查看文章

Using 21 species of oral bacteria, representing six acidogenic genera, we undertook to determine whether the pH‐limiting exponential growth is related to the ability of the organisms to generate an acid‐tolerance response that results in enhanced survival at low pH. The lower pH limit of exponential growth varied by more than two units with that of Neisseria A182 at pH 6.34; growth of Lacto‐bacillus casel RB1014 stopped at pH 3.81, with species of Actinomyces, Enter ococcus, Prevotella and Streptococcus falling between these limits. The working hypothesis was that the organisms with the higher pH limits for growth are unable to respond to acidic environments in order to survive, whereas the more aciduric organisms would possess or acquire acid tolerance. Adaptation to acid tolerance was tested by determining whether the prior exposure of exponential‐phase cells to a low, sub‐lethal pH would trigger the …