TAXONOMIC STUDY OF POLYETHYLENE GLYCOL-UTILIZING BACTERIA - EMENDED DESCRIPTION OF THE GENUS SPHINGOMONAS AND NEW DESCRIPTIONS OF SPHINGOMONAS-MACROGOLTABIDUS SP-NOV, SPHINGOMONAS-SANGUIS SP-NOV AND SPHINGOMONAS-TERRAE SP-NOV

The taxonomic position of polyethylene glycol (PEG)-utilizing bacteria was examined. PEG 4,000 was utilized by a single pure culture, but PE G 6,000 was utilized by mixed cultures of two strains. PEG 4,000-utili zing bacteria and the dominant bacteria in the PEG 6,000-utilizing mix ed cultures which are responsible for the degradation of PEG were iden tified as new species of the genus Sphingomonas, based on chemotaxonom ic and physiological characteristics together with DNA/DNA hybridizati on studies and 16S rRNA sequence comparison, and we propose two new sp ecies, Sphingomonas macrogoltabidus (type strain: 203, IFO 15033) for the PEG 4,000-utilizing bacteria and Sphingomonas terrae (type strain: E-1-A, IFO 15098) for the PEG 6,000-utilizing bacteria. And we also p ropose Sphingomonas sanguis for the remaining one strain, Sphingomonas genospecies 1 (type strain: IFO 13937). Emended description of the ge nus Sphingomonas is presented. The other bacteria in the 6,000-utilizi ng mixed cultures, which support the growth of the dominant bacteria b y degrading an inhibitory substance, glyoxylate, were tentatively iden tified as Rhizobium sp., Agrobacterium sp. and Methylobacterium sp. Fo ur isolates which utilize PEGs having molecular weights lower than 4,0 00 were identified as Pseudomonas solanacearum, Alcaligenes xylosoxida ns subsp. denitrificans, Enterobacter diversus and Pseudomonas vesicul aris.