Figure 1. An example of the use of 2-DE differential display to show changes in phenotype. Cellular proteins extracted from S. gordonii grown in a chemostat were focused on IPG strips over the pI range 5.5 to 6.7 before being separated in the 2nd dimension on 12-18% acrylamide gels by SDS-PAGE. The protein circled in the inset was down-regulated as the environmental pH increased from (A) pH 6.5 to (B) pH 7.0 and (C) pH 7.5.