RECIPROCAL CAPSULAR TRANSFORMATIONS OF PNEUMOCOCCI

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Abstract
Encapsulated pneumococci are generally transformable. A strain which acquired a capsule by transformation can be restored to the capsule-deficient condition by reverse transformation. The genetic determinant acquired by the unencapsulated transformant is identical to the mutant marker present in the unencapsulated donor strain. Spontaneous mutations resulting in impaired capsule synthesis are common. Many of these are genetically dissimilar, since recombination can restore normal capsule synthesis following interaction between a recipient strain bearing a mutation and exogenous deoxyribonucleic acid from a strain bearing a different mutation. Strains can be produced with 2 mutant markers causing different degrees of capsule impairment. Such strains can be restored to either partial or normal capsule Synthesis apparently in one step, by reaction with transforming DNA from other capsule-deficient strains.