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

Most Escherichia coli strains are resistant to n-hexane. E. coli OST4251 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 the E. coli chromosome. Nucleotide sequence analysis showed that IS2 and IS5 had integrated upstream of the imp/ostA structural gene in OST4251. The integration of IS2 decreased the activity of the imp/ostA promoter. A product of the gene was identified immunologically as an 87 kDa minor protein associated with the outer membrane. Upon transformation with plasmids containing the imp/ostA gene, 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.

The Physiological Mechanisms of Desiccation Tolerance in Rhizobia

“…Amongst several of the proteins identified in rhizobia grown in treatment media were proteins regulated by sigma factor ơ E , which typically regulates genes required to combat stress in the periplasmic space of E. coli (Abe et al, 2003;Aono et al, 1994;Dartigalongue et al, 2001). The identification of these stress proteins corroborates the findings of the membrane integrity study that peat extract challenges cells of rhizobia during growth.…”

“…This protein, often referred to as Imp/OstA (increased membrane potential/organic solvent tolerance), is a minor outer membrane protein and is the product of the imp,ostA gene region (Abe et al, 2003;Aono et al, 1994).…”

The Protein-disulfide Isomerase DsbC Cooperates with SurA and DsbA in the Assembly of the Essential β-Barrel Protein LptD

“…We identified LptD as a protein whose correct folding was affected by the absence of DsbC. The synthetic phenotype of the surAdsbC mutant fits well with the identification of LptD as a DsbC substrate, because strains expressing low levels or mutated versions of LptD also are sensitive to antibiotics (28,31). Regarding the growth defect exhibited by the surAdsbC mutant at low temperatures, we propose that it results from perturbations in the lipid content of the OM caused by problems in the LPS insertion process.…”

Transcriptional Analysis of theostA/impGene Involved in Organic Solvent Sensitivity inEscherichia coli

“…Considering all these, we concluded that the n-hexane-sensitivity of OST4251 was caused by the lower production of the OstA protein. 4) Meanwhile, from the comprehensive analysis of E regulon by Dartingalongue et al, a E -dependent transcription of ostA was identified at À227 nucleotides far upstream from the initiation codon of ostA. 5) In this paper, we demonstrated identification of two new promoters responsible for the constitutive expression of ostA.…”

“…Instead, we found that IS2 was integrated at À83 bp from the initiation codon of ostA in OST4251. 4) The integration of IS2 at this position seemed to disrupt the putative promoter sequence. Western blotting analysis showed that amount of OstA protein in OST4251 was significantly decreased compared with that in JA300, supporting this idea.…”