TAXONOMIC STUDY OF AROMATIC-DEGRADING BACTERIA FROM DEEP-TERRESTRIAL-SUBSURFACE SEDIMENTS AND DESCRIPTION OF SPHINGOMONAS-AROMATICIVORANS SP-NOV, SPHINGOMONAS-SUBTERRANEA SP-NOV, AND SPHINGOMONAS-STYGIA SP-NOV

Phylogenetic analyses of 16S rRNA gene sequences by distance matrix an d parsimony methods indicated that six strains of bacteria isolated fr om deep saturated Atlantic coastal plain sediments were closely relate d to the genus Spltingomonas. Five of the strains clustered with, but were distinct from, Sphingomonas capsulata, whereas the sixth strain w as most closely related to Blastobacter natatorius. The five strains t hat clustered with S. capsulata, all of which could degrade aromatic c ompounds, were gram-negative, non-spore-forming, nonmotile, rod shaped organisms that produced small, yellow colonies on complex media. Thei r G + C contents ranged from 60.0 to 65.4 mol%, and the predominant is oprenoid quinone was ubiquinone Q-10. All of the strains were aerobic and catalase positive. Indole, urease, and arginine dihydrolase were n ot produced. Gelatin was not liquified, and glucose was not fermented. Sphingolipids were present in all strains; 2OH14:0 was the major hydr oxy fatty acid, and 18:1 was a major constituent of cellular lipids. A cid was produced oxidatively from pentoses, hexoses, and disaccharides , but not from polyalcohols and indole. All of these characteristics i ndicate that the five aromatic-degrading strains should be placed in t he genus Sphingomonas as currently defined. Phylogenetic analysis of 1 6S rRNA gene sequences, DNA-DNA reassociation values, BOX-PCR genomic fingerprinting, differences in cellular lipid composition, and differe nces in physiological traits all indicated that the five strains repre sent three previously undescribed Sphingomonas species. Therefore, we propose the following new species: Sphingomonas ar aromaticivorans (ty pe strain, SMCC P199), Sphingomonas subterranea (type strain, SMCC B04 78), and Sphingomonas stygia (type strain, SMCC B0712).