1. Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, Pretoria 0007, South Africa
2. School of Chemistry, The University of Manchester, Manchester, M13 9PL, UK
3. The Manchester Institute of Biotechnology, The University of Manchester, Manchester, M1 7DN, UK
4. Centre for Synthetic Biology of Fine and Speciality Chemicals, The University of Manchester, Manchester, M1 7DN, UK