title: Improvement of organic solvent tolerance by disruption of the lon gene in Escherichia coli.
abstract: The Lon ATP-dependent protease plays an important role in regulating many biological processes in bacteria. In this study, we examined the organic solvent tolerance of a Δlon mutant of Escherichia coli K-12 and found that the mutant showed remarkably higher organic solvent tolerance than the parent strain. Δlon mutants are known to overproduce capsular polysaccharide, resulting in the formation of mucoid colonies. We considered that this increase in capsular polysaccharide production might be involved in the organic solvent tolerance in E. coli. However, a ΔlonΔwcaJ double-gene mutant displaying a nonmucoid phenotype was as tolerant to organic solvents as the Δlon mutant, suggesting that capsular polysaccharide is not involved in organic solvent tolerance. On the other hand, the Lon protease is known to exhibit proteolytic activity against the transcriptional activators MarA and SoxS, which can enhance the expression level of the AcrAB-TolC efflux pump. We found that the Δlon mutant showed a higher expression level of AcrB than the parent strain. In addition, the ΔlonΔacrB double-gene mutant showed a significant decrease in organic solvent tolerance. Thus, it was shown that organic solvent tolerance in the Δlon mutant depends on the AcrAB-TolC pump but not capsular polysaccharide. E. coli strain JA300 acrRIS marR overexpresses the AcrAB-TolC pump and exhibits high-level solvent tolerance. In an attempt to further improve the solvent tolerance of JA300 acrRIS marR, a lon gene disruptant of this strain was constructed. However, the resulting mutant JA300 acrRIS marR Δlon showed lower solvent tolerance than JA300 acrRIS marR.
authors.affiliation: Graduate School of Interdisciplinary New Science, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585, Japan; Bio-Nano Electronic Research Center, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585, Japan.
authors.forename: Rei
authors.initials: R
authors.lastname: Watanabe
authors.affiliation: Graduate School of Interdisciplinary New Science, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585, Japan; Bio-Nano Electronic Research Center, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585, Japan; Department of Life Science, Toyo University, 1-1-1 Izumino, Itakura-machi, Gunma 374-0193, Japan. Electronic address: dokyu@toyo.jp.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Doukyu
mesh_terms: D020001:1-Butanol / Q000494:pharmacology; D000222:Adaptation, Physiological; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003510:Cyclohexanes / Q000494:pharmacology; D048168:Escherichia coli K12 / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000235:genetics; D049070:Protease La / Q000235:genetics*; D012997:Solvents / Q000494:pharmacology; D013312:Stress, Physiological
chemical_list: D020001:1-Butanol; D000900:Anti-Bacterial Agents; D003510:Cyclohexanes; D029968:Escherichia coli Proteins; D000431:Ethanol; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D017856:Phosphotransferases (Phosphate Group Acceptor); D049070:Protease La; D012997:Solvents; C083496:AcrB protein, E coli; C506365:Cyclohexane; C573281:WcaJ protein, E coli; C483567:Lon protein, E coli
keywords: AcrAB-TolC; Capsular polysaccharide; Efflux pump; Escherichia coli; Organic solvent tolerance; lon