Integration efficiencies of spontaneous mutant alleles of amiA locus in pneumococcal transformation

The distribution of integration efficiencies of independent mutations spontaneously occurring in the amiA locus was determined in two strains of pneumococcus. Strain Cl(3) integrates genetic markers with different efficiencies during transformation, whereas strain 401, isogenic with strain Cl(3), does not discriminate between markers and integrates all markers with the same high efficiency. The discriminating strain Cl(3) gives rise to spontaneous mutations in the locus amiA, which fall into four classes with respect to their individual integration efficiencies. Mutations with a low efficiency of integration are equal in number to mutations with a high efficiency. Mutations from the two other classes corresponding to intermediate and very high efficiencies are about five times less frequent. The same four classes were also found among amiA mutants spontaneously occurring in strain 401. However, the two distributions of integration efficiencies of amiA mutants arisen either in strain...