• DNA microarrays and global gene expression patterns
• Genomic indexing of Salmonella and E.coli
• Salmonella virulence gene expression during infectionLag Phase
• Salmonella Infection of Chicken oviduct (SafeHouse)
• Influence of Commensal flora, immune response and behaviour on Salmonella infection (VTRI104)
• Environmental regulation of the invasion and intracellular virulence gene programmes of Salmonella: a ppGpp dependent switch

• Regulation of Salmonella SPI1 & SPI2
• Bacterial nitrate metabolism in colonisation of the mammalian gastrointestinal tract
• Analysis of factors affecting Salmonella contamination of meat during the slaughter process (Biotracer)

• "Non genetic variation" gene expression within bacterial populations (Finished)

• Nucleoid associated proteins: DNA topology and gene expression.
• Acambis project on enterotoxigenic E.coli (Finished)

The role of 'Non-Genetic variation' in gene expression within bacterial populations and in virulence of Salmonella Typhimurium

Main researcher: Roy Bongaerts

Our knowledge of physiological and molecular functions of microbial cells is based almost exclusively on data obtained from population-based analyses of cultures.

Although this provides a useful insight into the average response of a population, it does not provide information on individual cells or subpopulations within microbial cultures. Data obtained by common methods can be misleading, especially if responses of cells are heterogeneous or if discrete subpopulations exist.

Figure 1: Single cell sort ( Nebe-von Caron et al., 2000) of Salmonella culture results in different colony morphology.

To study stress responses by microorganisms we must understand how individual cells respond and adapt to various changes in their environments.

Fundamental questions relate to whether all cells in a microbial population suffer the same consequence of an imposed stress and whether they respond in the same manner; what is the role of 'non genetic variation' (NGV) within populations and in virulence of Salmonella?

NGV is hypothesised to allow survival of a proportion of microorganisms during a sudden and non-permanent environmental change, while induction of stress response genes reflect a slower environmental change.

The aim of our study is to obtain information about the existence and frequency of NGV in virulence gene expression. This work involves the techniques of microbial flow cytometry in combination with GFP expression technology and surface structure analysis.

Figure 2: Surface detail of Salmonella cells obtained by atomic force microscopy (see www.ifr.ac.uk/spm )

• Nebe-von Caron, G., Stephens, P.J., Hewitt, C.J., Powell, J.R., and Badley L.R. (2000) J. Microbiol. Methods. 42, 97-114.