Prior to joining the University of Hertfordshire, Allan was a research scientist with ICI working on aspects of fungal physiology and plant tissue culture. His career as Senior Lecturer at the University of Hertfordshire encompassed teaching in microbiology and research in microbial physiology and fermentation technology. Allan retired from the University and continued as a Visiting Lecturer but also combined his interest in local history and microbiology in his research on the history of the brewing industry in Hertfordshire. Allan has taken an advisory role in the development of this edition but the influence he had on the previous two editions very much remains. He is a member of the Microbiology Society and was previously convener of its Teaching Group.Stephen J. Hall, MSc, PhD, Senior Lecturer at University of Hertfordshire. Stephen's career as Senior Lecturer at the University of Hertfordshire has encompassed teaching in numerous fields across the Chemical, Biological and Environmental Sciences together with research in effluent treatment, microbial physiology and fermentation technology. He is a member of the Society of Chemistry and Industry, and a Fellow of the Higher Education Academy.