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Staphylococcus aureus autoinducer-2 quorum sensing decreases biofilm formation in an icaR-dependent manner.

Yu D, Zhao L, Xue T, Sun B - BMC Microbiol. (2012)

Bottom Line: Our data indicate a cumulative effect of the two QS systems on the regulation of biofilm formation in S. aureus.These findings demonstrate that AI-2 can decrease biofilm formation in S. aureus via an icaR-activation pathway.This study may provide clues for therapy in S. aureus biofilm-associated infection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Immunology, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.

ABSTRACT

Background: Staphylococcus aureus is an important pathogen that causes biofilm-associated infection in humans. Autoinducer 2 (AI-2), a quorum-sensing (QS) signal for interspecies communication, has a wide range of regulatory functions in both Gram-positive and Gram-negative bacteria, but its exact role in biofilm formation in S. aureus remains unclear.

Results: Here we demonstrate that mutation of the AI-2 synthase gene luxS in S. aureus RN6390B results in increased biofilm formation compared with the wild-type (WT) strain under static, flowing and anaerobic conditions and in a mouse model. Addition of the chemically synthesized AI-2 precursor in the luxS mutation strain (ΔluxS) restored the WT phenotype. Real-time RT-PCR analysis showed that AI-2 activated the transcription of icaR, a repressor of the ica operon, and subsequently a decreased level of icaA transcription, which was presumably the main reason why luxS mutation influences biofilm formation. Furthermore, we compared the roles of the agr-mediated QS system and the LuxS/AI-2 QS system in the regulation of biofilm formation using the ΔluxS strain, RN6911 and the Δagr ΔluxS strain. Our data indicate a cumulative effect of the two QS systems on the regulation of biofilm formation in S. aureus.

Conclusion: These findings demonstrate that AI-2 can decrease biofilm formation in S. aureus via an icaR-activation pathway. This study may provide clues for therapy in S. aureus biofilm-associated infection.

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Related in: MedlinePlus

Biofilm formation under static conditions and chemical complementation by DPD of different concentrations. Biofilm growth of S. aureus WT (RN6390B), ΔluxS and ΔluxS complemented with different concentrations of chemically synthesized DPD in 24-well plates for 4 h under aerobic conditions (A1: 0.39 nM, A2: 3.9 nM, A3: 39 nM, A4: 390 nM). The cells that adhered to the plate after staining with crystal violet were measured by OD560.
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Figure 1: Biofilm formation under static conditions and chemical complementation by DPD of different concentrations. Biofilm growth of S. aureus WT (RN6390B), ΔluxS and ΔluxS complemented with different concentrations of chemically synthesized DPD in 24-well plates for 4 h under aerobic conditions (A1: 0.39 nM, A2: 3.9 nM, A3: 39 nM, A4: 390 nM). The cells that adhered to the plate after staining with crystal violet were measured by OD560.

Mentions: Previous studies showed that biofilm formation was influenced by the LuxS/AI-2 system both in Gram-positive and Gram-negative bacteria [32,34]. The genome of S. aureus encodes a typical luxS gene, which plays a role in the regulation of capsular polysaccharide synthesis and virulence [43]. In this study, to investigate whether LuxS/AI-2 system regulates biofilm formation in S. aureus, we monitored the biofilm formation of S. aureus WT strain RN6390B and the isogenic derivative ΔluxS strain using a microtitre plate assay. As shown in Figure 1A, the WT strain formed almost no biofilm after 4 h incubation at 37°C. However, the ΔluxS strain formed strong biofilms as measured by quantitative spectrophotometric analysis based on OD560 after crystal violet staining (Figure 1A). This discrepancy could be complemented by introducing a plasmid that contains the luxS gene (Figure 1B).


Staphylococcus aureus autoinducer-2 quorum sensing decreases biofilm formation in an icaR-dependent manner.

Yu D, Zhao L, Xue T, Sun B - BMC Microbiol. (2012)

Biofilm formation under static conditions and chemical complementation by DPD of different concentrations. Biofilm growth of S. aureus WT (RN6390B), ΔluxS and ΔluxS complemented with different concentrations of chemically synthesized DPD in 24-well plates for 4 h under aerobic conditions (A1: 0.39 nM, A2: 3.9 nM, A3: 39 nM, A4: 390 nM). The cells that adhered to the plate after staining with crystal violet were measured by OD560.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3539994&req=5

Figure 1: Biofilm formation under static conditions and chemical complementation by DPD of different concentrations. Biofilm growth of S. aureus WT (RN6390B), ΔluxS and ΔluxS complemented with different concentrations of chemically synthesized DPD in 24-well plates for 4 h under aerobic conditions (A1: 0.39 nM, A2: 3.9 nM, A3: 39 nM, A4: 390 nM). The cells that adhered to the plate after staining with crystal violet were measured by OD560.
Mentions: Previous studies showed that biofilm formation was influenced by the LuxS/AI-2 system both in Gram-positive and Gram-negative bacteria [32,34]. The genome of S. aureus encodes a typical luxS gene, which plays a role in the regulation of capsular polysaccharide synthesis and virulence [43]. In this study, to investigate whether LuxS/AI-2 system regulates biofilm formation in S. aureus, we monitored the biofilm formation of S. aureus WT strain RN6390B and the isogenic derivative ΔluxS strain using a microtitre plate assay. As shown in Figure 1A, the WT strain formed almost no biofilm after 4 h incubation at 37°C. However, the ΔluxS strain formed strong biofilms as measured by quantitative spectrophotometric analysis based on OD560 after crystal violet staining (Figure 1A). This discrepancy could be complemented by introducing a plasmid that contains the luxS gene (Figure 1B).

Bottom Line: Our data indicate a cumulative effect of the two QS systems on the regulation of biofilm formation in S. aureus.These findings demonstrate that AI-2 can decrease biofilm formation in S. aureus via an icaR-activation pathway.This study may provide clues for therapy in S. aureus biofilm-associated infection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Immunology, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.

ABSTRACT

Background: Staphylococcus aureus is an important pathogen that causes biofilm-associated infection in humans. Autoinducer 2 (AI-2), a quorum-sensing (QS) signal for interspecies communication, has a wide range of regulatory functions in both Gram-positive and Gram-negative bacteria, but its exact role in biofilm formation in S. aureus remains unclear.

Results: Here we demonstrate that mutation of the AI-2 synthase gene luxS in S. aureus RN6390B results in increased biofilm formation compared with the wild-type (WT) strain under static, flowing and anaerobic conditions and in a mouse model. Addition of the chemically synthesized AI-2 precursor in the luxS mutation strain (ΔluxS) restored the WT phenotype. Real-time RT-PCR analysis showed that AI-2 activated the transcription of icaR, a repressor of the ica operon, and subsequently a decreased level of icaA transcription, which was presumably the main reason why luxS mutation influences biofilm formation. Furthermore, we compared the roles of the agr-mediated QS system and the LuxS/AI-2 QS system in the regulation of biofilm formation using the ΔluxS strain, RN6911 and the Δagr ΔluxS strain. Our data indicate a cumulative effect of the two QS systems on the regulation of biofilm formation in S. aureus.

Conclusion: These findings demonstrate that AI-2 can decrease biofilm formation in S. aureus via an icaR-activation pathway. This study may provide clues for therapy in S. aureus biofilm-associated infection.

Show MeSH
Related in: MedlinePlus