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Roles for DNA supercoiling and the Fis protein in modulating expression of virulence genes during intracellular growth of Salmonella enterica serovar Typhimurium
Author(s) -
Ó Cróinín Tadhg,
Carroll Ronan K.,
Kelly Arlene,
Dorman Charles J.
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2006.05416.x
Subject(s) - biology , salmonella enterica , virulence , dna supercoil , salmonella , microbiology and biotechnology , gene , intracellular , serotype , dna , plasmid , bacteria , genetics , dna replication
Summary Adaptation of bacterial pathogens to an intracellular environment requires resetting of the expression levels of a wide range of both virulence and housekeeping genes. We investigated the possibility that changes in DNA supercoiling could modulate the expression of genes known to be important in the intracellular growth of the pathogen Salmonella enterica serovar Typhimurium. Our data show that DNA becomes relaxed when Salmonella grows in murine macrophage but not in epithelial cells, indicating that DNA supercoiling plays a role in discrimination between two types of intracellular environment. The ssrA regulatory gene within the SPI‐2 pathogenicity island that is required for survival in macrophage was found to be upregulated by DNA relaxation. This enhancement of expression also required the Fis nucleoid‐associated protein. Manipulating the level of the Fis protein modulated both the level of DNA supercoiling and ssrA transcription. We discuss a model of bacterial intracellular adaptation in which Fis and DNA supercoiling collaborate to fine‐tune virulence gene expression.