Description of Immundisolibacter cernigliae gen. nov., sp. nov., a high-molecular-weight polycyclic aromatic hydrocarbon-degrading bacterium within the class Gammaproteobacteria, and proposal of Immundisolibacterales ord. nov. and Immundisolibacteraceae fam. nov.

The bacterial strain TR3.2T was isolated from aerobic bioreactor-treated soil from a polycyclic aromatic hydrocarbon (PAH)-contaminated site in Salisbury, NC, USA. Strain TR3.2T was identified as a member of 'Pyrene Group 2' or 'PG2', a previously uncultivated cluster of organisms associated with the degradation of high-molecular-weight PAHs by stable-isotope probing. Based on its 16S rRNA gene sequence, the strain was classified as a member of the class Gammaproteobacteria but possessed only 90.5 % gene identity to its closest described relative, Methylococcus capsulatus strain Bath. Strain TR3.2T grew on the PAHs pyrene, phenanthrene, anthracene, benz[a]anthracene and fluorene, as well as the azaarene carbazole, and could additionally metabolize a limited number of organic acids. Optimal growth occurred aerobically under mesophilic temperature, neutral pH and low salinity conditions. Strain TR3.2T was catalase and oxidase positive. Predominant fatty acids were C17 : 0 cyclo and C16 : 0. Genomic G+C content of the single chromosome was 67.79 mol% as determined by complete genome sequencing. Due to the high sequence divergence from any cultivated species and its unique physiological properties compared to its closest relatives, strain TR3.2T is proposed as a representative of a novel order, family, genus and species within the class Gammaproteobacteria, for which the name Immundisolibacter cernigliae gen. nov., sp. nov. is proposed. The associated order and family are therefore proposed as Immundisolibacteralesord. nov. and Immundisolibacteraceaefam. nov. The type strain of the species is TR3.2T (=ATCC TSD-58T=DSM 103040T).