A potentially new thermotolerant B. licheniformis strain (code name I89), producer of an antibiotic active against Gram-positive bacteria, was genetically characterized and compared with the type strain B. licheniformis ATCC 10716, producer of bacitracin, Studies on DNA base composition (G + C content) and DNA reassociation revealed that the two strains show around 76% homology. Nevertheless, results obtained by rRNA hybridization, with a heterologous probe coding for most of the 16S region of the rRNA operon of Bacillus subtilis, revealed differences in the number of copies for that gene and in the hybridization pattern. Additionally, a different restriction digestion pattern was obtained when DNA was digested with the enzymes NotI, SmaI and analyzed by PFGE. The I89 strain holds a 7.6-kb plasmid not present in the reference strain. The existence of various unique restriction sites and also the stability of this plasmid make it ideal for the future development of a cloning and expression vector.