Streptolydigin. Molecular model of the antibiotic drug streptolydigin (C32.H44.N2.O9). This drug acts by blocking nucleic acid chain elongation by binding to the polymerase enzyme. It is used to treat infections by Gram-positive bacteria. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue) and oxygen (red).