Variable fragment of 23S rDNA for classification and identification of Xenorhabdus
以23S rDNA一个多变区作为分子标记对致病杆菌属细菌进行分类鉴定

Objective]Members of Xenorhabdus are symbiotic bacteria of entomopathogenic nematodes Steinernema,and can be applied as biopesticides against insects.Therefore,a rapid and accurate method for classification and identification of Xenorhabdus is essential.Methods] An 845bp-fragment of 23S rDNA sequence of 26 strains of Xenorhabdus representing 20 described species was PCR amplified and sequenced.A phylogenetic tree of Xenorhabdus based on the sequences obtained was constructed and compared to that based on nearly complete 16S rDNA sequences for suitability as molecular maker for classification and identification of Xenorhabdus.Results] The 23S rDNA fragment contained more variable and parsimony-informative sites proportionally,and with greater pairwise distances among sequences compared to those of 16S rDNA.Conclusion] The 23S rDNA fragment can be used to identify Xenorhabdus,especially for a large number of Xenorhabdus strains obtained from field survey.