Limits...
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.

Show MeSH

Related in: MedlinePlus

Biofilm formation in flow cell and chemical complementation by DPD. Biofilms of WT (RN6390BG) and ΔluxS (ΔluxSG) were grown in a flow cell in 2% TSB with chloramphenicol (15 μg/ml). Biofilm integrity and GFP fluorescence were monitored at the 3rd day and the 5th day by CLSM. For chemical complementation, 3.9 nM DPD was added to the TSB medium at the beginning of the experiment. CLSM images are representative of two separate experiments and each grid square represents 20 μm (A) WT. (B) ΔluxS. (C) WT supplemented with DPD. (D) ΔluxS supplemented with DPD.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3539994&req=5

Figure 2: Biofilm formation in flow cell and chemical complementation by DPD. Biofilms of WT (RN6390BG) and ΔluxS (ΔluxSG) were grown in a flow cell in 2% TSB with chloramphenicol (15 μg/ml). Biofilm integrity and GFP fluorescence were monitored at the 3rd day and the 5th day by CLSM. For chemical complementation, 3.9 nM DPD was added to the TSB medium at the beginning of the experiment. CLSM images are representative of two separate experiments and each grid square represents 20 μm (A) WT. (B) ΔluxS. (C) WT supplemented with DPD. (D) ΔluxS supplemented with DPD.

Mentions: To further compare the different biofilm formation ability owing to luxS deletion, biofilm formation of WT and the ΔluxS strains was assessed using a flow-cell assay. After 3 days of incubation, biofilms produced by WT strain were undetectable as monitored by CLSM. In contrast, the ΔluxS strain began to form intact and rough biofilms. At the 5th day, the WT strain produced biofilms similar to that formed by the ΔluxS strain 2 days before; meanwhile, the ΔluxS strain formed thicker and stronger biofilms (Figure 2A and B). Analysis of the biofilms by COMSTAT is shown in Table 3. The ΔluxS strain exhibited significantly increased total biomass and average thickness of biofilms relative to those of the WT strain.


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 in flow cell and chemical complementation by DPD. Biofilms of WT (RN6390BG) and ΔluxS (ΔluxSG) were grown in a flow cell in 2% TSB with chloramphenicol (15 μg/ml). Biofilm integrity and GFP fluorescence were monitored at the 3rd day and the 5th day by CLSM. For chemical complementation, 3.9 nM DPD was added to the TSB medium at the beginning of the experiment. CLSM images are representative of two separate experiments and each grid square represents 20 μm (A) WT. (B) ΔluxS. (C) WT supplemented with DPD. (D) ΔluxS supplemented with DPD.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Biofilm formation in flow cell and chemical complementation by DPD. Biofilms of WT (RN6390BG) and ΔluxS (ΔluxSG) were grown in a flow cell in 2% TSB with chloramphenicol (15 μg/ml). Biofilm integrity and GFP fluorescence were monitored at the 3rd day and the 5th day by CLSM. For chemical complementation, 3.9 nM DPD was added to the TSB medium at the beginning of the experiment. CLSM images are representative of two separate experiments and each grid square represents 20 μm (A) WT. (B) ΔluxS. (C) WT supplemented with DPD. (D) ΔluxS supplemented with DPD.
Mentions: To further compare the different biofilm formation ability owing to luxS deletion, biofilm formation of WT and the ΔluxS strains was assessed using a flow-cell assay. After 3 days of incubation, biofilms produced by WT strain were undetectable as monitored by CLSM. In contrast, the ΔluxS strain began to form intact and rough biofilms. At the 5th day, the WT strain produced biofilms similar to that formed by the ΔluxS strain 2 days before; meanwhile, the ΔluxS strain formed thicker and stronger biofilms (Figure 2A and B). Analysis of the biofilms by COMSTAT is shown in Table 3. The ΔluxS strain exhibited significantly increased total biomass and average thickness of biofilms relative to those of the WT strain.

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