Virulence gene regulation inSalmonella enterica

Abstract

In order to infect a host, a microbe must be equipped with special properties known as virulence factors. Bacterial virulence factors are required to facilitate colonization, to survive under host defenses, and to permit multiplication inside the host. However, the possession of genes encoding virulence factors does not guarantee effective infection. There is considerable evidence that tight regulation of a given virulence factor is as important as the possession of the virulence factors themselves. Thus, an understanding of the regulation of virulence expression is fundamental to our comprehension of any infection process and can identify potential targets for disease prevention and therapy. We have summarized the lessons learned from experimental salmonellosis in terms of virulence regulation and hope to illustrate the differing requirements for gene and virulence expression.

Polynucleotide phosphorylase is a global regulator of virulence and persistency in Salmonella enterica

“…Recently, mutants of S. typhimurium have been isolated that show increased replication rates in cultured cells (20,35). Interestingly, two of the mutations thus identified inactivate the defined virulence gene regulators phoP͞phoQ and spvR (35), both of which participate in bacterial intracellular replication (6,7). In this context it is interesting to note that inactivation of PNPase also resulted in increased intracellular replication.…”

“…The expression of PNPase is autoregulated, as well as responding to environmental changes in E. coli (36)(37)(38). From this finding one may suggest a role for PNPase in degrading mRNAs that adapt the bacteria for host milieu, as does PhoP͞PhoQ and SpvR (6,7), and that a disturbance in such a regulation leads to altered expression of selected virulence functions, which causes altered infection pathogenesis. …”

“…Much of the knowledge of salmonellosis pathogenesis comes from work on the murine salmonellosis model (1,5), and this model has been used to define bacterial virulence factors (1,6,7). An important virulence trait of Salmonella is its ability to invade and grow within host cells, and many of the genetic determinants essential for these processes have been well characterized (8)(9)(10)(11).…”

“…Proteins involved in this process are encoded by a large cluster of genes collectively termed Salmonella pathogenicity island 1 (SPI 1). The ability to grow intracellularly, once internalized within the host cell, requires the coordinate expression of additional sets of virulence factors (6), such as SPI 2 (1,10).…”

Association of Three Plasmid-Encoded spv Genes Among Different Salmonella Serotypes Isolated from Different Origins

“…A number of central gene regulatory functions govern the life and growth of salmonellae, and these have been studied for decades [24]. Non-typhoid Salmonella strains associated with extra-intestinal infections in humans and animals carry an additional locus termed spv including five genes [5,25].…”