Communication, Co-operation and Conflict in Pathogenic Bacterial Biofilms
Project Supervisor: Dr Steve Diggle
Understanding altruistic behaviours, those actions that increase another individual’s fitness at a cost to your own, is one of the greatest challenges to evolutionary biologists, as natural selection appears to favour selfish, un-co-operative individuals (cheats). However, it is only recently that social behaviour in microorganisms has been studied with respect to evolutionary theory (West et al. 2006. Nat Rev Micro 4: 597-607), and so there is strong potential to develop complementary research in this area from both molecular and adaptive (Darwinian) perspectives as bacteria exhibit remarkable social behaviours which some workers have suggested are similar to those performed by insects, vertebrates and humans. Perhaps the paradigm for bacterial co-operation and social behaviour can be seen in the diverse quorum sensing (QS) cell-cell signalling systems found in both Gram-negative and Gram-positive bacteria (see: http://www.nottingham.ac.uk/quorum). It is generally assumed that QS is co-operative and is for the benefit of the local population as a whole. However, two of the greatest problems for evolutionary biology are explaining co-operation and communication, and these both appear to come together in QS, causing a double problem.
QS has also been shown in a number of bacterial species to be important in the development of multicellular communities known as biofilms. Biofilms are ubiquitous, being found in such diverse environments as the cystic fibrosis (CF) lung, dental plaque, wounds, on rock surfaces and at the bottom of rivers. They have a definite structure, including water channels, which may involve a number of different ‘specialist’ cells (rather akin to social insect societies) and they are often enclosed by an exopolysaccharide matrix which can make them difficult to eradicate and are therefore of particular medical importance. For example, biofilm-growing cells are often significantly more resistant to antibiotics than planktonic cells, and the matrix can also help to protect bacterial cells against the host immune system during infection. Traditional approaches to eradicate biofilms have focused on understanding the molecular mechanisms governing single species biofilm growth and differentiation, and have often investigated the roles of specific genes. However, in the wild, biofilms are highly dynamic communities often involving multiple species with many social interactions, and they are full of potential for the analysis of co-operation and conflict between cells.
To date, little empirical work has been undertaken to model social evolution theory in the context of biofilms. This PhD project seeks to investigate cheating behaviour, in the context of QS, in bacterial biofilms and the consequences on the overall stability of these structures. This is important to understand as QS mutants are often isolated naturally from the sputum of CF patients. This project will provide excellent training in microbiology, molecular biology and evolutionary theory and will involve collaborative research with Professor Stuart West, Dr Andy Gardner and Dr Ashleigh Griffin at the Institute of Evolutionary Biology, University of Edinburgh (see: http://westgroup.biology.ed.ac.uk).
Students should have a first or 2i honours degree in biological sciences. A strong background in evolutionary biology is desirable.
Due to funding restrictions, this studentship, which is available from 1 October 2007, only provides funding for students from the UK/Europe.
Informal enquiries may be addressed to Dr S Diggle, Email: Steve.Diggle@Nottingham.ac.uk.
Applications, with a detailed CV and the names and addresses of two referees, should be sent to Mrs D Mitchell, Centre for Biolmolecular Sciences, School of Molecular Medical Sciences, The University of Nottingham, University Park, Nottingham, NG7 2RD. Email: Diane.Mitchell@Nottingham.ac.uk.
Reference : MED116
Closing Date : Open until filled
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