The bactericidal toxin CcdB is encoded by the F plasmid ccd (control of cell division) locus, as part of a two-component system of the programmed cell death in Escherichia coli. CcdB acts as a toxin and CcdA as the antidote. In the absence of CcdA, CcdB can kill bacteria by a mechanism that involves DNA gyrase. DNA gyrase is a bacterial type II topoisomerase involved in DNA replication and transcription. The enzyme consists of two subunits, A (GyrA) and B (GyrB), whose active form is A₂B₂. CcdB blocks the gyrase activity by stabilization of a "cleavable complex" through a mechanism still unclear which the Arg462 residue of GyrA and the C-terminal fragment of CcdB toxin (Trp99 – Ile101) seem to be involved. As an approach to this mechanism as well as the development of a new family of inhibitors of DNA gyrase, we have synthesized a series of peptide fragments containing specific sequences of the natural CcdB protein. Previous results of supercoiling assays selected CcdB2 peptide as a potential inhibitor of Gyrase activity (MIC = 96 µg mL^-1). CcdB2 encapsulated in Liposome (SUV) was able to inhibit the bacterial growth in liquid culture medium. The growth inhibition in vitro was about 50% for Pseudomonas sp, Streptococcus agalactae, Salmonella sp. and Klebsiella pneumoniae, and about 30% for Escherichia coli K-12, Sthaphilococcus aureus and Shigella sp.