Regulation of two genes, MigA and wapR, involved in core LPS biosynthesis in Pseudomonas aeruginosa
Two putative glycosyltransferases, encoded by 'migA' and ' wapR', are involved in the biosynthesis of the LPS core oligosaccharide of 'Pseudomonas aeruginosa'. The focus of this thesis is to examine the expression and regulation of 'migA' and ' wapR'. The first goal was to determine if differential expression of 'migA' and 'wapR' affected lipopolysaccharide (LPS) production. A gene-dosage effect was observed when 'migA' or 'wapR' mutants were complemented with homologous genes using a pUCP26 construct that gave high-copy gene expression. Modification of the proportion of LPS molecules was observed. In contrast, this effect was not observed when complementation was achieved using a minictx2 vector that gave native single copy expression. The second goal was to determine if ' migA' and 'wapR' are differentially expressed, and by what mechanism. Putative quorum sensing (QS) transcription factor binding motifs were identified upstream of 'wapR' by 'in-silico ' analysis, which suggested that 'wapR' was regulated by one of the QS systems. QS regulates the expression of many genes based on cell-density. Real-time quantitative PCR analysis of 'migA' and 'wapR' expression in wild-type and QS mutants was performed and the data suggested that the RhlRI QS system differentially regulates ' migA' and 'wapR' expression in 'P. aeruginosa ' PAO1.