Characterization of bacteriophages from fox-containing, non-toxigenic isolates of Corynebacterium diphtheriae

Nicholas P. Cianciotto*, Neal B. Groman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


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 languageEnglish (US)
Pages (from-to)343-351
Number of pages9
JournalMicrobial Pathogenesis
Issue number6
StatePublished - Jun 1997


  • ADP-ribosylation
  • Bacteriophages
  • Corynebacterium diphtheriae
  • Diphtheria toxin
  • Non-toxigenic strains

ASJC Scopus subject areas

  • Microbiology
  • Infectious Diseases


Dive into the research topics of 'Characterization of bacteriophages from fox-containing, non-toxigenic isolates of Corynebacterium diphtheriae'. Together they form a unique fingerprint.

Cite this