Growth curve of Streptococcus oralis

摘要

Difference between the artificial transformation in Gram-negative E. coli K-12 (gene cloning with double stranded DNA) and natural transformation in diplococcic Gram-positive Streptococcus has been ignored. The artificial transformation, an uptake of recombinant DNA (double stranded only) has been mostly used in gene-cloning experiments with Gram-negative E. coli K-12. The exact mechanism of such recombinant DNA uptake by competent E. coli K-12 cells still remains unknown. However, the natural transformation in diplococcic Streptococcus as initially reported by Dr. Griffith in 1928, has so far been limited within their two types of colonies, smooth and rough. Our data on S. oralis, S. mutans and S. pneumoniae, demonstrates that these two colony types are bacterial physiological changes (phenotypes) and therefore the uptake of exogenous donor DNA, double or single stranded, apparently has no role in such a physiological normal growth of bacteria (changes of colony types on solid blood agar medium). The growth curve of S. oralis presented in this work clearly demonstrates that there is a pre-competent phase in addition to their competent and post-competent phases of growth.