Description of chlorophenol-degrading Pseudomonas sp. strains KF1T, KF3, and NKF1 as a new species of the genus Sphingomonas, Sphingomonas subarctica sp. nov.

Gram-negative polychlorophenol-degrading bacterial strains KF1T (T = type strain), KF3, and NKF1, which were described previously as Pseudomonas saccharophila strains, were studied by chemotaxonomic, genetic, and physiological methods and by electron microscopy and compared with selected xenobiotic compound-degrading bacteria. These strains contained sphingolipids with d-18:0, d-20:1, and d-21:1 as the main dihydrosphingosines, ubiquinone 10 as the main respiratory quinone, and spermidine as the major polyamine, and the DNA G + C content was 66 mol%. The cellular fatty acids included about 60% octadecenoic acid, 9% 2-hydroxymyristic acid, 14% cis-9-hexadecenoic acid, and 10% hexadecanoic acid. These strains exhibited less than 97% 16S ribosomal DNA sequence similarity to all of the other taxa studied. In the DNA-DNA reassociation studies the highest levels of reassociation between these strains and previously described species were less than 40%. Thin sections of cells of strains KF1T, KF3, and NKF1 were examined by electron microscopy, and the results showed that the cells had peculiar concentrically arranged layered membranous blebs that extruded from the outer membrane, especially at the cell division points. On the basis of the results of this study, polychlorophenol-degrading strains KF1T, KF3, and NKF1 are considered members of a new species of the genus Sphingomonas, Sphingomonas subarctica. The polycyclic aromatic hydrocarbon-degrading organism Sphingomonas paucimobilis EPA 505 was closely related to Sphingomonas chlorophenolica as determined by chemotaxonomic, phylogenetic, and physiological criteria. The xenobiotic compound degraders Alcaligenes sp. strain A175 and Pseudomonas sp. strain BN6 were identified as members of species of the genus Sphingomonas.