Role of SdiA in Salmonella enterica serovar Typhimurium physiology and virulence

Abstract

sdiAin Salmonella enterica serovar Typhimurium encodes a protein belonging to the LuxR family of transcriptional regulators. Initial computer analysis revealed the presence of a fur box 19 bp upstream of the start codon of the sdiA gene and a helix-turn-helix motif in the carboxy-terminal part of the SdiA protein typical for transcriptional regulators. Deletion of the furbox resulted in twofold increase of sdiA transcription. Furthermore, addition of dipyridyl, an iron chelator, to culture media increased sdiA transcription to the level observed in the fur box mutant, confirming that sdiA is suppressed in the presence of iron. When S. entericasv. Typhimurium was grown in conditioned medium, sdiA transcription was repressed to 30% of that in cells grown in fresh LB broth; this repression was independent of the fur box. Oral infection of mice with the strain lacking the helix-turn-helix domain of SdiA indicated increased virulence of this S. entericasv. Typhimurium mutant. sdiA, dually controlled by iron concentration and culture-density-derived signals, may therefore play an important role in S. entericasv. Typhimurium virulence regulation.

Identification of Escherichia coli O157 : H7 genes influencing colonization of the bovine gastrointestinal tract using signature-tagged mutagenesis

“…SdiA negatively regulates the expression of EspD and intimin in E. coli O157 : H7 (Kanamaru et al, 2000), and one might have anticipated that upregulation of LEE expression caused by mutation of sdiA would enhance the carriage and virulence of EHEC. Mutation of sdiA has been reported to increase the virulence of Salmonella enterica serovar Typhimurium following oral inoculation of mice (Volf et al, 2002). However, the observed defect in E. coli O157 : H7 carriage caused by mutation of sdiA may be explained by positive regulation of other colonization factors.…”

RNA Sequencing Reveals Differences between the Global Transcriptomes of Salmonella enterica Serovar Enteritidis Strains with High and Low Pathogenicities

“…Similarly, when S. Typhimurium is grown in motility medium, sdiA regulates expression of virulence plasmid-associated genes (89). Interestingly, sdiA is also dually controlled by iron concentration and culture density-derived signals, and the deletion of the helix-turnhelix (HTH) domain of sdiA results in increased virulence of S. Typhimurium in a murine model of infection (90), suggesting that sdiA contributes to diverse genetic effects with possible links to motility, bacterial cell septation, response to DNA-damaging agents, and virulence. Similar to sdiA, ecnR is linked to motility because it negatively regulates flhDC transcription and affects bacterial motility; however, the role of ydcI and SEN4085 in S. Enteritidis has not been established.…”

Vaccination and early protection against non-host-specific Salmonella serotypes in poultry: exploitation of innate immunity and microbial activity

“…Studies conducted to elucidate the mechanism of bacteriological competition between Salmonella strains have been inconclusive. An initial hypothesis that the inhibition both in vitro and in vivo was the result of quorum sensing to suppress growth prior to starvation was not supported by mutational studies [157,158]. This idea was stimulated by experiments in which the two strains were separated in vitro by a dialysis membrane such that physical separation was possible whilst still allowing diffusion of small molecules.…”

“…An association with quorum sensing might have been strengthened by a link with genes known to be associated with this phenomenon, but mutations in luxS [161,162] and sdiA [163,164], known to be involved in this process in E. coli had no effect on inhibition [157]. The in vitro system involving inhibition by stationary-phase broth nutrient cultures of a freshly added strain is microbiologically very interesting and has practical value in explaining, at least in part, the in vivo phenomenon [157,158,160]. Despite the fact that the nature of the inhibitory action between two strains is not yet fully elucidated, it is clear that such interactions between Salmonella strains do play a role in colonization-inhibition in vivo.…”