A numerical taxonomic study of the genus Xenorhabdus (Enterobacteriaceae) and proposed elevation of the subspecies of X. nematophilus to species.

Data from a study of both phases of 21 strains of Xenorhabdus examined for 240 characters were subjected to numerical analysis. Only 60 characters were used for the analyses, since 169 characters were common to all isolates, and the acidification data essentially duplicated the assimilation tests. The data were arranged in seven ways to determine the significance of characters affected by phase change and of weak responses. Most of the analyses involved calculation of similarities by the Jaccard coefficient and clustering by single linkage, complete linkage and centroid sorting algorithms. The resultant dendrograms emphasized the importance of recognizing phase-related characteristics in examining the taxonomy of Xenorhabdus. They also demonstrated a close correspondence between the taxonomic groupings of Xenorhabdus and those of their nematode associates. It is proposed that the subspecies of X. nematophilus be elevated to species, X. nematophilus, X. bovienii, X. poinarii and X. beddingii.