n-Hexane sensitivity of Escherichia coli due to low expression of imp/ostA encoding an 87 kDa minor protein associated with the outer membrane

Abstract

MostEscherichia colistrains are resistant to n-hexane.E. coliOST4251 is a n-hexane-sensitive strain that was constructed by transferring the n-hexane-sensitive phenotype from a n-hexane-sensitive strain by P1 transduction. OST4251 is resistant to diphenyl ether, which is less harmful than n-hexane to micro-organisms. The genetic determinant responsible for this subtle difference in the solvent resistance is mapped at 1·2 min on theE. colichromosome. Nucleotide sequence analysis showed that IS2and IS5had integrated upstream of theimp/ostAstructural gene in OST4251. The integration of IS2decreased the activity of theimp/ostApromoter. A product of the gene was identified immunologically as an 87 kDa minor protein associated with the outer membrane. Upon transformation with plasmids containing theimp/ostAgene, OST4251 produced a high level of the gene product in the membrane and acquired n-hexane resistance. Thus, the low level of promoter activity resulted in low Imp production and the n-hexane-sensitivity phenotype. It is likely that the gene product contributes to n-hexane resistance by reducing the influx of n-hexane.