Gene expression in Moraxella osloensis, Photorhabdus temperata and Xenorhabdus koppenhoeferi during host infection

Bacterium Moraxella osloensis is associated with slug-parasitic nematode Phasmarhabditis hermaphrodita, and bacteria from genus Photorhabdus and Xenorhabdus are with entomopathogenic nematode Heterorhabditis and Steinernema , respectively.;We first determined gene expression of M. osloensis in the mollusk host Deroceras reticulatum by selective capture of transcribed sequences (SCOTS) technique. Two genes, ubiquinone synthetase (ubiS) and acyl-coA synthetase (acs) were up-regulated in both D. reticulatum and stationary phase in vitro cultures. Eleven genes were exclusively expressed in D. reticulatum and were thus infection specific. Mutational analysis on genes of protein-disulfide isomerase (dsbC) and ubiS confirmed that UbiS is important to M. osloensis growth and DsbC serves as a virulence factor.;Bacteria Photorhabdus temperata and Xenorhabdus koppenhoeferi, the symbionts of nematodes Heterorhabditis bacteriophora and Steinernema scarabaei, respectively, were virulent to three white grub species Popillia japonica, Rhizotrogus majalis, and Cyclocephala borealis. The median lethal dose at 48h post injection and median lethal time at injection dose of 20 cells per grub showed that P. temperata was more virulent than X. koppenhoferi to C. borealis. However, although P. temperata grew faster than X. koppenhoeferi both in vitro and in vivo, there were no differences in virulence of two bacteria against R. majalis and P. japonica. Using SCOTS technique, 30 genes by P. temperata and 25 by X. koppenhoeferi were identified to be differentially expressed during infection to R. majalis. Most genes were unique to either P. temperata or X. koppenhoeferi, e.g. ttsL encoding a type III secretion system was only identified from P. temperata , and lpsE corresponding to lipopolysaccharide synthesis was unique to X. koppenhoeferi. Five nexus genes directly connecting to several other genes were identified as attractive candidates for future studies using the metabolic computational pathway analysis. Compared to the gene expression of M. osloensis, several common genes were found to be up-regulated during infection in all three bacteria, including dsb gene family and genes encoding outer membrane proteins, fatty acid synthesis proteins, and ubiquinone synthesis proteins.