Recent studies in our lab have shown that PA3133 (sawR), a probable transcription factor of P. aeruginosa, is over-expressed in response to Surface Acoustic Waves (SAW). SAW is known to affect P. aeruginosa biofilm formation and antibiotic resistance. In this study we attempt to uncover the role of sawR in regulating these phenotypes.
We utilized a laboratory flow cell system and were able to demonstrate that the biofilm of sawR over-expressing strain is highly sensitive to antibiotic treatment and forms less biomass than the wild type (WT) strain, as observed when the WT strain was exposed to SAW.
In order to examine the genetic effects of an over-expressing sawR strain, we performed a microarray experiment in which we compared gene expression levels of a sawR over-expressing strain to the WT strian. We observed high expression levels of a regulon composed off 11 genes responsible for choline/glycine-betaine catabolism. This regulon is regulated by gbdR, which was also significantly increased in the sawR over-expressing strain. Another phenotype of the sawR over expressing strain is the accumulation of pyomelanin, a brown pigment that is known to reduce oxidative stress. This phenotype was corroborated by our microarray results, as hmgA, a gene in the phenylalanine/tyrosine metabolic pathway, was down-regulated in the sawR over-expressing strain. It is known that in the absence of hmgA, strains hyper-produce pyomelanin. Taken together our data suggest that sawR has a central role in mediating the response to SAW and key phenotypes such biofilm formation, antibiotic resistance and pigment production.
