About the Project
Abstract: There is growing concern about environmental reservoirs of pathogens that can cause outbreaks in human animal populations, but direct field studies remain limited by technical difficulties. In particular, while next-generation sequencing methods have started to detect very diverse mechanisms of virulence and antimicrobial resistance in soil-dwelling bacterial communities, very little is known about the ecological dynamics and the selective pressure encountered by these bacteria. We have recently started to tackle this issue using the free-living nematode Caenorhabditis elegans, which acts as both a predator and a host for multiple bacteria, including opportunistic pathogens such as Salmonella and Pseudomonas species. We have developed experimental assays to measure the effects of different bacterial strains on the fitness and population dynamics of the nematodes, as well as the growth and transmission of the bacteria. The leading hypothesis that this project will aim to test is that nematode colonisation and transmission can be adaptive strategies for pathogenic bacteria to spread in the environment. Experimental evolution will be used to measure selective pressures and identify key genetic factors, with a specific focus on Salmonella enterica and Pseudomonas aeruginosa. An important goal will be to determine the potential impact of these selective pressures for public health, in particular with respect to virulence, host specificity and antimicrobial resistance.
The project will be mainly lab-based, with opportunities to develop mathematical models for bacterial evolution as well as field surveys to sample bacteria and nematodes from agricultural settings. The project's main supervisor, Dr Restif, has many years of expertise in evolutionary biology, microbiology and mathematical modelling. Initial training in the laboratory will be provided by Dr Anaid Diaz.
Learning outcomes: the students will use a wide range of experimental techniques, including manipulation of nematodes, bacterial culture, sequencing. In addition, the design and interpretation of experiments will require the use of evolutionary theory. Applicants should have prior experience in experimental microbiology, and some training in evolutionary biology. Complementary training, especially in relevant statistical and computational techniques, will be provided in house by local experts.
Key words: experimental evolution, foodborne pathogens, virulence, transmission.
To be considered by the Department you will need to submit an official application using the online GRADSAF system (details here: http://www.graduate.study.cam.ac.uk/how-do-i-apply), for which there is a £50 fee. Please contact the supervisor before applying.
References
Relevant publications:
- Diaz SA and O Restif 2014. Spread and transmission of bacterial pathogens in experimental nematode populations of Caenorhabditis elegans. Applied and Environmental Ecology 80:5411-8.
- Martinez 2012. Bacterial pathogens: from natural ecosystems to human hosts. Environmental Microbiology 15:325-333.
- Jousset 2012. Ecological and evolutive implications of bacterial defences against predators. Environmental Microbiology 14:1830-1843.