the steady-state concentrations and, consequently, the total flux of DMS and MT in these systems.

Structure and function of the microbial community in an in situ reactor to treat an acidic mine pit lake

“…The type strain Methanomethylovorans hollandica converts dimethyl sulfide to CH 4 , CO 2 and H 2 S and thus tolerates high H 2 S concentrations. The coccoid cells are growing in large cell clusters (Lomans et al, 1999) very similar to the methanogens in our CLSM images (Fig. 1d).…”

Anaerobic oxidation of dimethylsulfide and methanethiol in mangrove sediments is dominated by sulfate-reducing bacteria

“…Starting from methanethiol as a substrate, conversion rates were considerably lower and comparison of the results for methanethiol with those for dimethylsulfide suggests that these compounds are in a thermodynamic equilibrium favoring methanethiol. Although interconversions of dimethylsulfide and methanethiol are generally observed (Kiene et al, 1986;Kiene, 1988;Kiene & Capone, 1988;Lomans et al, 1997Lomans et al, , 1999aLyimo et al, 2000) in sediments and ascribed to SRB and methanogenic archaea, this has not been analyzed quantitatively. Relatively large abiotic losses were observed especially during the first day and hamper interpretations (Kiene et al, 1986;Kiene & Capone, 1988).…”

Spatial distribution of microbial communities in the shallow submarine alkaline hydrothermal field of the Prony Bay, New Caledonia

“…The majority of BdJ and ST07 archaeal sequences (94-96%) were closely affiliated with the uncultured LCMS (Schrenk et al, 2004) (96-97% identity) ( Fig. 5), as related to ANME-3 and more distantly related to the Methanomethylovorans hollandica (91% identity), which can use methylamines for methanogenesis (Lomans et al, 1999).…”