Our identification of mutants in pbgPE, galE and galU clearly implicates LPS as an important player in the colonization of the IJ by Photorhabdus. In this study we also identified mutations in genes that were not directly associated with LPS metabolism; asmA, hdfR and proQ. The asmA gene was originally identified in E. coli as a site for suppressor mutations of an assembly defective porin, OmpF315 [23]. Although the role of AsmA is still not clear it is likley that this

protein is involved in organising the outer membrane. In the first instance a mutation in asmA has been shown to result in reduced levels of LPS in the outer membrane Pifithrin-�� price of E. coli [12]. In addition a recent study reported that a mutation in asmA in Salmonella enterica serovar Typhimurium resulted in a remodelling Selleck TSA HDAC of the outer membrane that resulted in an increase in the transcription of marAB, encoding a multi-drug efflux pump [24]. The authors further report that the S. enterica

asmA mutant was attenuated in virulence when administered orally to mice and showed a reduced ability to invade epithelial cells thus linking asmA with infection [24]. The hdfR gene was originally annotated as 2 overlapping genes, yifA and pssR, on the E. coli genome but recent analysis confirmed the presence of a sequencing error that resulted in a frameshift and the subsequent mis-annotation [14, 25]. The hdfR gene is predicted to encode a LysR-type regulator that represses the expression of flhDC, and therefore motility, in E. coli [14]. In Proteus mirabilis 2 independent mutations in hdfR were identified in a STM experiment as being important for urinary tract colonization in mice [26]. Motility has been shown to play an important role in P. mirabilis virulence however a role for hdfR in regulating motility http://www.selleck.co.jp/products/Rapamycin.html in Proteus has not been determined [27]. Interestingly we have shown that the hdfR mutant does not appear

to affect swimming motility in P. luminescens (data not shown). Finally we identified a mutation in the proQ gene. This gene is predicted to encode a protein that, in E. coli, is involved in the post-translational activation of ProP, an osmoprotectant/proton symporter that is capable of transporting both proline and glycine betaine in response to increases in osmotic pressure [15, 16]. However the genome of P. luminescens is not predicted to encode a ProP homologue suggesting an alternative role for ProQ in Photorhabdus. Interestingly the proQ mutant was the most affected in attachment to an abiotic surface suggesting alterations in the cell surface of the mutant (see Figure 3). However the proQ mutant was not sensitive to CAMPs suggesting that the LPS was not affected (see Figure 5). It is also noteworthy that, unlike the other mutants identified in this study, there is the possibility that the mutation in proQ has a polar affect on the downstream gene, prc (see Figure 2). The proQ and prc genes are separated by 20 bp on both the E.