Represses transcription of the icaADBC operon necessary for biofilm production. Homodimer. Repressed by ethanol. Cells lacking this gene display a 5.8-fold increase in ica operon expression. Binding to the ica operator DNA involves two IcaR dimers and is highly cooperative. Two aminoglycoside antibiotics, namely, gentamicin and streptomycin, show an inhibitory effect on the IcaR-DNA interactions. Consequently, by interfering with the binding of IcaR to DNA, aminoglycoside gentamicin and other antibiotics may activate the icaADBC genes and elicit biofilm production in S.epidermidis, as a defense mechanism. The four antibiotics kanamycin, tetracycline, ampicillin and chloramphenicol do not show significant effect on the IcaR-DNA binding.