Mariniplasma anaerobium gen. nov., sp. nov., a novel anaerobic marine mollicute, and proposal of three novel genera to reclassify members of Acholeplasma clusters II-IV

A novel strictly anaerobic chemoorganotrophic bacterium, designated Mahy22(T), was isolated from sulfidic bottom water of a shallow brackish meromictic lake in Japan. Cells of the strain were Gram-stain-negative, non-motile and coccoid in shape with diameters of about 600-800 nm. The temperature range for growth was 15-37 degrees C, with optimum growth at 30-32 degrees C. The pH range for growth was pH 6.2-8.9, with optimum growth at pH 7.2-7.4. The strain grew with NaCl concentrations of 5% or below (optimum, 2-3%). Growth of the strain was enhanced by the addition of thiosulfate. The major cellular fatty acids were C-16:0 and anteiso-C-15:0. Respiratory quinones were not detected. The complete genome sequence of strain Mahy22(T) possessed a 1885846 bp circular chromosome and a 12782 bp circular genetic element. The G+C content of the genome sequence was 30.1 mol%. Phylogenetic analysis based on the 16S rRNA gene revealed that the novel strain belonged to the family Acholeplasmataceae, class Mollicutes. The closest relative of strain Mahy22(T) with a validly published name was Acholeplasma palmae J233(T) with a 16S rRNA gene sequence similarity of 90.5%. Based on the results of polyphasic analysis, the name Mariniplasma anaerobium gen. nov., sp. nov. is proposed to accommodate strain Mahy22(T), along with reclassification of some Acholeplasma species into Alteracholeplasma gen. nov., Haploplasma gen. nov. and Paracholeplasma gen. nov.

Automated summary

A novel strictly anaerobic chemoorganotrophic bacterium, Mahy22(T), isolated from a shallow brackish meromictic lake in Japan, showed unique morphology and growth conditions. Phylogenetic analysis based on the 16S rRNA gene placed the strain in a new genus, Mariniplasma anaerobium gen. nov., distinct from other Acholeplasma species.