Archives of Microbiology

, Volume 154, Issue 5, pp 443–447 | Cite as

Repression of toxin production by tryptophan in Clostridium botulinum type E

  • Gregory J. Leyer
  • Eric A. Johnson
Original Papers


Of the seven amino acids required by Clostridium botulinum type E, tryptophan is the most essential and may provide the cell with nitrogen. The addition of excess tryptophan (10–20 mM) or other nitrogenous nutrients to minimal growth medium markedly decreased toxin formation but did not affect growth in C. botulinum type E. On the other hand, the addition of an enzymatic digest of casein (NZ Case) stimulated toxin formation and overcame repression by tryptophan. Immunoblots of proteins in culture fluids using antibodies to type E toxin indicated that tryptophan-repressed cultures produced less neurotoxin protein. Inhibitors of neurotoxin did not accumulate in cultures grown in minimal medium supplemented with high tryptophan. The results suggest that tryptophan availability in foods or in the intestine may be important for toxin formation by C. botulinum type E.

Key words

Clostridium botulinum type E Tryptophan metabolism Nitrogen repression Botulinum neurotoxin formation 


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Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • Gregory J. Leyer
    • 1
  • Eric A. Johnson
    • 1
  1. 1.Department of Food Microbiology and ToxicologyUniversity of WisconsinMadisonUSA

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