Erythromycin antibiotic is synthesised by Streptomyces erythraeus. It is usually bacteriostatic and binds with the $23 \,S \, rRNA $ of the $50\,S$ ribosomal subunit to inhibit peptide chain elongation during protein synthesis. Erythromycin is a relatively broad-spectrum antibiotic it is effective against Gram-positive bacteria mycoplasmas and a few Gram-negative bacteria.