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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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Additive effect played by the LuxS/AI-2 QS system and the agr-mediated QS system. (A) The ΔagrΔluxSG and RN6911G grew biofilms in the flow cell, and the representative images were measured by CLSM at the 3rd and 5th day of biofilm formation. Strains are indicated in the figure. (B) Overnight cultures of WT (RN6390B), Δagr (RN6911), ΔluxS and Δagr ΔluxS were inoculated in 24-well plate and formed biofilms under anaerobic conditions. (C) WT, Δagr, ΔluxS and Δagr ΔluxS formed 5 days biofilms in a flow cell on the upper surface of the coverslips, which were cut and examined by scanning electron microscopy. (D) The anaerobic jar was used for monitoring the biofilm formation of the WT, Δagr, ΔluxS and Δagr ΔluxS, OD560 was measured after crystal violet staining.
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Figure 6: Additive effect played by the LuxS/AI-2 QS system and the agr-mediated QS system. (A) The ΔagrΔluxSG and RN6911G grew biofilms in the flow cell, and the representative images were measured by CLSM at the 3rd and 5th day of biofilm formation. Strains are indicated in the figure. (B) Overnight cultures of WT (RN6390B), Δagr (RN6911), ΔluxS and Δagr ΔluxS were inoculated in 24-well plate and formed biofilms under anaerobic conditions. (C) WT, Δagr, ΔluxS and Δagr ΔluxS formed 5 days biofilms in a flow cell on the upper surface of the coverslips, which were cut and examined by scanning electron microscopy. (D) The anaerobic jar was used for monitoring the biofilm formation of the WT, Δagr, ΔluxS and Δagr ΔluxS, OD560 was measured after crystal violet staining.

Mentions: In the flow-cell assay, as shown in Figure 6A, the Δagr ΔluxS strain formed stronger biofilms than RN6911, as shown by CLSM, indicating that mutation of luxS indeed influences biofilm formation and that the two systems seem to play a cumulative effect. Moreover, similar results were obtained in the microtitre plate assay and the anaerobic jar assay under anaerobic conditions (Figure 6B and D).


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)

Additive effect played by the LuxS/AI-2 QS system and the agr-mediated QS system. (A) The ΔagrΔluxSG and RN6911G grew biofilms in the flow cell, and the representative images were measured by CLSM at the 3rd and 5th day of biofilm formation. Strains are indicated in the figure. (B) Overnight cultures of WT (RN6390B), Δagr (RN6911), ΔluxS and Δagr ΔluxS were inoculated in 24-well plate and formed biofilms under anaerobic conditions. (C) WT, Δagr, ΔluxS and Δagr ΔluxS formed 5 days biofilms in a flow cell on the upper surface of the coverslips, which were cut and examined by scanning electron microscopy. (D) The anaerobic jar was used for monitoring the biofilm formation of the WT, Δagr, ΔluxS and Δagr ΔluxS, OD560 was measured after crystal violet staining.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Additive effect played by the LuxS/AI-2 QS system and the agr-mediated QS system. (A) The ΔagrΔluxSG and RN6911G grew biofilms in the flow cell, and the representative images were measured by CLSM at the 3rd and 5th day of biofilm formation. Strains are indicated in the figure. (B) Overnight cultures of WT (RN6390B), Δagr (RN6911), ΔluxS and Δagr ΔluxS were inoculated in 24-well plate and formed biofilms under anaerobic conditions. (C) WT, Δagr, ΔluxS and Δagr ΔluxS formed 5 days biofilms in a flow cell on the upper surface of the coverslips, which were cut and examined by scanning electron microscopy. (D) The anaerobic jar was used for monitoring the biofilm formation of the WT, Δagr, ΔluxS and Δagr ΔluxS, OD560 was measured after crystal violet staining.
Mentions: In the flow-cell assay, as shown in Figure 6A, the Δagr ΔluxS strain formed stronger biofilms than RN6911, as shown by CLSM, indicating that mutation of luxS indeed influences biofilm formation and that the two systems seem to play a cumulative effect. Moreover, similar results were obtained in the microtitre plate assay and the anaerobic jar assay under anaerobic conditions (Figure 6B and D).

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