Modulation of Type III Secretion System in Pseudomonas aeruginosa: Involvement of the PA4857 Gene Product

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen that causes serious acute or chronic infections in humans. Acute infections typically involve the type III secretion systems (T3SSs) and bacterial motility, whereas chronic infections are often associated with biofilm formation and the type VI secretion system. To identify new genes required for pathogenesis, a transposon mutagenesis library was constructed and the gene PA4857, named tspR, was found to modulate T3SS gene expression. Deletion of P. aeruginosa tspR reduced the virulence in a mouse acute lung infection model and diminished cytotoxicity. Suppression of T3SS gene expression in the tspR mutant resulted from compromised translation of the T3SS master regulator ExsA. TspR negatively regulated two small RNAs, RsmY and RsmZ, which control RsmA. Our data demonstrated that defects in T3SS expression and biofilm formation in retS mutant could be partially restored by overexpression of tspR. Taken together, our results demonstrated that the newly identified retS-tspR pathway is coordinated with the retS-gacS system, which regulates the genes associated with acute and chronic infections and controls the lifestyle choice of P. aeruginosa.

Characterizing and contrasting the microbial ecology of laboratory and full-scale EBPR systems cultured on synthetic and real wastewaters

“…While most other data sets did not exhibit the coverage to justify significant conclusions, Propionivibrio nonetheless was commonly observed (in many instances dominating; Tables S92). Functionally, Propionivibrio is a fermentative bacterium with the capability to produce short-chain VFAs (i.e., the optimal EBPR substrate) from polysaccharides (Zhou et al 2015); given these metabolic capabilities, certain species of Propionivibrio could be PAOs, although recent research has identified one potential species ( Candidatus Propionivibrio aalborgensis) as a putative GAO (Albertsen et al 2016). Other genera including Azonexus and Dechloromonas (within the Rhodocyclaceae family of the Betaproteobacteria class) were observed, as was Bdellovibrio (which is within the Bdellovibrionaceae family of the Deltaproteobacteria class).…”

PCB dechlorination hotspots and reductive dehalogenase genes in sediments from a contaminated wastewater lagoon

“…A recent report implicated Geobacteraceae in PCB dechlorination processes in sediment-free microcosms in part because of a negative correlation between this group and the abundance of penta-chlorinated PCBs (penta-CBs) (Praveckova et al 2016). It is currently unclear whether Geobacteraceae directly participate in PCB dechlorination processes or enhance dechlorination in some way such as contributing essential cobalamin cofactors to relevant Dehalococcoides sp.…”

“…(Firmicutes) in Aroclor 1242 dechlorination (Hou and Dutta 2000). Recent evidence indicates Geobacteraceae (δ-Proteobacteria) may play a role in PCB dechlorination (Praveckova et al 2016). …”

The Central Nervous System and the Gut Microbiome

“…The maternal microbiome is distinct and dynamically changing during pregnancy compared to other periods in female life (DiGiulio et al, 2015; Koren et al, 2012; MacIntyre et al, 2015; Nuriel-Ohayon et al, 2016; Romero et al, 2014a). With the progression of pregnancy, various taxa change in abundance with some becoming more dominant over others.…”

“…E-embryonic age, P-postnatal age, GSW-gestational week. Bacterial taxa on the right panel are the dominant ones at each life stage (Bäckhed et al, 2015; Lloyd-Price et al, 2016b; Nuriel-Ohayon et al, 2016). …”