[Variable fragment of 23S rDNA for classification and identification of Xenorhabdus].
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.


CONCLUSIONS
The 23S rDNA fragment can be used to identify Xenorhabdus, especially for a large number of Xenorhabdus strains obtained from field survey.
State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China. jingxiu_zhao@yahoo.cn
Jingxiu
J
Zhao
Chunlin
C
Liu
Lihong
L
Qiu
Yi
Y
Pang
D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics*; D017422:Sequence Analysis, DNA; D020593:Xenorhabdus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification
D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S