The bacterial chromosome is organized into loops, which constitute topologically isolated domains. It is unclear which proteins are responsible for the formation of the topological barriers between domains. The abundant DNA-binding histone-like nucleoid structuring protein (H-NS) is a key player in the organization and compaction of bacterial chromosomes [1,2]. The protein acts by bridging DNA duplexes , thus allowing for the formation of DNA loops. Here, genome-wide studies of H-NS binding suggest that this protein is directly involved in the formation or maintenance of topological domain barriers.