Methanosarcina lacustris sp nov., a new psychrotolerant methanogenic archaeon from anoxic lake sediments

A new psychrotolerant methanogenic archaeon strain ZS was isolated from anoxic lake sediments (Switzerland). The cells of the organism were non-motile cocci, 1.5-3.5 mum in diameter. The cells aggregated and formed pseudoparenchyma. The cell wall was Gram-positive. The organists utilized methanol, mono-, di-, trimethylamine and H-2/CO2 with methane production. The temperature range for growth was 1-35 degreesC with an optimum at 25 degreesC. The DNA G+C content of the organism was 43.4. mol%. Analysis of the 16S rRNA gene sequence showed that strain ZS was phylogenetically closely related to members of the genus Methanosarcina, but clearly differed from all described species of this genus (95.6-97.6% of sequence similarity). The level of DNA-DNA hybridization of strain ZS with Methanosarcina barkeri and Methanosarcina mazei was 15 and 31%, respectively. Based on the results of physiological and phylogenetic studies strain ZS can be assigned to a new species of the genus Methanasarcina. The name Methanosarcina lacustris sp. nov. is proposed. The type strain is ZS (= DSM 13486(T), VKM B-2268). The GenBank accession number for the sequence reported in the paper is AF 4.32127.