Identification of Genes Controlled by the Essential YycFG Two-Component System Reveals a Role for Biofilm Modulation in .

Biofilms play a crucial role in the pathogenicity of , 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 TCS in order to study its regulatory functions in . Strain 1457 expressing asRNA exhibited a significant delay (~4-5 h) in entry to log phase, which was partially complemented by overexpressing . The expression of asRNA and asRNA 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 asRNA 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 resulted in an increased transcription of biofilm-related genes, including , and . An search of the YycF regulon for the conserved YycF recognition pattern and a modified motif in , along with additional gel shift and DNase I footprinting assays, showed that , and are directly regulated by YycF. Our data suggests that YycFG modulates biofilm formation in an ica-dependent manner.