The GacS/GacA signal transduction system of Pseudomonas aeruginosa acts exclusively through its control over the transcription of the RsmY and RsmZ regulatory small RNAs

Abstract

SummaryWe report here the results of an analysis of the regulatory range of the GacS/GacA two-component system in Pseudomonas aeruginosa. Using microarrays, we identified a large number of genes that are regulated by the system, and detected a near complete overlap of these genes with those regulated by two small RNAs (sRNAs), RsmY and RsmZ, suggesting that the expression of all GacA-regulated genes is RsmY/Z-dependent. Using genome-wide DNA-protein interaction analyses, we identified only two genomic regions that associated specifically with GacA, located upstream of the rsmY and rsmZ genes. These results demonstrate that in P. aeruginosa, the GacS/ GacA system transduces the regulatory signals to downstream genes exclusively by directly controlling the expression of only two genes rsmY and rsmZ. These two sRNAs serve as intermediates between the input signals and the output at the level of mRNA stability, although additional regulatory inputs can influence the levels of these two riboregulators. We show that the A+T-rich DNA segment upstream of rsmZ is bound and silenced by MvaT and MvaU, the global gene regulators of the H-NS family. This work highlights the importance of post-transcriptional mechanisms involving sRNAs in controlling gene expression during bacterial adaptation to different environments.

Genetic and phenotypic analysis of the GacS/GacA system in the moderate halophile Halomonas anticariensis

“…In the case of P. aeruginosa PAO1, however, it has been suggested that the GacS/GacA TCS regulates the production of AHLs, which have a positive effect upon the induction of rpoS expression, which in turn activates genes expressed mainly during the stationary phase, such as those encoding the production of several virulence factors, including pyocyanine, exotoxin A, elastase and lipase enzymes and type III secretion system among others (Hogardt et al, 2004;Latifi et al, 1995;Reimmann et al, 1997;Winson et al, 1995;Winzer et al, 2000). Furthermore, it has been reported that this signal transduction system in this bacterium acts exclusively by controlling the transcription of the RsmY and RsmZ regulatory small RNAs (Brencic et al, 2009). This second regulatory pathway may not be viable in H. anticariensis FP35 T , however, since we have found that its EPS production is not controlled by AHLs (data not shown).…”

An unusual CsrA family member operates in series with RsmA to amplify posttranscriptional responses inPseudomonas aeruginosa

“…Because RsmA is required for maximal T3SS gene expression (7,9,22), we hypothesized that RsmF may play a similar role in controlling T3SS gene expression. To test this hypothesis, we introduced a T3SS-dependent reporter gene (P exsD-lacZ ) (23) into the ectopic ΦCTX attachment site on the chromosome of wild-type strain PA103 and the rsmA, rsmF, and rsmAF mutants.…”

Dispersed cells represent a distinct stage in the transition from bacterial biofilm to planktonic lifestyles

“…RsmY and RsmZ are known to negatively regulate type III secretion in P. aeruginosa by antagonizing RsmA, a posttranscriptional regulator 29,30 . A DrsmYDrsmZ double mutant has a higher level of type III secretion and is more virulent than single DrsmY or DrsmZ mutants 31 . Because the expressions of both rsmY and rsmZ were lower in dispersed cells than they were in planktonic cells, we hypothesized that dispersed cells could activate their type III secretion and thus be more virulent to macrophages than planktonic cells.…”