An orange cheese coryneform bacterium isolated from the surface of Gruyère of Comté and identified as Brevibacterium linens produces an antimicrobial substance designated linenscin OC2. This compound inhibits gram-positive food-borne pathogens including Staphylococcus aureus and Listeria monocytogenes but is not active against gram-negative bacteria. Linenscin OC2 caused viability loss and lysis of the test organism, Listeria innocua. Electron microscopy showed that linenscin OC2 induces protoplast formation and cell lysis. The native substance is resistant to proteolytic enzymes, heat, and organic solvents and stable over a wide range of pH. The molecular weight of the native linenscin OC2 was estimated by gel chromatography to be over 285,000. Linenscin OC2 was purified by ammonium sulfate precipitation, 2-propanol extraction, and reverse-phase chromatography. Direct detection of antimicrobial activity on a sodium dodecyl sulfate-polyacrylamide gel suggested an apparent molecular mass under 2,412 Da. Molecular mass was determined to be 1,196.7 Da by mass spectrometry. Amino acid composition analysis indicated that linenscin OC2 may contain 12 residues.