The MarR protein of E. coli is a multidrug binding transcription regulator. A wide range of compounds, including 2,4-dinitrophenol, plumbagin, menadione, and salicylate, attenuate and inhibit its association with cognate DNA [26] . In our previous study, salicylate and multiple antibiotics interfered with the transcriptional repressor activity of TcaR [17] . These findings prompted the current investigation into the possible effects of antibiotics on the ssDNA binding ability of TcaR. Here, to investigate the possible effect of some drugs on TcaR, four compounds were tested for their potential inhibition on TcaR-ssDNA interaction. These include one beta-lactam antibiotics (ampicillin) that contain a b-lactam nucleus in their molecular structure and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls, two aminoglycoside antibiotics (kanamycin and gentamicin) that composed of several sugar groups and amino groups, and bacteriostatic antimicrobial (chloramphenicol) which is considered as a prototypical broad-spectrum antibiotic.