New Role of small RNAs in Salmonella Infections Uncovered
Published:30 Jan.2023 Source:Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign
Salmonella are food-borne pathogens that infect millions of people a year. To do so, these bacteria depend on a complex network of genes and gene products that allow them to sense environmental conditions. In a new paper, researchers have investigated the role of small RNAs that help Salmonella express their virulence genes.
The bacteria infect humans by first invading the cells of the intestine using a needle-like structure, called a type 3 secretion system. This structure injects proteins directly into the cells, setting off a cascade of changes that cause inflammation, and ultimately cause diarrhea. The genes that encode this system, and other genes that are needed for invasion, are found on a region of DNA known as the Salmonella pathogenicity island 1.
"SPI-1 needs to be well controlled," said Sabrina Abdulla, a graduate student in the Vanderpool lab, and the first author of the study. "If the type 3 secretion system needle apparatus is not made, Salmonella cannot cause an infection, and if too much of the needle apparatus is made, it makes Salmonella sick."
SPI-1 is controlled by an extensive regulatory network. First, three transcription factors: HilD, HilC, and RtsA, all control their own and each other's DNA expression. They also activate another transcription factor, HilA, which activates the rest of the SPI-1 genes. If this isn't complicated enough, SPI-1 also needs to sense a variety of environmental cues and tune the expression of its genes in order to infect its host.