Marker Effects in Pneumococcal Transformation

  • Jean-Gérard Tiraby
  • Maurice S. Fox


Genetic markers may be transferred from one pneumococcal strain to another as the result of exposure of competent recipient bacteria to double-stranded DNA isolated from donor bacteria. Several investigators have shown that markers representing single-site mutations can be divided into several classes according to the frequency with which those markers are represented among transformants. These mutations appear to fall into four classes, the distribution of which varies according to the loci analyzed (Lacks, 1966; Sirotnak and Hachtel, 1969; Tiraby and Sicard, 1973a). The two predominant classes of markers are those that yield a high frequency of transformants (HE, for high efficiency of integration) and those that yield a low frequency of transformants (LE, for an efficiency of integration about tenfold lower) (Ephrussi-Taylor et al., 1965; Ephrussi-Taylor and Gray, 1966). When a large number of spontaneous mutations within a given locus are analyzed, two more classes are observed, one corresponding to markers with a very high efficiency of integration (from 1.5- to 2-fold more efficient than HE markers) (VHE) and the other corresponding to markers with an intermediate efficiency (IE). VHE markers are about 20 times more efficient than LE markers.


Replication Fork Integration Efficiency Pneumococcal Strain Endonucleolytic Cleavage Double Transformants 
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Copyright information

© Plenum Press, New York 1974

Authors and Affiliations

  • Jean-Gérard Tiraby
    • 1
  • Maurice S. Fox
    • 1
  1. 1.Department of BiologyMassachusetts Institute of TechnologyCambridgeUSA

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