رویکردی جامع در شناسایی نماتود بیمارگر حشرات Steinernema siamkayai و باکتری همزیستش، Xnoehabdus stockiae با استناد به داده های مولکولی و فنوتیپی

We present the characterization of the entomopathogenic nematode isolate LD_CU, and its associated symbiotic entomopathogenic bacteria. Morphological data of the present strain showed similitude with type population of Steinernema siamkayai, with small morphometric variations. BLASTn analysis of the ITS rRNA sequence of the nematode revealed ۱۰۰% similarity with S. siamkayai, confirming conspecificity. The pairwise alignment showed no nucleotide differences with the type population of S. siamkayai. Phylogenetic analysis based on ITS rRNA gene sequences supported these findings, placing isolate LD_CU in a monophyletic clade with S. siamkayai, which forms a sister clade with S. huense, S. cumgarense, S. tami, and S. minutum. Biochemical tests identified the associated bacterial symbiont as Xenorhabdus stockiae. The isolate tested negative for oxidase, catalase, nitrate reductase, O-Nitrophenyl-β-D galactopyranoside (ONPG), methyl red, tryptophan deaminase, indole production, ornithine, lysine, citrate, malonate, hydrogen sulfide, acetoin, and phenylalanine deaminase, but positive for urea and esculin hydrolysis, motility, and acid production from glucose fermentation. The bacteria exhibited neutral red adsorption on MacConkey agar and formed brownish pigmented colonies on nutrient agar. Molecular characterization using ۱۶S rRNA gene sequences revealed ۱۰۰% similarity with X. stockiae and ۹۰% similarity with X. innexi, indicating significant divergence from other Xenorhabdus species. Phylogenetic analysis showed a close relation to X. stockiae VP-۲۰۱۶b and distinct differences from X. innexi DSM ۱۶۳۳۶T. Pairwise alignment confirmed no nucleotide differences between the present bacterial strain and X. stockiae. This detailed and comprehensive profiling supports the accurate identification of Steinernema siamkayai and its bacterial symbiont, Xenorhabdus stockiae, and contributes valuable information to the taxonomy and phylogeny of these organisms.

Keywords:

BLAST , ITS rRNA , Steinernema siamkayai , Xenorhabdus stockiae , ۱۶S rRNA