ClpP deletion causes attenuation of Salmonella Typhimurium virulence through mis-regulation of RpoS and indirect control of CsrA and the SPI genes

TY - JOUR

T1 - ClpP deletion causes attenuation of Salmonella Typhimurium virulence through mis-regulation of RpoS and indirect control of CsrA and the SPI genes

AU - Knudsen, Gitte Maegaard

AU - Olsen, John Elmerdahl

AU - Aabo, Søren

AU - Barrow, Paul

AU - Rychlik, Ivan

AU - Thomsen, Line E

PY - 2013/7

Y1 - 2013/7

N2 - Salmonella enterica serovar Typhimurium requires the type III secretion system encoded by Salmonella pathogenicity island 1 (SPI1) and controlled by the master regulator, HilA, to penetrate the intestinal epithelium. Numerous regulators affect virulence through influence on this system, including the proteolytic component ClpP, the stationary phase regulator RpoS and the carbon-storage regulator CsrA. However, the mechanism behind the ClpP regulation is not fully understood. To elucidate this we examined differentially expressed genes in a DclpP mutant compared with WT using global transcriptomic analysis. SPI1 and SPI4 virulence genes were significantly downregulated in the ΔclpP mutant, whereas several RpoS-dependent genes and the fliC gene encoding flagellin were upregulated. While the DclpP mutant was attenuated in cell invasion, this attenuation was not present in a ΔclpP/rpoS:: amp double mutant, suggesting the repression of invasion was directed through RpoS. The expression of the csrA virulence regulator was increased in the ΔclpP mutant and decreased in the rpoS:: amp and ΔclpP/rpoS:: amp mutants, indicating that ClpP affects the csrA expression level as well. Thus, this study suggests that ClpP affects SPI1 expression and thereby virulence indirectly through its regulation of both RpoS and CsrA.

AB - Salmonella enterica serovar Typhimurium requires the type III secretion system encoded by Salmonella pathogenicity island 1 (SPI1) and controlled by the master regulator, HilA, to penetrate the intestinal epithelium. Numerous regulators affect virulence through influence on this system, including the proteolytic component ClpP, the stationary phase regulator RpoS and the carbon-storage regulator CsrA. However, the mechanism behind the ClpP regulation is not fully understood. To elucidate this we examined differentially expressed genes in a DclpP mutant compared with WT using global transcriptomic analysis. SPI1 and SPI4 virulence genes were significantly downregulated in the ΔclpP mutant, whereas several RpoS-dependent genes and the fliC gene encoding flagellin were upregulated. While the DclpP mutant was attenuated in cell invasion, this attenuation was not present in a ΔclpP/rpoS:: amp double mutant, suggesting the repression of invasion was directed through RpoS. The expression of the csrA virulence regulator was increased in the ΔclpP mutant and decreased in the rpoS:: amp and ΔclpP/rpoS:: amp mutants, indicating that ClpP affects the csrA expression level as well. Thus, this study suggests that ClpP affects SPI1 expression and thereby virulence indirectly through its regulation of both RpoS and CsrA.

KW - Faculty of Health and Medical Sciences

KW - salmonella

KW - virulens

KW - protease

U2 - 10.1099/mic.0.065797-0

DO - 10.1099/mic.0.065797-0

M3 - Journal article

C2 - 23676436

SN - 1350-0872

VL - 159

SP - 1497

EP - 1509

JO - Microbiology

JF - Microbiology

IS - 7

ER -