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Effects of disruption of heat shock genes on susceptibility of Escherichia coli to fluoroquinolones.

Yamaguchi Y, Tomoyasu T, Takaya A, Morioka M, Yamamoto T - BMC Microbiol. (2003)

Bottom Line: The present results show that the bactericidal action of FQs is moderately affected by the DnaK and GroEL chaperones and strongly affected by the Lon protease.FQs have contributed successfully to the treatment of various bacterial infections, but their widespread use and often misuse, coupled with emerging resistance, have gradually compromised their utility.Our results suggest that agents capable of inhibiting the Lon protease have potential for combination therapy with FQs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Molecular Genetics, Graduate School of Pharmaceutical Sciences, Chiba University, Japan. Yuko@p.chiba-u.ac.jp

ABSTRACT

Background: It is well known that expression of certain bacterial genes responds rapidly to such stimuli as exposure to toxic chemicals and physical agents. It is generally believed that the proteins encoded in these genes are important for successful survival of the organism under the hostile conditions. Analogously, the proteins induced in bacterial cells exposed to antibiotics are believed to affect the organisms' susceptibility to these agents.

Results: We demonstrated that Escherichia coli cells exposed to levofloxacin (LVFX), a fluoroquinolone (FQ), induce the syntheses of heat shock proteins and RecA. To examine whether the heat shock proteins affect the bactericidal action of FQs, we constructed E. coli strains with mutations in various heat shock genes and tested their susceptibility to FQs. Mutations in dnaK, groEL, and lon increased this susceptibility; the lon mutant exhibited the greatest effects. The increased susceptibility of the lon mutant was corroborated by experiments in which the gene encoding the cell division inhibitor, SulA, was subsequently disrupted. SulA is induced by the SOS response and degraded by the Lon protease. The findings suggest that the hypersusceptibility of the lon mutant to FQs could be due to abnormally high levels of SulA protein resulting from the depletion of Lon and the continuous induction of the SOS response in the presence of FQs.

Conclusion: The present results show that the bactericidal action of FQs is moderately affected by the DnaK and GroEL chaperones and strongly affected by the Lon protease. FQs have contributed successfully to the treatment of various bacterial infections, but their widespread use and often misuse, coupled with emerging resistance, have gradually compromised their utility. Our results suggest that agents capable of inhibiting the Lon protease have potential for combination therapy with FQs.

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Related in: MedlinePlus

Levels of LVFX-resistance of E. coli gyrA, Δlon and gyrA, parC, Δlon mutants. (A), (B), (C) and (D) show the results of spot testing with the agar plates containing 0 μg/ml, 0.0125 μg/ml, 0.025 μg/ml, and 0.10 μg/ml LVFX, respectively. Bacterial strains used are as follows: a, W3110 (lon+) and CS5140 (Δlon); b, CS5086 (lon+) and CS5216 (Δlon); c, CS5217 (lon+) and CS5218 (Δlon).
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Figure 6: Levels of LVFX-resistance of E. coli gyrA, Δlon and gyrA, parC, Δlon mutants. (A), (B), (C) and (D) show the results of spot testing with the agar plates containing 0 μg/ml, 0.0125 μg/ml, 0.025 μg/ml, and 0.10 μg/ml LVFX, respectively. Bacterial strains used are as follows: a, W3110 (lon+) and CS5140 (Δlon); b, CS5086 (lon+) and CS5216 (Δlon); c, CS5217 (lon+) and CS5218 (Δlon).

Mentions: In Figure 6, strain CS5086 has a gyrA mutation (Ser83 to Leu). To construct a gyrA and parC double mutant, CS5086 was initially treated with mini F-parC1 (Gly78 to Asp, Val253 to Ile). Then the chromosomal parC gene of the resultant strain was replaced with parC::Cm by P1 transduction; lon was subsequently disrupted in both the gyrA and the gyrA, parC1 mutants. As shown in Figure 6, Δlon decreased the resistance of both gyrA and gyrA, parC1 to LVFX.


Effects of disruption of heat shock genes on susceptibility of Escherichia coli to fluoroquinolones.

Yamaguchi Y, Tomoyasu T, Takaya A, Morioka M, Yamamoto T - BMC Microbiol. (2003)

Levels of LVFX-resistance of E. coli gyrA, Δlon and gyrA, parC, Δlon mutants. (A), (B), (C) and (D) show the results of spot testing with the agar plates containing 0 μg/ml, 0.0125 μg/ml, 0.025 μg/ml, and 0.10 μg/ml LVFX, respectively. Bacterial strains used are as follows: a, W3110 (lon+) and CS5140 (Δlon); b, CS5086 (lon+) and CS5216 (Δlon); c, CS5217 (lon+) and CS5218 (Δlon).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC184496&req=5

Figure 6: Levels of LVFX-resistance of E. coli gyrA, Δlon and gyrA, parC, Δlon mutants. (A), (B), (C) and (D) show the results of spot testing with the agar plates containing 0 μg/ml, 0.0125 μg/ml, 0.025 μg/ml, and 0.10 μg/ml LVFX, respectively. Bacterial strains used are as follows: a, W3110 (lon+) and CS5140 (Δlon); b, CS5086 (lon+) and CS5216 (Δlon); c, CS5217 (lon+) and CS5218 (Δlon).
Mentions: In Figure 6, strain CS5086 has a gyrA mutation (Ser83 to Leu). To construct a gyrA and parC double mutant, CS5086 was initially treated with mini F-parC1 (Gly78 to Asp, Val253 to Ile). Then the chromosomal parC gene of the resultant strain was replaced with parC::Cm by P1 transduction; lon was subsequently disrupted in both the gyrA and the gyrA, parC1 mutants. As shown in Figure 6, Δlon decreased the resistance of both gyrA and gyrA, parC1 to LVFX.

Bottom Line: The present results show that the bactericidal action of FQs is moderately affected by the DnaK and GroEL chaperones and strongly affected by the Lon protease.FQs have contributed successfully to the treatment of various bacterial infections, but their widespread use and often misuse, coupled with emerging resistance, have gradually compromised their utility.Our results suggest that agents capable of inhibiting the Lon protease have potential for combination therapy with FQs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Molecular Genetics, Graduate School of Pharmaceutical Sciences, Chiba University, Japan. Yuko@p.chiba-u.ac.jp

ABSTRACT

Background: It is well known that expression of certain bacterial genes responds rapidly to such stimuli as exposure to toxic chemicals and physical agents. It is generally believed that the proteins encoded in these genes are important for successful survival of the organism under the hostile conditions. Analogously, the proteins induced in bacterial cells exposed to antibiotics are believed to affect the organisms' susceptibility to these agents.

Results: We demonstrated that Escherichia coli cells exposed to levofloxacin (LVFX), a fluoroquinolone (FQ), induce the syntheses of heat shock proteins and RecA. To examine whether the heat shock proteins affect the bactericidal action of FQs, we constructed E. coli strains with mutations in various heat shock genes and tested their susceptibility to FQs. Mutations in dnaK, groEL, and lon increased this susceptibility; the lon mutant exhibited the greatest effects. The increased susceptibility of the lon mutant was corroborated by experiments in which the gene encoding the cell division inhibitor, SulA, was subsequently disrupted. SulA is induced by the SOS response and degraded by the Lon protease. The findings suggest that the hypersusceptibility of the lon mutant to FQs could be due to abnormally high levels of SulA protein resulting from the depletion of Lon and the continuous induction of the SOS response in the presence of FQs.

Conclusion: The present results show that the bactericidal action of FQs is moderately affected by the DnaK and GroEL chaperones and strongly affected by the Lon protease. FQs have contributed successfully to the treatment of various bacterial infections, but their widespread use and often misuse, coupled with emerging resistance, have gradually compromised their utility. Our results suggest that agents capable of inhibiting the Lon protease have potential for combination therapy with FQs.

Show MeSH
Related in: MedlinePlus