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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

Transcriptional regulation of icaA and icaR by AI-2. Real-time RT-PCR of icaA and icaR transcription was measured. The bacteria used for RNA extraction were those that were incubated at 4 h for biofilm formation under aerobic conditions. Error bars indicate the variation between triplicate samples within the real-time RT-PCR. The relative cDNA abundance of the WT sample was assigned a value of 1. (A) Relative transcript levels of icaA of WT (RN6390B), ΔluxS and ΔluxS complemented with 3.9 nM DPD under aerobic conditions. (B) Relative transcript levels of icaR of WT (RN6390B), ΔluxS and ΔluxS complemented with 3.9 nM DPD under aerobic conditions.
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Figure 4: Transcriptional regulation of icaA and icaR by AI-2. Real-time RT-PCR of icaA and icaR transcription was measured. The bacteria used for RNA extraction were those that were incubated at 4 h for biofilm formation under aerobic conditions. Error bars indicate the variation between triplicate samples within the real-time RT-PCR. The relative cDNA abundance of the WT sample was assigned a value of 1. (A) Relative transcript levels of icaA of WT (RN6390B), ΔluxS and ΔluxS complemented with 3.9 nM DPD under aerobic conditions. (B) Relative transcript levels of icaR of WT (RN6390B), ΔluxS and ΔluxS complemented with 3.9 nM DPD under aerobic conditions.

Mentions: PIA is considered to be a major factor determining biofilm formation in some bacteria [10,54,55]. To test if AI-2-mediated biofilm reduction is due to a change in PIA expression, the transcription of icaA was examined using real-time RT-PCR with RNA isolated from biofilm bacteria at different time points. Transcription of icaA reached its peak at 4 h of biofilm formation and the maximum difference between the WT strain and the ΔluxS strain was also highlighted at this time (data not shown). Thus, RNA was isolated from 4 h biofilm bacteria of the WT strain, the ΔluxS strain, and the ΔluxS strain complemented with 3.9 nM DPD. Expression of icaA was examined using real-time RT-PCR. The resulting data showed that expression of icaA was elevated in the ΔluxS strain, and it could be complemented by 3.9 nM DPD (Figure 4A). As expected, corresponding to the biofilm formation in Figure 1, thicker biofilms were presented owing to the luxS mutation while the bacteria within the biofilms also displayed elevated icaA transcription. Moreover, we examined the expression of several main adhesion molecules. As shown in Additional file 1: Figure S1, there were no obvious differences between the WT, ΔluxS and ΔluxS transformed with the pLIluxS plasmid for complementation (ΔluxSpluxS). Here, the WT and ΔluxS strains were also transformed with an empty PLI50 plasmid constructing the WTp strain and ΔluxSp strain, which were used as the control. Besides, we added sodium-metapeiodate into the well-developed biofilms and found that biofilms dispersed after 2 h incubation at 37°C. Taken together, our results suggest that PIA is the main factor controlled by AI-2 in the regulation of biofilm formation in S. aureus.


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)

Transcriptional regulation of icaA and icaR by AI-2. Real-time RT-PCR of icaA and icaR transcription was measured. The bacteria used for RNA extraction were those that were incubated at 4 h for biofilm formation under aerobic conditions. Error bars indicate the variation between triplicate samples within the real-time RT-PCR. The relative cDNA abundance of the WT sample was assigned a value of 1. (A) Relative transcript levels of icaA of WT (RN6390B), ΔluxS and ΔluxS complemented with 3.9 nM DPD under aerobic conditions. (B) Relative transcript levels of icaR of WT (RN6390B), ΔluxS and ΔluxS complemented with 3.9 nM DPD under aerobic conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Transcriptional regulation of icaA and icaR by AI-2. Real-time RT-PCR of icaA and icaR transcription was measured. The bacteria used for RNA extraction were those that were incubated at 4 h for biofilm formation under aerobic conditions. Error bars indicate the variation between triplicate samples within the real-time RT-PCR. The relative cDNA abundance of the WT sample was assigned a value of 1. (A) Relative transcript levels of icaA of WT (RN6390B), ΔluxS and ΔluxS complemented with 3.9 nM DPD under aerobic conditions. (B) Relative transcript levels of icaR of WT (RN6390B), ΔluxS and ΔluxS complemented with 3.9 nM DPD under aerobic conditions.
Mentions: PIA is considered to be a major factor determining biofilm formation in some bacteria [10,54,55]. To test if AI-2-mediated biofilm reduction is due to a change in PIA expression, the transcription of icaA was examined using real-time RT-PCR with RNA isolated from biofilm bacteria at different time points. Transcription of icaA reached its peak at 4 h of biofilm formation and the maximum difference between the WT strain and the ΔluxS strain was also highlighted at this time (data not shown). Thus, RNA was isolated from 4 h biofilm bacteria of the WT strain, the ΔluxS strain, and the ΔluxS strain complemented with 3.9 nM DPD. Expression of icaA was examined using real-time RT-PCR. The resulting data showed that expression of icaA was elevated in the ΔluxS strain, and it could be complemented by 3.9 nM DPD (Figure 4A). As expected, corresponding to the biofilm formation in Figure 1, thicker biofilms were presented owing to the luxS mutation while the bacteria within the biofilms also displayed elevated icaA transcription. Moreover, we examined the expression of several main adhesion molecules. As shown in Additional file 1: Figure S1, there were no obvious differences between the WT, ΔluxS and ΔluxS transformed with the pLIluxS plasmid for complementation (ΔluxSpluxS). Here, the WT and ΔluxS strains were also transformed with an empty PLI50 plasmid constructing the WTp strain and ΔluxSp strain, which were used as the control. Besides, we added sodium-metapeiodate into the well-developed biofilms and found that biofilms dispersed after 2 h incubation at 37°C. Taken together, our results suggest that PIA is the main factor controlled by AI-2 in the regulation of biofilm formation in S. aureus.

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