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Toxinogeny in Corynebacterium diphtheriae after loss of catalase, cystinase, or deoxyribonuclease activity
Abstract:
The relationship of catalase, cystinase, and deoxyribonuclease activity to toxinogeny in Corynebacterium diphtheriae was examined. Mutants deficient in each activity were isolated after mutagenization of strain C4 with nitrosoguanidine. All mutants were converted to toxinogeny after lysogenization with beta-converting phage, thus establishing that there is no absolute link between toxin production and these enzymatic activities. No differences were observed in the rate of lysogenization of the mutants by beta-converting phage over that of the parental strain. However, the data suggest that catalase mutants lysogenic for beta phage are generally induced at a higher rate than the parental strain after irradiation with ultraviolet light. Cystinase mutants vary widely in their rate of induction whereas the deoxyribonuclease mutants are similar to the parental strain. The relationship of these results to the production of toxinogenic strains is discussed.
Insights
Toxin production in Corynebacterium diphtheriae is not absolutely linked to catalase, cystinase, or deoxyribonuclease activity. Mutants lacking these enzymes could still produce toxin after phage infection, indicating independent genetic regulation.
Area of Science:
- Microbiology
- Molecular Biology
- Bacteriology
Background:
- Corynebacterium diphtheriae is an important human pathogen.
- Toxin production is a key virulence factor.
- The genetic and enzymatic basis of toxinogeny is not fully understood.
Purpose of the Study:
- To investigate the relationship between specific enzymatic activities and toxin production in C. diphtheriae.
- To determine if catalase, cystinase, or deoxyribonuclease activity is essential for toxinogeny.
Main Methods:
- Isolation of C. diphtheriae mutants deficient in catalase, cystinase, and deoxyribonuclease using nitrosoguanidine mutagenesis.
- Lysogenization of mutant strains with beta-converting phage to assess toxin production.
- Evaluation of phage induction rates after UV irradiation in mutant strains.
Main Results:
- All enzymatic mutants were converted to toxinogeny after lysogenization, demonstrating no absolute requirement for these enzymes in toxin production.
- Catalase-deficient mutants showed a higher induction rate of beta phage after UV irradiation compared to the wild-type.
- Cystinase mutants exhibited variable induction rates, while deoxyribonuclease mutants showed induction rates similar to the wild-type.
Conclusions:
- Catalase, cystinase, and deoxyribonuclease activities are not prerequisites for toxin production in Corynebacterium diphtheriae.
- Catalase deficiency may influence the induction of lysogenic phages, potentially impacting toxin gene expression.
- The study clarifies the independent nature of these enzymatic activities from toxinogeny.
