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Overexpression of luxS cannot increase autoinducer-2 production, only affect the growth and biofilm formation in Streptococcus suis.

Wang Y, Yi L, Zhang Z, Fan H, Cheng X, Lu C - ScientificWorldJournal (2013)

Bottom Line: In our previous study, the function of LuxS in AI-2 production was verified in Streptococcus suis (SS).An SS strain that overexpressed luxS was constructed to comprehensively understand the function of AI-2.Thus, AI-2 production is not correlated with luxS transcription. luxS expression is constitutive, but the transcription of pfs is perhaps correlated with AI-2 production in SS.

View Article: PubMed Central - PubMed

Affiliation: College of Animal Science and Technology, Henan University of Science and Technology, Luoyang 471003, China ; Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China ; OIE Reference Laboratory for Swine Streptococcosis, Nanjing 210095, China.

ABSTRACT
LuxS/AI-2 quorum sensing (QS) system involves the production of cell signaling molecules via luxS-based autoinducer-2 (AI-2). LuxS has been reported to plays critical roles in regulating various behaviors of bacteria. AI-2 is a byproduct of the catabolism of S-adenosylhomocysteine (SAH) performed by the LuxS and Pfs enzymes. In our previous study, the function of LuxS in AI-2 production was verified in Streptococcus suis (SS). Decreased levels of SS biofilm formation and host-cell adherence as well as an inability to produce AI-2 were observed in bacteria having a luxS mutant gene. In this study, the level of AI-2 activity exhibits a growth-phase dependence with a maximum in late exponential culture in SS. An SS strain that overexpressed luxS was constructed to comprehensively understand the function of AI-2. Overexpressed luxS was not able to increase the level of pfs expression and produce additional AI-2, and the bacteria were slower growing and produced only slightly more biofilm than the wild type. Thus, AI-2 production is not correlated with luxS transcription. luxS expression is constitutive, but the transcription of pfs is perhaps correlated with AI-2 production in SS.

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Related in: MedlinePlus

Production of AI-2 activity of the different strains. AI-2 activity of cell-free culture fluids in the stationary exponential phase was measured using the V. harveyi bioluminescence assay. AI-2 activity determination is expressed as relative light units and compared with the level of luminescence produced by the positive control (V. harveyi BB120). AI-2 activity of V. harveyi BB120 was set to 100% activity for normalization. V. harveyi BB120 served as a positive control and sterile THB medium as a negative control. HA9801, ΔluxS, CΔluxS, and luxS+ refer to the WT strain, the luxS mutant strain, the complementation strain, and the overexpression strain. Values are means from three independent experiments. Error bars indicate standard deviations (P < 0.05).
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fig3: Production of AI-2 activity of the different strains. AI-2 activity of cell-free culture fluids in the stationary exponential phase was measured using the V. harveyi bioluminescence assay. AI-2 activity determination is expressed as relative light units and compared with the level of luminescence produced by the positive control (V. harveyi BB120). AI-2 activity of V. harveyi BB120 was set to 100% activity for normalization. V. harveyi BB120 served as a positive control and sterile THB medium as a negative control. HA9801, ΔluxS, CΔluxS, and luxS+ refer to the WT strain, the luxS mutant strain, the complementation strain, and the overexpression strain. Values are means from three independent experiments. Error bars indicate standard deviations (P < 0.05).

Mentions: To analyze the effect of AI-2 signaling in SS, we created a ΔluxS mutant strain, a complementation strain, and an overexpression strain (luxS+) in SS HA9801. In the late exponential to the stationary exponential phase, the SS culture supernatant had the largest AI-2 luminescence response (Figure 2). The culture supernatant from the ΔluxS mutant strain induced a luminescence signal that was comparable to the signal from the negative control, which was much lower than that of the WT strain. However, the complementation strain restored AI-2 to the level of the WT strain. The overexpression strain (luxS+) generated similar levels of bioluminescence as the WT strain HA9801 (Figure 3).


Overexpression of luxS cannot increase autoinducer-2 production, only affect the growth and biofilm formation in Streptococcus suis.

Wang Y, Yi L, Zhang Z, Fan H, Cheng X, Lu C - ScientificWorldJournal (2013)

Production of AI-2 activity of the different strains. AI-2 activity of cell-free culture fluids in the stationary exponential phase was measured using the V. harveyi bioluminescence assay. AI-2 activity determination is expressed as relative light units and compared with the level of luminescence produced by the positive control (V. harveyi BB120). AI-2 activity of V. harveyi BB120 was set to 100% activity for normalization. V. harveyi BB120 served as a positive control and sterile THB medium as a negative control. HA9801, ΔluxS, CΔluxS, and luxS+ refer to the WT strain, the luxS mutant strain, the complementation strain, and the overexpression strain. Values are means from three independent experiments. Error bars indicate standard deviations (P < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3842066&req=5

fig3: Production of AI-2 activity of the different strains. AI-2 activity of cell-free culture fluids in the stationary exponential phase was measured using the V. harveyi bioluminescence assay. AI-2 activity determination is expressed as relative light units and compared with the level of luminescence produced by the positive control (V. harveyi BB120). AI-2 activity of V. harveyi BB120 was set to 100% activity for normalization. V. harveyi BB120 served as a positive control and sterile THB medium as a negative control. HA9801, ΔluxS, CΔluxS, and luxS+ refer to the WT strain, the luxS mutant strain, the complementation strain, and the overexpression strain. Values are means from three independent experiments. Error bars indicate standard deviations (P < 0.05).
Mentions: To analyze the effect of AI-2 signaling in SS, we created a ΔluxS mutant strain, a complementation strain, and an overexpression strain (luxS+) in SS HA9801. In the late exponential to the stationary exponential phase, the SS culture supernatant had the largest AI-2 luminescence response (Figure 2). The culture supernatant from the ΔluxS mutant strain induced a luminescence signal that was comparable to the signal from the negative control, which was much lower than that of the WT strain. However, the complementation strain restored AI-2 to the level of the WT strain. The overexpression strain (luxS+) generated similar levels of bioluminescence as the WT strain HA9801 (Figure 3).

Bottom Line: In our previous study, the function of LuxS in AI-2 production was verified in Streptococcus suis (SS).An SS strain that overexpressed luxS was constructed to comprehensively understand the function of AI-2.Thus, AI-2 production is not correlated with luxS transcription. luxS expression is constitutive, but the transcription of pfs is perhaps correlated with AI-2 production in SS.

View Article: PubMed Central - PubMed

Affiliation: College of Animal Science and Technology, Henan University of Science and Technology, Luoyang 471003, China ; Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China ; OIE Reference Laboratory for Swine Streptococcosis, Nanjing 210095, China.

ABSTRACT
LuxS/AI-2 quorum sensing (QS) system involves the production of cell signaling molecules via luxS-based autoinducer-2 (AI-2). LuxS has been reported to plays critical roles in regulating various behaviors of bacteria. AI-2 is a byproduct of the catabolism of S-adenosylhomocysteine (SAH) performed by the LuxS and Pfs enzymes. In our previous study, the function of LuxS in AI-2 production was verified in Streptococcus suis (SS). Decreased levels of SS biofilm formation and host-cell adherence as well as an inability to produce AI-2 were observed in bacteria having a luxS mutant gene. In this study, the level of AI-2 activity exhibits a growth-phase dependence with a maximum in late exponential culture in SS. An SS strain that overexpressed luxS was constructed to comprehensively understand the function of AI-2. Overexpressed luxS was not able to increase the level of pfs expression and produce additional AI-2, and the bacteria were slower growing and produced only slightly more biofilm than the wild type. Thus, AI-2 production is not correlated with luxS transcription. luxS expression is constitutive, but the transcription of pfs is perhaps correlated with AI-2 production in SS.

Show MeSH
Related in: MedlinePlus