The effect of growth rate on the adhesion of the oral bacteria Streptococcus mutans and Streptococcus milleri

As a preliminary to measuring the hydrophobicity of continuous-culture cells, batch-grown cells of a number of Streptococcus mutans strains were tested for their ability to adhere to hexadecane. The hydrophobic properties of such cells were markedly affected by experimental variables such as the composition of the growth medium and the buffer in which the cells were subsequently suspended. For example, the replacement of glucose by fructose in a chemically-defined growth medium (CDM) increased cell hydrophobicity. Strep. mutans B13 and Streptococcus milleri B448 were separately grown glucoselimited in the CDM at various dilution rates from D = 0.04 h −1 to D = 0.7 h ∮1, corresponding to mean generation times of 17 and 1 h. Slow-growing cells of both strains were more hydrophobic than fast-growing cells, which, in conjunction with previous studies, supports the suggestion that hydrophobic bonding may play a role in bacterial adherence.