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Co‐ordinate regulation of Salmonella typhimurium invasion genes by environmental and regulatory factors is mediated by control of hilA expression
Author(s) -
Bajaj Vivek,
Lucas Robin L.,
Hwang Clara,
Lee Catherine A.
Publication year - 1996
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 - 10.1046/j.1365-2958.1996.d01-1718.x
Subject(s) - biology , pathogenicity island , salmonella , microbiology and biotechnology , gene , plasmid , regulation of gene expression , regulator gene , gene expression , operon , genetics , escherichia coli , bacteria
During infection of their hosts, salmonellae enter intestinal epithelial cells. It has been proposed that when Salmonella typhimurium is present in the intestinal lumen, several environmental and regulatory conditions modulate the expression of invasion factors required for bacterial entry into host cells. We report here that the expression of six different S. typhimurium invasion genes encoded on SPI1 ( Salmonella pathogenicity island 1) is co‐ordinately regulated by oxygen, osmolarity, pH, PhoPQ, and HilA. HilA is a transcriptional activator of the OmpR/ToxR family that is also encoded on SPI1. We have found that HilA plays a central role in the co‐ordinate regulation of invasion genes by environmental and regulatory conditions. HilA can activate the expression of two invasion gene– lacZY fusions on reporter plasmids in Escherichia coli , suggesting that HilA acts directly at invasion‐gene promoters in S. typhimurium . We have found that the regulation of invasion genes by oxygen, osmolarity, pH, and PhoPQ is indirect and is mediated by regulation of hilA expression by these environmental and regulatory factors. We hypothesize that the complex and co‐ordinate regulation of invasion genes by HilA is an important feature of salmonella pathogenesis and allows salmonellae to enter intestinal epithelial cells.