Involved in the antibiotic teicoplanin susceptibility. Inactivation of the tcaRAB operon leads to teicoplanin resistance. Is a weak negative regulator of transcription of the icaADBC operon necessary for biofilm production. Cells display a 5-fold increase of the ica transcription but has no significant effect on the adherence ability nor on the amount of poly-N-acetylglucosamine polysaccharide (PNAG) produced with respect to the wild-type strain. Double deletion of icaR and tcaR increases ica transcription about 500-fold, and poly-N-acetylglucosamine polysaccharide (PNAG) synthesis about 100-fold. Adherence is significantly greater than that of the single icaR mutant.