CHEMOTAXONOMIC STUDY OF XENORHABDUS SPECIES - CELLULAR FATTY-ACIDS, UBIQUINONE AND DNA-DNA HYBRIDIZATION

Four strains of Xenorhabdus nematophilus, one strain each of "Xenorhabdus poinarii" and "Xenorhabdus bovienii" were isolated from the nematode Steinernema spp., and identified. The chemotaxonomic characteristics were studied in these six isolates and in three authentic strains containing Xenorhabdus luminescens. In X. nematophilus, "X. poinarii" and "X. bovienii," the major cellular fatty acids were C16:0, C16:1, C18:1, and C17-cy acids. In X. luminescens, they were C16:0, C(i-15), C18:1, and C16:1 acids. The respiratory quinone system was ubiquinone-8 in all strains. The guanine plus cytosine contents of the DNA of the strains used were 43.3 to 45.2 mol%. The DNA homology values were higher than 76% among five strains of X. nematophilus, including the type strain, and a strain of "X. poinarii." For these strains, "X. bovienii" showed homology values less than 46%. The values of X. nematophilus, "X. poinarii" and "X. bovienii" to X. luminescens were about 15%. The DNA homology value between X. luminescens ATCC 29999T (type strain) and X. luminescens ATCC 29304 was 51%, suggesting the heterogeneity of the species. These results indicate the synonymy of X. nematophilus and "X. poinarii," and verify "X. bovienii" and X. luminescens as distinct species.