acid tolerance of Streptococcus gordonii

Overnight cultures of <i>Streptococcus gordonii</i> were harvested and resuspended in RPMI medium (pH 7.0) and then 50 microL (5x10⁵ cells) of bacteria were transferred to 1ml of RPMI medium (pH 3.0, 4.0, or 5.0). After 30 and 120 min of incubation at 37 °C, samples were serially diluted and plated on BHI agar.将戈登链球菌（Streptococcus gordonii）的过夜培养物收集并重悬于pH 7.0的RPMI培养基（RPMI Medium）中，随后取50微升（含5×10^5个细菌细胞）的菌液转移至1毫升pH分别为3.0、4.0或5.0的RPMI培养基内。于37℃条件下孵育30分钟和120分钟后，对样品进行连续梯度稀释并涂布于BHI琼脂（BHI Agar）平板上。