Abstract
Non-toxigenic strains of Corynebacterium diphtheriae continue to cause disease within immunized populations. A subset of these corynebacteria carry the diphtheria toxin gene but in a cryptic form. To determine whether such strains might contribute to the re-emergence of functional toxin genes, the phages and fox mutations within three clone types were examined. fox-containing, β-related phages were isolated from two of the strain types. The third isolate appeared to harbour a defective prophage. One of the tox- phages encoded truncated, yet enzymatically-active, forms of diphtheria toxin, suggesting that it had sustained a point mutation within the latter half of its toxin gene. In contrast, the other mutant phage did not elicit the production of either a cross-reacting material or an ADP-ribosylating activity. Complementation tests employing a series of double lysogens confirmed that the mutations responsible for the non-toxigenic phenotype of all of the phages were cis dominant. Given these findings, it is reasonable to hypothesize that tox- genes can arise within human populations by either homologous recombination between two distinct tox- phages or spontaneous reversion within a single mutant allele.
Original language | English (US) |
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Pages (from-to) | 343-351 |
Number of pages | 9 |
Journal | Microbial Pathogenesis |
Volume | 22 |
Issue number | 6 |
DOIs | |
State | Published - Jun 1997 |
Funding
This work was supported by grants AI-10492 and GM-07270 from the NIH.
Keywords
- ADP-ribosylation
- Bacteriophages
- Corynebacterium diphtheriae
- Diphtheria toxin
- Non-toxigenic strains
ASJC Scopus subject areas
- Microbiology
- Infectious Diseases