Molecular & Cell Microbiology
Staff within the Group have a wide range of interests in molecular mechanisms that underlie physiological cell processes in food-relevant organisms and the interactions between food-borne pathogens and their hosts. There is specific expertise in the labelling and imaging of cells, genetic analysis of physiological processes and heterologous protein expression and purification. Specific current research themes are outlined below.
Listeria monocytogenes gene regulation
The fact that Listeria is able to grow and adapt to both the human body and low temperature environments makes it a very successful food-borne pathogen. Expression of the flagellum is temperature-regulated such that the genes are only expressed below 25°C, and motility is seen as function that aids its survival in the environment. Dr. Cath Rees and Dr. Phil Hill are investigating how the regulation of flagellin is modulated by other environmental factors and how the regulation of such survival genes and the pathogenicity genes are interconnected.
Cells visualised using fluorescent microscopy and anti-flagelin antisera.
Left: Wild type Listeria at 20°C
Right: Listeria Flagellin mutants at 20°C
Staphylococcus aureus pathogenicity
Staphylococci cause a wide variety of diseases in man and other animals and is a major concern to the food industry due to the potential to cause food poisoning. However they also cause potentially life-threatening conditions such as toxic shock syndrome and septicaemia. Staphylococci are increasingly associated with hospital acquired infection following surgery or other invasive medical procedures. The identification of novel targets for anti-staphylococcal agents or methods for prevention of infection with these bacteria is now a major priority. Dr. Phil Hill works with colleagues in the Institute of Infection and Immunity to gain a better understanding of the way staphylococci cause disease is fundamental to these processes.
GFP to track agr expression in S. aureus
Gram-negative bacterial host cell interactions
Focusing on the interactions of Escherichia coli and Campylobacter with host cells. In collaboration with colleagues at Nottingham, Professor Ian Connerton and Dr. Ken Mellits have initiated studies to address the mechanisms by which all food borne pathogens may activate signal transduction pathways in eukaryotic cells. These studies currently include enterovirulent Escherichia coli and thermophilic campylobacters. The activation of signal transduction pathways may occur simply as a consequence of infection or they may act to facilitate the course of the infection. In either event we are interested in the short and long-term effects of stimulating these pathways on the pathogen and the host. Further research focuses the synthesis and delivery pathogen products to host cells and their molecular responses and the studies of host protein interactions (Professor Ian Connerton and Dr. Phil Hill ).
Green fluorescent protein-labelled enteropathogenic E. coli infecting human colonic epithelial cells
Campylobacter jejuni and C. coli are genotypically similar organisms that cause food-borne infection worldwide. In the UK C. jejuni is responsible for 90% of the reported cases (over 40-thousand annually) with C. coli accounting for almost all the rest. It is likely these organisms enter the food chain from meat products, where C. jejuni is considered primarily a poultry coloniser and C. coli frequently colonises pigs. However, it is clear that in reality the ecological niches are not so rigid with simultaneous recovery of the two species from raw poultry products and swine carcasses. We are interested in determining the potential for genetic exchange between these species and how these possibilities relate to their ability to survive in the environment, colonise farm animals and cause human disease (Professor Ian Connerton in collaboration with Dr Gina Manning at Nottingham Trent University).
Archael transcription factors
The archaea form a distinct domain of Life ranked equally with the Bacteria and the Eukaryotes. They are single celled organisms with no internal organelles, like bacteria. However, they have information processing systems such as transcription, replication, recombination and repair apparatus that are more akin to eukaryotes. This makes them fascinating to study not only in their own right, but also as simplified model systems of the eukaryotes. Dr. David Scott works on the transcription initiation machinery of the extreme halophile Haloferax volcanii which has four TATA box binding proteins (TBPs) instead of the normal singular copy. This has revealed new and interesting mechanisms of regulation.
Yeast cell physiology
Professor Katherine Smart's research program focuses on fundamental aspects of yeast cell physiology of relevance to brewing. Current projects include (1) the role of mitochondrial DNA damage in replicative ageing in yeast, (2) understanding the biological basis for the inherent variability of fermentation lag phase and (3) the regulation of growth and division during brewery fermentation and the regulation and mechanism of brewing yeast flocculation. Other areas of research are mechanisms of sensing stress, both in general and more specifically during brewing fermentation. Current projects include: (4) ethanol and acetaldehyde stress leading to formation of mitochondrial DNA mutants (5) oxidative stress during propagation and fermentation (6) dehydration and rehydration stress damage, repair and circumvention.
Virus Host-Cell interactions
"Norwalk-like viruses" (NLVs) genomes contain three open reading frames which respectively encode the non-structural proteins (1), capsid proteins (2) and a basic protein of unknown function (3). Interestingly, open reading frames 1 and 2 share conserved sequences within their N-termini. As a first step to understand the role of these conserved sequences in NLV infection Dr. Ken Mellits has used reporter gene based assays to examine their translational efficiency.
The over-expression and purification of proteins for in vitro biochemical and biophysical studies is a core technology in our laboratory. Professor Ian Connerton and Dr. David Scott have experience of heterologoues expression of proteins from all three domains of Life and have long experience of the use bacterial and yeast expression systems. They also have a protein purification suite for the production of pure recombinant proteins. Projects include making use of the traditional benefits of biological catalysts (chemical specificity, mild reaction conditions and low environmental loads) for food applications.