Abstract
Biofilms play a crucial role in the pathogenicity of Staphylococcus epidermidis, while little is known about whether the essential YycFG two-component signal transduction system (TCS) is involved in biofilm formation. We used antisense RNA (asRNA) to silence the yycFG TCS in order to study its regulatory functions in S. epidermidis. Strain 1457 expressing asRNAyycF exhibited a significant delay (~4–5 h) in entry to log phase, which was partially complemented by overexpressing ssaA. The expression of asRNAyycF and asRNAyycG resulted in a 68 and 50% decrease in biofilm formation at 6 h, respectively, while they had no significant inhibitory effect on 12 h biofilm formation. The expression of asRNAyycF led to a ~5-fold increase in polysaccharide intercellular adhesion (PIA) production, but it did not affect the expression of accumulation-associated protein (Aap) or the release of extracellular DNA. Consistently, quantitative real-time PCR showed that silencing yycF resulted in an increased transcription of biofilm-related genes, including icaA, arlR, sarA, sarX, and sbp. An in silico search of the YycF regulon for the conserved YycF recognition pattern and a modified motif in S. epidermidis, along with additional gel shift and DNase I footprinting assays, showed that arlR, sarA, sarX, and icaA are directly regulated by YycF. Our data suggests that YycFG modulates S. epidermidis biofilm formation in an ica-dependent manner.
Highlights
The coagulase-negative Staphylococcus epidermidis, an opportunistic pathogen, has become the most common source of infections associated with indwelling medical devices (Simon et al, 2005; Gordon et al, 2006)
We investigated the regulatory role of YycFG transduction system (TCS) in S. epidermidis biofilm formation by means of in vitro experiments and in silico techniques
We showed that YycFG TCS is a key regulator for S. epidermidis viability and negatively regulates S. epidermidis biofilm formation in an ica-dependent way
Summary
The coagulase-negative Staphylococcus epidermidis, an opportunistic pathogen, has become the most common source of infections associated with indwelling medical devices (Simon et al, 2005; Gordon et al, 2006). The pathogenicity of S. epidermidis is mainly attributed to biofilm formation, which involves multiple matrix components and regulators (Fey and Olson, 2010; Flemming et al, 2016). The matrix of the three-dimensional structured staphylococcal biofilm is mainly composed of extracellular polymeric substances (EPS), which includes polysaccharide intercellular adhesion (PIA) (O’Gara, 2007) and extracellular DNA (eDNA) (Qin et al, 2007). PIA, the major component of staphylococcal biofilm, is synthesized by proteins encoded by icaADBC, which are negatively regulated by the transcriptional repressor IcaR (Jefferson et al, 2003). In S. epidermidis, Aap is a major component of protein-dependent biofilm formation (Conrady et al, 2008), and a recent study revealed that a Small basic protein (Sbp) serves as an essential scaffold between the B domains of two Aap molecules during cell aggregation (Decker et al, 2015)
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