Document Type : Paper, English
Authors
1
Department of Biosciences, Chandigarh University, Mohali 140413, Punjab, India
2
Department of Biosciences, Chandigarh University, Mohali, Punjab, 140413, India
10.61186/jesi.44.4.12
Abstract
We present the characterization of the entomopathogenic nematode isolate LD_CU, and its associated symbiotic entomopathogenic bacterium. BLASTn analysis of the ITS rRNA sequence of the nematode revealed 100% similarity with Steinernema 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 16S rRNA gene sequences revealed 100% similarity with X. stockiae and 90% similarity with X. innexi, indicating significant divergence from other Xenorhabdus species. Phylogenetic analysis showed a close relation to X. stockiae VP-2016b and distinct differences from X. innexi DSM 16336T. 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.
Graphical Abstract
Keywords
Main Subjects
)
)