Effect of global transcriptional regulators related to carbohydrate metabolism on organic solvent tolerance in Escherichia coli

The effect of global transcriptional regulators related to carbohydrate metabolism on organic solvent tolerance (OST) in Escherichia coli has been investigated. The OSTs of the E. coli K-12 BW25113 knockout mutants acrA, acrB, cra, crp, cyaA, fnr, and mlc were investigated on the basis of colony forming efficiency on an agar plate overlaid with organic solvents. The knockout mutants of the cyclic AMP receptor protein (Δcrp) and adenylate cyclase (ΔcyaA) were found to increase their OSTs. However, their OSTs decreased to the level of the wild-type strain when the ΔcyaA cells were grown in the presence of exogenous cyclic AMP. These results indicate that the formation of the cAMP-Crp complex is related to OST. The microbial-adhesion-to-hydrocarbon test on the Δcrp and ΔcyaA mutants revealed that these mutants bound less abundantly to the organic solvent phase. In the Δcrp and ΔcyaA mutants, the expression levels of GadB and NuoG increased to the level of the wild type. The OSTs of ΔgadB and ΔnuoG mutants decreased, suggesting that the expressions of these proteins are involved in the increased OST in the Δcrp and ΔcyaA mutants.