1Agricultural Research Council, Meat Research Institute, Langford, Bristol, BS18 7DY, United Kingdom
2Department of Bacteriology, University of Bristol, The Medical School, Bristol BS8 1TD, United Kingdom
3Deutsche Sammlung von Mikroorganismen, Gesellschaft für Biotechnologische Forschung mbH, D-3400 Göttingen, West Germany
4Department of Microbiology, Institute of Physical and Chemical Research, Wako-shi, Saitama-ken 351, Japan