Paucibacter toxinivorans gen. nov., sp. nov., a bacterium that degrades cyclic cyanobacterial hepatotoxins microcystins and nodularin

Thirteen bacterial isolates from lake sediment, capable of degrading cyanobacterial hepatotoxins microcystins and nodularin, were characterized by phenotypic, genetic and genomic approaches. Cells of these isolates were Gram-negative, motile by means of a single polar flagellum, oxidase-positive, weakly catalase-positive and rod-shaped. According to phenotypic characteristics (carbon utilization, fatty acid and enzyme activity profiles), the G+C content of the genomic DNA (66.1-68.0 mol%) and 16S rRNA gene sequence analysis (98.9-100% similarity) the strains formed a single microdiverse genospecies that was most closely related to Roseateles depolymerans (95.7-96.3% 16S rRNA gene sequence similarity). The isolates assimilated only a few carbon sources. Of the 96 carbon sources tested, Tween 40 was the only one used by all strains. The strains were able to mineralize phosphorus from organic compounds, and they had strong leucine arylamidase and chymotrypsin activities. The cellular fatty acids identified from all strains were C(16:0) (9.8-19%) and C(17:1)omega7c (<1-5.8%). The other predominant fatty acids comprised three groups: summed feature 3 (<1-2.2%), which included C(14:0) 3-OH and C(16:1) iso I, summed feature 4 (54-62%), which included C(16:1)omega7c and C(15:0) iso OH, and summed feature 7 (8.5-28%), which included omega7c, omega9c and omega12t forms of C(18:1). A more detailed analysis of two strains indicated that C(16:1)omega7c was the main fatty acid. The phylogenetic and phenotypic features separating our strains from recognized bacteria support the creation of a novel genus and species, for which the name Paucibacter toxinivorans gen. nov., sp. nov. is proposed. The type strain is 2C20(T) (=DSM 16998(T)=HAMBI 2767(T)=VYH 193597(T)).