Accession Number:



Temperature Regulation of Shigella Virulence: Identification of Temperature-Regulated Shigella Invasion Genes by the Isolation of inv::lacZ Operon Fusions and the Characterization of the Virulence Gene Regulator virR

Descriptive Note:

Technical Report

Corporate Author:

Uniformed Services University Of The Health Sciences Bethesda United States

Personal Author(s):

Report Date:


Pagination or Media Count:



Penetration and multiplication within cells of the human colonic epithelium are hallmarks of Shigella spp. pathogenicity. A feature of Shigella spp. virulence is that it is regulated by growth temperature. Strains are phenotypically virulent when cultured at 37 deg C, but are phenotypically a virulent when cultured at 30 deg C. Temperature-regulated virulence genes involved in Shigella spp. pathogenesis and the regulator of the temperature-regulated virulence phenotype, virR, have been identified. The number of genes involved in Shigella spp. pathogenicity and the number of virulence genes that are temperature-regulated is unknown. The nature of the virulence gene regulator, virR, also remains to be determined. In these studies temperature-regulation of Shigella spp. virulence was approached from two perspectives first, from the aspect of the genes regulated in response to environmental temperature changes, and second from the aspect of the temperature dependent virulence gene repressor virR. lacZ operon fusion technology was employed to identify temperature-regulated virulence genes in Shigella flexneri serotype 2a. Four operon fusions identified in temperature-regulated invasion genes invlacZ were found to be i unable to invade HeLa cells ii located in a region of the 220 kb invasion plasmid defined as the minimal amount of DNA required for invasion and, iii controlled by virR. Western blot and Southern hybridization analysis indicated that three of the fusions were within genes mapping to regions previously identified as essential for a positive virulence phenotype. Analysis of bacterial surface proteins suggested that the genes marked by these fusions play a role in the correct surface expression of the ipaB and ipaC gene products. These genes were designated mxi membrane expression of Ipa. A fourth fusion was localized to a known inv gene, ipaB, which encodes one of the major immunogenic peptides of Shigella spp.

Subject Categories:

Distribution Statement: