The generation of genetic diversity is a central facet of evolution by natural selection. Pathogenic and commensal bacteria provide a rich model for studying the importance of genetic diversity and it’s rate of generation. These organisms are subject to stringent and adaptable responses from their hosts as well as competition from other microbes and attack by bacteriophages. Most bacterial species adapt to, or survive, these challenges through genetic variants and as a result multiple mechanisms have evolved in these organisms to generate genetic diversity. Characterisation of these mechanisms is critical for understanding bacterial pathogenesis and the evolution/spread of novel phenotypes such as antibiotic resistance but also reveals elemental aspects of the processes of natural selection. Tandem DNA repeat tracts (microsatellites) are hypermutable and enable the rapid generation of genetic variants. My research is focused on understanding the mechanistic basis for and consequences of mutations in tandem DNA repeat tracts.


Neisseria meningitidis

Neisseria meningitidis (‘the meningococcus’) is the major causative agent of bacterial meningitis.

Neisseria Meningitidis
Neisseria Meningitidis

Meningococci are Gram –ve diplococci, which are usually found as commensals in the naso- and oropharynx of humans. The genomes of these bacteria contain a vast range of repetitive DNA with a range of known and potential functions. Tandem DNA repeat tracts are present within the promoters or reading frames of genes encoding surface structures or enzymes required for biosynthesis of surface structures. Mutations in these repeat tracts switch expression of genes ‘on’ and ‘off’, a process referred to as phase variation. These ‘phase variable’ changes in gene expression enable meningococci to escape immune responses and also impact on other phenotypes such as acquisition of iron and adhesion to host tissues. Experimental studies are being pursued using a range of in vitro models to investigate the effects on fitness of phase variation and of differences in the rate of mutation in the repeat tracts. Our recent collection of meningococcal carriage isolates has provided a new resource for investigations of natural changes in phase variable genes and the roles of other mechanisms for generation of genetic variation.


PhD projects with Neisseria meningitidis will focus on the following areas:-
• Phase variation-mediated escape of specific antibody responses
• Analysis of the functions and phase variation of iron acquisition systems
• Development of a reversible, selective assay of phase variation
• Examination of the extent of phase variable changes occurring in meningococcal genes during carriage


Campylobacter jejuni

Campylobacter Jejuni
Campylobacter Jejuni

Campylobacter jejuni is frequently responsible for cases of food-borne gasteroenteritis. This Gram –ve spiral-shaped bacterial species is normally found as commensal in the gasterointestinal tracts of birds or other animals or as an environmental contaminant. The genomes of this species contains many genes subject to phase variation due to mutations in mononucleotide repeat tracts. Our recent development of a reporter system to measure the phase variation of these genes is facilitating studies of the factors controlling the rate of switching. The setting-up of protocols for detecting phase variants and for rapid analysis of repeat tract lengths is underpinning biological studies of the fitness impact of phase variation in this species.


PhD projects with Campylobacter jejuni will focus on the following areas:-
• Identification of the determinants of phase variation rate
• Investigation of the selection of phase variants in biological assays
• Computer modelling of the impact of phase variation on population diversity


Research Links

Search PubMed at the US National Library of Medicine for this author: Dr C. Bayliss
Search Leicester Research ArchiveDr C. Bayliss
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Contact Details

Department of Genetics
University of Leicester

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Professor Jacqui Shaw

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