FIG. 2.

Proteins differentially expressed with acetic acid or in the ackA-pta strain. The layered view superimposes two composite images representing different growth conditions. Each composite image is based on three 2-D gels from replicate cultures. All E. coli cultures were grown at 37°C to an OD₆₀₀ of 0.4 in LBK broth buffered with 50 mM MOPS and 50 mM TES, pH 6.7. (A) Strain W3110 was grown in buffered LBK broth with (pink) or without (green) 50 mM acetic acid. (B) Strain W3110 ackA-pta (pink) or W3110 (green) was grown in buffered LBK broth. In the layered views, pink and green indicate proteins induced and repressed, respectively, in the presence of acetic acid (A) or proteins constitutively induced or repressed in the ackA-pta strain (B), based on pairwise comparison of individual gels (summarized in Table 1). The horizontal axis represents the approximate pH range of the isoelectric focusing first dimension. The vertical axis represents the molecular mass in kilodaltons. Proteins in the 2-D gels were silver stained. For N-terminal sequence identification, the proteins were electroblotted and stained with Coomassie blue.