Abstract
1Division of Veterinary Medical Microbiology, Research Institute Borstel, Institute for Experimental Biology and Medicine, Borstel, Federal Republic of Germany
2Institute for Microbiology, Christian-Albrechts-University, Kiel, Federal Republic of Germany
3Department of Organic Chemistry, University of Newcastle upon Tyne, Newcastle, Great Britain
4Center for Research in Biochemistry and Cell Genetics, Centre National de la Recherche Scientific, Toulouse, France