1. School of Biology, Queens Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK
2. Present address: Institute of Microbiology, University of Sindh, Jamshoro, Pakistan.
3. Present address: Nottingham Trent University, Nottingham, NG11 8NS, UK.
4. School of Medicine, University of Nottingham, Nottingham, NG7 2UH, UK
5. Present address: Albumedix Ltd, Nottingham, NG7 1FD, UK.