Proton motive force is not obligatory for growth of Escherichia coli

Abstract

When 50 μM carbonyl cyanide-m-chlorophenyl hydrazone (CCCP), a protonophore, was added to growth medium containing glucose at pH 7.5, Escherichia coli TK1001 (trkD1 kdpABC5) started exponential growth after 30 min; the generation time was 70 min at 37°C. Strain AS1 (acrA), another strain derived from E. coli K-12, also grew in the presence of 50 μM CCCP under the same conditions, except that the lag period was ca. 3 h. When this strain was grown in the presence of 50 μM CCCP and then transferred to fresh medium containing 50 ♂ CCCP, cells grew without any lag. Neither a membrane potential nor a pH gradient was detected in strain AS1 cells growing in the presence of CCCP. When either succinate or lactate was substituted for glucose, these strains did not grow in the presence of 50 μM CCCP. Thus, it is suggested that E. coli can grow in the absence of a proton motive force when glucose is used as an energy source at pH 7.5.