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

Abstract

BackgroundStaphylococcus 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.ResultsHere 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.ConclusionThese 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.

Pfs promotes autolysis-dependent release of eDNA and biofilm formation in Staphylococcus aureus

“…3b). These results suggest that the defect of the pfs mutant strain in biofilm formation is not because of the disruption of AI-2, consistent with our previous studies showing that the S. aureus AI-2 reduces biofilm formation [22].…”

“…The addition of in vitro-synthesized AI-2 did not restore the biofilm formation of the pfs mutant strain under either static or dynamic flow conditions, which suggest that the defect of the pfs mutant strain in biofilm formation is not because of the disruption of AI-2. In a previous study, we also showed that S. aureus AI-2 quorum-sensing reduces biofilm formation [22]. This means that pfs and AI-2 have opposite effect on biofilm formation.…”

“…It has been reported that Pfs inhibitors disrupt AI-2 production in Vibrio cholerae and Escherichia coli in a dose-dependent manner without affecting growth and biofilm formation in these organisms [21]. We have previously shown that AI-2 reduces S. aureus biofilm formation via the icaR activation pathway [22], and Pfs is essential for AI-2 production [23]. The aim of the present study is to investigate the role of Pfs in S. aureus biofilm formation.…”

Measurement of Predation and Biofilm Formation under Different Ambient Oxygen Conditions Using a Simple Gasbag-Based System

“…Although biofilm formation under low-oxygen conditions was measured for many of the bacteria examined in this study (45)(46)(47)(48)(49), the new gasbag system allows measuring biofilm growth and physiology under gas conditions that are not easily attained using, for the most part, standard lab equipment. The gasbag system might also facilitate studies that are aimed at understanding the effect of oxygen therapy on microbial physiology and pathogenesis (50)(51)(52).…”

Biofilm: An Important Bacterial Feature Still to Deal With

“…Some of these enzymes are under the control of QS [71,72]. The cell dispersion process takes place through the QS that allows the formation of small agglomerates and a new biofilm formation [73].…”