Untitled

Abstract

A methanogen, strain AK-1, was isolated from permanently cold marine sediments, 38- to 45-cm below the sediment surface at Skan Bay, Alaska. The cells were highly irregular, nonmotile coccoids (diameter, 1 to 1.2 microm), occurring singly. Cells grew by reducing CO2 with H2 or formate as electron donor. Growth on formate was much slower than that on H2. Acetate, methanol, ethanol, 1- or 2-propanol, 1- or 2-butanol and trimethylamine were not catabolized. The cells required acetate, thiamine, riboflavin, a high concentration of vitamin B12, and peptones for growth; yeast extract stimulated growth but was not required. The cells grew fastest at 25 degrees C (range 5 degrees C to 25 degrees C), at a pH of 6.0-6.6 (growth range, pH 5.5-7.5), and at a salinity of 0.25-1.25 M Na+. Cells of this and other H2-using methanogens from saline environments metabolized H2 to a very low threshold pressure (less than 1 Pa) that was dependent on the methane partial pressure. We propose that the threshold pressure may be limited by the energetics of catabolism. The sequence of the 16S rDNA gene of strain AK-1 was most similar (98%) to the sequences of Methanogenium cariaci JR-1 and Methanogeniumfrigidum Ace-2. DNA-DNA hybridization between strain AK-1 and these two strains showed only 34.9% similarity to strain JR-1 and 56.5% similarity to strain Ace-2. These analyses indicated strain AK-1 should be classified as a new species within the genus Methanogenium. Phenotypic differences between strain AK-1 and these strains (including growth temperature, salinity range, pH range, and nutrient requirements) support this. Therefore, a new species, Methanogenium marinum, is proposed with strain AK-1 as type strain.

Environmental Shaping of Sponge Associated Archaeal Communities

“…Seawater in the inner bay site contains mainly sequences affiliated with Euryarchaeota members with low identity sequences from the database, possibly representing new species. Moreover, some inner bay OTUs are related to archaea detected in anoxic environments and were similar to sequences detected in a previous study in the same bay [22] and to sequences related to methanogenic archaea [33]. Crenarchaeota are well represented and show a lower diversity in planktonic archaea from the Cagarras Archipelago.…”

An Antimethanogenic Nutritional Intervention in Early Life of Ruminants Modifies Ruminal Colonization by Archaea

“…At days 2, 4, 6, and 8 of incubation (and up to 12 days for M. mobile ), tubes were analysed for CH 4 production using a flame ionization-detection GC [23]. In brief, a subsample of 0.5 mL of gas from headspace in each tube was taken and then injected manually in the GC (HP Hewlett 5890, Packard Series II, Waldbronn, Germany) using a 1 mL SampleLock syringe (Hamilton, Nevada, USA).…”

Long-chain fatty acid feeding frequency in anaerobic codigestion impacts syntrophic community structure and biokinetics

“…In addition to lower acetate, a lower hydrogen concentration would also provide more freeenergy for growth via LCFA β-oxidation (Schink, 1997;Stams and Plugge, 2009). Lower hydrogen levels could have been promoted in the PF2 codigester, which had higher concentrations of hydrogenotrophic Methanoculleus that have higher affinities for hydrogen in comparison to Methanobacterium (Chong et al, 2002;Lovley, 1985) that were more abundant in the CF codigester. A more detailed thermodynamic analysis would be needed to elucidate how the LCFA feeding strategy impacted the fluxes of intermediate metabolites during syntrophic conversion, but such work is warranted to improve our understanding of codigester LCFA conversion kinetics and syntrophic community structure.…”