An effective activity-guided purification strategy was applied to purify halocin HA1 from cell-free supernatant (CFS) of Haloferax larsenii HA1. The yield of the purified halocin was 12.8%, with specific antimicrobial activity of 12.16 AU mu g(-1) Halocin activity was stable up to 121 degrees C and pH 4.0-12.0 Nit reduced in the presence of proteinase K and trypsin, suggesting the proteinaceous nature of the compound. It was halocidal against H. larsenii HA10 and caused cellular deformation and release of cell contents leading to cell death. The halocidal activity was also found against the other strains of haloarchaea tested. The molecular mass of halocin HA1 was similar to 14 kDa, as determined by tricine SDS-PAGE. MALDI-TOF MS/MS and N-terminal sequencing indicated no apparent homology with known halocins, suggesting that this is a new compound. These properties of halocin HA1 may be useful for the preservation of salted foods and leather hides in food and leather industries.