has_part gramicidin gramicidin D antibiotic_resistance PubChem:45267103 Gramicidin D is a mixture of the linear peptides gramicidin A, B, and C, each with 15 alternating L- and D-amino acids. They are active against most gram-positive bacteria and select gram-negative bacteria. These compounds create channels in the bacterial membrane and increase the permeability to cations. ARO:3000199 gramicidin A gramicidin B gramicidin C antibiotic mixture