Clostridium botulinum neurotoxin.

Laboratory methods in anaerobic bacteriology : NCDC laboratory manual

Bacterial taxonomy is the science that makes logical and rational communication possible among all scientists, microbiologists, physicians, biochemists, and others; indeed, all people who need to know and use microbiological information. Combining, as it does, the arts of classification and identification with stringent rules of nomenclature, there is much that remains subjective in the selection of limits allowed in defining each taxon. However, with the explosion of information that is accumulating regarding the chemical and genetic composition of bacterial cells, it is now becoming possible to approach the definition of limits so as to include in a taxon, at the level of either genus or species, only organisms that are truly closely related.

Taxonomy and Phylogeny

These studies show that Clostridium botulinum types C and D cultures can be cured of their prophages and converted to either type C or D depending on the specific phage used. Strains of types C and D were cured of their prophages and simultaneously ceased to produce their dominant toxins designated as C1 and D, respectively. Cured nontoxigenic cultures derived from type C strain 162 were sensitive to the phages from the toxigenic type C strain 162 and type D strain South African. When cured nontoxigenic cultures derived from strain 162 were infected with the tox+ phages from the 162 strain of type C and the South African strain of type D, they then produced toxin neutralized by types C and D antisera, respectively. Cured nontoxigenic cultures isolated from the type D South African strain were only sensitive to the parent phage, and, when reinfected with the tox+ phage, they produced toxin neutralized by type D antiserum. Type C strain 153 and type D strain 1873, when cured of their respective prophages, also ceased to produce toxins C1 and D, but, unlike strain 162 and the South African strain, they continued to produce a toxin designated as C2. When the cured cultures from strains 153 and 1873 were infected with the tox+ phage from type D strain 1873, the cultures simultaneously produced toxin that was neutralized by type D antiserum. When these cured cultures were infected with the tox+ phage from type C strain 153, the cultures produced toxin that was neutralized by type C antiserum. These studies with the four strains of C. botulinum confirm that the toxigenicity of types C and D strains requires the continued participation of tox+ phages. Evidence is presented that types C and D cultures may arise from a common nontoxigenic strain.

Interconversion of Type C and D Strains of Clostridium botulinum by Specific Bacteriophages

Tetanus and botulinum neurotoxins (TeNTand BoNT, respectively) are produced exclusively by bacterial species belonging to the genus Clostridium. Their extreme potency to man and his animals has ensured their extensive analysis by the scientific community. In recent years these studies have been strengthened by the application of recombinant procedures. As a result the genes encoding TeNT and all seven BoNT serotypes have been cloned and their entire nucleotide sequences determined. This in turn has led to significant advances in our understanding of the relationships between clostridial neurotoxins and their mode of action. The availability of these genes has also provided the starting point from which the molecular basis of bacterial toxin production may be unravelled.

Molecular Genetics of Clostridial Neurotoxins

Temperate bacteriophages of diverse morphology were demonstrated by electron microscopy in toxigenic cultures of Clostridium botulinum. The 41 strains examined included 23 type E and multiple representatives of all other types. Cultures induced with mitomycin-C generally gave better yields, but phages were also demonstrable in untreated cultures.A provisional grouping of toxigenic types into four categories is suggested, based mainly upon associated phage patterns. Group 1 comprises types A, B, and F (all proteolytic), many of whose cultures showed an icosahedral contractile phage; others contained a "bullrushy" phage with elongated head and long flexible tail; some strains yielded both. Group 2, types B and F (non-proteolytic), were associated with icosahedral contractile phages; the latter also had an octahedral flexible phage. Group 3, types C and D, yielded conspicuously large phages with octahedral heads and very long sheathed tails. One type C strain produced a long-tailed icosahedral phage. Type E ...

Eva Chang

Papers

Bacteriophages of Clostridium botulinum