Sphingosinicella microcystinivorans gen. nov., sp nov., a microcystin-degrading bacterium

Three strains of bacteria that degrade the cyanobacterial hepatotoxin microcystin, Y2(T), MDB2 and MDB3, were isolated from a eutrophic lake, Lake Suwa, and the Tenryu River, Japan, and characterized. These strains were aerobic and chemo-organotrophic and their cells were Gram-negative, non-spore-forming rods, motile by means of single polar flagella. Yellow-pigmented colonies were formed on nutrient agar media. The strains assimilated only citrate among the organic compounds tested as carbon sources. The G + C content of genomic DNA ranged from 63.6 to 63.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the new isolates formed a tight cluster within the family Sphingomonadaceae but were clearly separate from established genera of this family, e.g. Sphingomonas, Sphingobium, Novosphingobium, and Sphingopyxis; sequence similarities between the new isolates and type strains from established genera ranged from 90.9 to 94.9%. Chemotaxonomic and phenotypic data supported the conclusion that these strains were members of the family Sphingomonadaceae. The major components of the cellular fatty acids were 18:1 omega 7c (36-41%) and 16:1 omega 7c (33-36%). Hydroxy fatty acids were mainly 2-OH 14: 0 (11-13%), and 3-OH fatty acids were absent. Glycosphingolipids were detected. Ubiquinone-10 and homospermidine were present as the major quinine and polyamine, respectively. Thus, it is proposed that the three strains represent a new genus and species of the family Sphingomonadaceae with the name Sphingosinicella microcystinivorans gen. nov., sp. nov. The type strain is Y2(T) (= KCTC; 12019(T)=JCM 13185(T)).