As shown in Figure 1I , kanamycin, chloramphenicol and gentamycin interfered with the ssDNA (GC33) binding activity of TcaR at a concentration of 2 mM and this effect was more pronounced at a higher concentration, suggesting that antibiotics inhibit formation of the TcaR-ssDNA complex. Results indicated that ampicillin also antagonized the ssDNA binding activity of TcaR at a concentration of 20 mM. This result is consistent with the observation seen in SPR, as discussed below. Taken together, we believe that diverse kinds of antibiotics may interact with TcaR to regulate its ssDNA binding ability.