Journal of General Microbiology (1970), 64,8530 Printed in Great Britain The Genetic Relatedness of Proteolytic Clostridium botulinum Strains

DNA binding and competition tests indicate that the species Clostridium botulinum is composed of three groups with only 4 to 18 % DNA homology with each other. One group includes the proteolytic C. botulinum and C. sporogenes strains. The DNA isolated from seven proteolytic C. botulinum A, B, F, and six C. sporogenes strains was 50 to 1 o o y 0 homologous to the C. botulinum ~ 6 2 DNA. Clostridium botulinum c and D strains form another group. Clostridium botulinum c 861 3 and D 8625 strains have 38 yo homology with the C. botulinum c573 strain. The last group comprises the non-proteo-lytic C. botulinum B, E, and F strains reported previously. All the C. botulinum strains tested were related to only one of the three groups and no intermediate strain was detected