TY - JOUR
T1 - Characterization of bacteriophages from fox-containing, non-toxigenic isolates of Corynebacterium diphtheriae
AU - Cianciotto, Nicholas P.
AU - Groman, Neal B.
N1 - Funding Information:
This work was supported by grants AI-10492 and GM-07270 from the NIH.
PY - 1997/6
Y1 - 1997/6
N2 - 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.
AB - 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.
KW - ADP-ribosylation
KW - Bacteriophages
KW - Corynebacterium diphtheriae
KW - Diphtheria toxin
KW - Non-toxigenic strains
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U2 - 10.1006/mpat.1996.0120
DO - 10.1006/mpat.1996.0120
M3 - Article
C2 - 9188089
AN - SCOPUS:0030610441
SN - 0882-4010
VL - 22
SP - 343
EP - 351
JO - Microbial Pathogenesis
JF - Microbial Pathogenesis
IS - 6
ER -