Related Experiment Video
Updated: Jun 12, 2026

Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria
Published on: September 16, 2013
Phase variation controls expression of Salmonella lipopolysaccharide modification genes by a DNA
S E Broadbent1, M R Davies, M W van der Woude
1Centre for Immunology and Infection, Hull York Medical School and the Department of Biology, University of York, York, UK.
Abstract:
The O-antigen of Salmonella lipopolysaccharide is a major antigenic determinant and its chemical composition forms the basis for Salmonella serotyping. Modifications of the O-antigen that can affect the serotype include those carried out by the products of glycosyltransferase operons (gtr), which are present on specific Salmonella and phage genomes. Here we show that expression of the gtr genes encoded by phage P22 that confers the O1 serotype is under the control of phase variation. This phase variation occurs by a novel epigenetic mechanism requiring OxyR in conjunction with the DNA methyltransferase Dam. OxyR is an activator or a repressor of the system depending on which of its two binding sites in the gtr regulatory region is occupied. Binding is decreased by methylation at Dam target sequences in either site, and this confers heritability of the expression state to the system. Most Salmonella gtr operons share the key regulatory elements that are identified here as essential for this epigenetic phase variation.
More Related Videos
13:48Discovering CsgD Regulatory Targets in Salmonella Biofilm Using Chromatin Immunoprecipitation and High-Throughput Sequencing (ChIP-seq)
Published on: January 18, 2020
06:30A Non-Coding Small RNA MicC Contributes to Virulence in Outer Membrane Proteins in Salmonella Enteritidis
Published on: January 27, 2021
Related Concept Videos
Regulation of Bacterial Virulence
Formation of Lipopolysaccharides
Coordination of Gene Expression Processes in Bacteria
Translational Regulation
Stringent Response in E. coli
Gene Regulation in Microbial Communities: Quorum Sensing