Increased expression of genes encoding products for synthesis of LPS, peptidoglycan and capsular polysaccharide may be linked to extracytoplasmic stress response activation to neutralize the compromised #FK228 price randurls[1|1|,|CHEM1|]# cell envelope. We had previously shown that the tolC mutant strain is unable to produce succinoglycan in GMS medium [15]. Whether that was related to differences

at transcriptional level or to post-transcriptional regulation was unknown. exo gene expression is positively regulated by the regulator MucR [44] and negatively by ExoR [45]. Here mucR gene expression was significantly increased whilst exoR was decreased when Selleckchem Thiazovivin the transcription profile of the tolC mutant was compared to that of the wild-type strain. This could suggest increased expression of the exo genes directing succinoglycan biosynthesis in the tolC mutant. However, none of the exo genes had significant changes at the level of expression, with the exception of exoN encoding UDP-glucose pyrophosphorylase, which showed decreased expression, and the gene exoU encoding a glycosyltransferase the expression of which was increased. Apparently the absence of succinoglycan from the tolC mutant is not caused by differences at the transcription level. It appears more probable that, due to

cell envelope perturbations, the exopolysaccharide polymerization and secretion multienzyme else complex does not assemble properly or is inactive and therefore no exopolysaccharide is secreted. Also no difference was observed in the expression of genes involved in galactoglucan biosynthesis, with the exception of the transcriptional activator encoding gene wggR [46] that showed a decreased expression. Our

results contrast with those obtained for S. meliloti cells stressed with salt or acid pH, where genes encoding proteins for exopolysaccharide biosynthesis showed increased expression [30, 33]. Genes involved in motility and chemotaxis Analysis of gene expression levels in the flagellar regulon indicated an approximately 2-fold increased expression in the tolC mutant of cheABDRW1W2XY1Y2 and mcpU genes, whose products are involved in chemotaxis. Most of the fli, flh, mot, flg and fla genes encoding proteins for the basal body, L and P rings, hook filament, motor switch and flagellum also displayed increased expression in the tolC mutant (Table 1). To test whether differences in the expression of motility genes leads to a phenotype in GMS semi-solid media, swimming and swarming tests were performed using the two strains. Two further strains used in this test were an S.