Brevibacillus brevis is a Gram-positive, aerobic, spore-forming bacillus commonly found in soil, air, water, and decaying matter. It is rarely associated with infectious diseases. The antibiotics gramicidin and tyrocidine were first isolated from it. Brevibacillus brevis forms Gram-positive (variable) rods with optimal growth of 35-55°C. It is a motile spore-former with positive catalase activity, amylase negative, casein negative, gelatinase positive, and indole negative, and most are citrate users. Some strains are capable of oxidizing carbon monoxide aerobically.