Cultures of a variety of pneumococcal strains maintained competence longer and gave higher yields of transformants when incubated in M1 medium compared with NS medium. This was most probably due to the cells remaining competent for longer in M1 medium. Various parameters controlling the development of competence in M1 medium were investigated. The onset of competence was delayed in M1 medium compared with that in NS medium, probably due to the presence of Casamino acids in the former. Competence developed normally over a pH range of 7.3 to 8.3, with cultures inoculated from the same batch of frozen ‘precultures’ showing consistent characteristics. This was not observed when frozen ‘sensitization’ cultures were revived.

The average cell chain length increased with the development of competence in all the strains tested and, with the exception of cultures which had entered the stationary growth phase, declined after the culture had lost its competence. The extent of the increase in chain length was dependent upon the pH of the medium.


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