J Bacteriol Virol.  2012 Mar;42(1):29-39. 10.4167/jbv.2012.42.1.29.

SmcR, the Quorum-sensing Master Regulator, Is Partially Involved in Temperature/Salinity-mediated Changes in Metalloprotease vvpE Expression in Vibrio vulnificus

• Kim CM
• Shin SH

• KMID: 1434770
• DOI: http://doi.org/10.4167/jbv.2012.42.1.29

Abstract

Vibrio vulnificus, a gram-negative halophilic marine bacterium and opportunistic human pathogen, must withstand various environmental changes, especially simultaneous changes in temperature and salinity, from 25degrees C/2.5% to 37degrees C/0.9% (SCTS) upon entering the human body. In our previous study, SCTS stimulated vvpE expression even in the background of a mutation in luxS encoding LuxS enzyme for the biosynthesis of quorum-sensing (QS) signal molecule autoinducer-2 (AI-2), suggesting that the A1-2-mediated QS system is partially involved in the SCTS-mediated change of vvpE expression. In this study, we examined the effects of the QS master regulator SmcR on SCTS-mediated changes in vvpE expression and extracellular VvpE production. SCTS stimulated V. vulnificus growth, but with no increase in maximal growth levels. The SCTS-mediated prolongation of the stationary growth phase resulted in a significant increase in growth phase-dependent smcR and vvpE expressions. A mutation in smcR seriously repressed vvpE expression, but had no significant effect on V. vulnificus growth. However, the smcR mutation only partially attenuates SCTS-mediated changes in vvpE expression. These results indicate that SCTS stimulates the expressions of smcR and vvpE by stimulating V. vulnificus growth, and that SmcR is only partially involved in SCTS-mediated changes in vvpE expression.

Keyword

Vibrio vulnificus; Temperature; Salinity; Metalloprotease; Autoinducer-2; Quorum-sensing

MeSH Terms

Human Body
Humans
Salinity
Vibrio
Vibrio vulnificus

Figure

• 

  Figure 1 Effect of a temperature and salinity change from 25℃/2.5% to 37℃/0.9% on smcR expression. After preconditioning by culturing at 25℃/2.5% overnight, the V. vulnificus RC196 strain with the PsmcR::lacZ transcriptional fusion was transferred into fresh broths and cultured at 25℃/2.5% or 37℃/0.9%. Bacterial growth (A) is expressed as the optical densities of culture aliquots at 600 nm (OD600). Accumulated β-galactosidase activity in culture aliquots is expressed in Miller units, and plotted against culture time (B) and bacterial growth (C). Means and standard deviations are of triplicate measurements.

• 

  Figure 2 Effect of smcR mutation on the regulation of vvpE expression induced by a change of temperature and salinity from 25℃/2.5% to 37℃/0.9%. After preconditioning by culturing at 25℃/2.5% overnight, the two V. vulnificus strains with PvvpE::lacZ transcriptional fusion, CMM2106 with wild-type smcR (A to C) and RC164 with mutated smcR (D to F) strains, were transferred to fresh broths and cultured at 25℃/2.5% or 37℃/0.9%. Bacterial growth (A and D) is expressed as optical densities of culture aliquots at 600 nm (OD600). Accumulated β-galactosidase activity in culture aliquots is expressed in Miller units, and plotted against culture time (B and E) and bacterial growth (C and F). Means and standard deviations are of triplicate measurements.

• 

  Figure 3 Effect of smcR mutation on the regulation of extracellular VvpE production induced by a change of temperature and salinity from 25℃/2.5% to 37℃/0.9%. After preconditioning by culturing at 25℃/2.5% overnight, the V. vulnificus M06-24/O (wild-type smcR), RC174 (with mutated smcR: SmcR-) and RC186 (with in trans complemented smcR: SmcR+) strains were transferred to fresh broths and cultured at 25℃/2.5% (open symbols) or 37℃/0.9% (filled symbols). (A) Bacterial growth is expressed as optical densities of culture aliquots at 600 nm (OD600). (B) Western blot using rabbit polyclonal anti-VvpE antibody was conducted after the electrophoresis of equal volumes of culture supernatants under denaturing conditions. A representative example of the three times-repeated experiments is shown. Arrows indicate the two forms of VvpE. (C) Quantitative analysis of the Western blot result using densitometry. Total intensity indicates the sum of the intensities of the two VvpE bands.

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