luminescens genomes and proQ and prc are predicted to be on the same transcription unit in E. coli http://ecocyc.org. The prc gene encodes a periplamsic protease
called Prc or Tsp (tail-specific protease) that processes the C-terminus of FtsI (PBP3) and is selleck products required for protection from combined osmotic and thermal stress [28, 29]. Moreover Prc has been shown to interact with NlpI, a lipoprotein that has recently been shown to be involved in the attachment of adherent-invasive E. coli (bacteria associated with Crohns disease) to epithelial cells [30, 31]. In addition, in Pseudomonas aeruginosa, Prc has been Selleckchem Combretastatin A4 implicated in the regulation of alginate production by degrading mutant forms of MucA, the anti-sigma factor that interacts with the alternative sigma factor AlgU . Therefore a decrease in the level of prc transcription may affect the surface of Photorhabdus in a way that prevents colonization of the IJ. However further experimentation is required to determine whether the proQ or prc gene (or both) are responsible for the reported phenotype. Conclusion We have identified 5 genetic loci in P. luminescens TT01 that are affected find more in their ability to colonize IJs of the nematode H. bacteriophora. In order to have a reduced transmission frequency it
would be expected that the mutants would be affected in either their ability to infect and replicate within the adult hermpahrodite or in their ability to colonize the IJ. Preliminarly studies, Alanine-glyoxylate transaminase using confocal laser scanning microscopy (CLSM), suggest that all of the mutants are able to infect the adult hermaphrodite (our unpublished data). Therefore the defect in colonization appears to occur at some point later during the transmission process. It has been shown that colonization of the IJ requires binding to the pre-intestinal valve cell in the immature IJ followed by growth and replication of the bacteria in the gut lumen . All of the mutants identified in this study can be implicated in the maintenance of the structure and/or remodelling the bacterial cell surface and it is, therefore, easy to envisage how mutations affecting the cell surface of P. luminescens could affect
how the bacteria interact with the IJ. The exact stage and nature of the colonization defect of each mutant is currently under examination. Methods Bacterial strains and culture conditions All P. luminescens strains were cultured in LB broth or on LB agar (LB broth plus 1.5% (w/v) agar) at 30°C. Unless otherwise stated all LB agar plates were supplemented with 0.1% (w/v) pyruvate. When required antibiotics were added at the following concentrations: ampicillin (Ap), 100 μg ml-1; chloramphenicol (Cm), 20 μg ml-1; gentamycin (Gm), 20 μg ml-1; kanamycin (Km), 25 μg ml-1and rifampicin (Rif), 50 μg ml-1. Construction of gfp-tagged P. luminescens TT01 A gfp-tagged strain of P. luminescens TT01 was constructed using the Tn7-based vector, pBKminiTn7-gfp2 . Overnight cultures of P. luminescens TT01 (the recipient), E.