Enzymes, synthesized in bacterial SOS response, enable bacterial organisms to repair DNA damage and therefore easily adapt to stresful enviroments and chemical agenses. Acinetobacter baumannii strains are resistant to a large range and variety of antibiotics. During SOS response Acinetobacter baumannii synthesize small protein molecule, named DdrR, which is specific only for genus Acinetobacter and can be found no where else. When synthesized, DdrR co-regulates transcription of SOS damage inducible genes together with main bacterial protein regulator, UmuDAb. In the study we examined if DdrR binds directly to UmuDAb protein and to two other phage repressors, which regulate lizogenic cycle of two temperate prophages, situated in bacterial chromosomal DNA. Surface plasmon resonance analysis indicated that DdrR protein binded succesfully to all analyzed protein repressors, with high affinity, and, in this way, it most likely co-regulates transcription of bacterial and bacteriophage genes.