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Regulation of toxinogenesis in corynebacterium diphtheriae 1. mutations in bacterio phage beta that alter the effect of iron on toxin production



Regulation of toxinogenesis in corynebacterium diphtheriae 1. mutations in bacterio phage beta that alter the effect of iron on toxin production



Journal of Virology 37(3): 936-945



Diphtherial toxin is produced in maximal yields by C. diphtheriae C7(Btox+) only when Fe is present in growth-limiting amounts. Toxin production is markedly decreased under high-Fe conditions. The role of the bacteriophage .beta. genome in this apparent regulation of toxin production by Fe was studied. Using a passive immune hemolysis assay to detect toxin antigen production in individual plaques, rare phage mutants that were toxinogenic in high-Fe medium were identified. Lysogenic derivatives of C. diphtheriae C7 harboring such phage mutants were constructed. The lysogens were compared with wild-type strain C7(.beta.) for their ability to produce toxin in deferrated liquid medium containing varying amounts of added Fe. Quantitative tests for extracellular toxin were performed by competitive-binding radioimmunoassays. Phenotypically distinct mutant strains that produced slightly, moderately or greatly increased yields of toxin antigen under high-Fe conditions were identified. The toxin produced by the mutant lysogens was biologically active and immunochemically indistinguishable from wild-type toxin. Complementation experiments demonstrated that the phage mutation designated tox-201 had a cis-dominant effect on the expression of the toxin structural gene of phage .beta. The characteristics of the tox-201 mutation suggest that it defines a regulatory locus of phage .beta. that is involved in control of toxinogenesis by Fe in C. diphtheriae.

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Accession: 006291650

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PMID: 6785449


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