By culturing Lysobacter sp. BMK333-48F3 (deposit number of FERM BP-7477), an antibiotic, tripropeptin Z, tripropeptin A, tripropeptin B, tripropeptin C or tripropeptin D represented by the general formula (I): ##STR00001## wherein R is 7-methyl-octyl group, 8-methyl-nonyl group, 9-methyl-dodecyl group, 10-methyl-undecyl group or 11-methyl-dodecyl group, is obtained as antibiotics having excellent antibacterial activities against bacteria and having a novel molecular structure. These tripropeptins each have an excellent antibacterial activity against various bacteria and drug-resistant strains thereof, such as methicillin-resistant strains and vancomycin-resistant strains.