Abstract
Several .beta.-lactams were investigated on the affinity for the penicillin-binding proteins (PBP) and the antibacterial activity in B. subtilis. The .beta.-lactams such as ampicillin, PS-5, methicillin and SCE-963, which had high affinities for PBP-2 showed strong antibacterial activities and the .beta.-lactams such as cephamycin C, Y-G19Z-GG and Y-G19Z-G, which had high affinities for PBP-1 but low affinities for PBP-2, showed weak antibacterial activities. Clavulanic acid and nocardicin A, which had almost no affinities for all the PBP detected, showed very low antibacterial activities. These results suggest that PBP-2 in B. subtilis is the lethal target of these .beta.-lactam antibiotics.