The bacterial ribosomal structure and the accessory functions differ in many respects from its eukaryotic equivalent. The translation reaction itself can be subdivided into three parts: 1.Formation of the initiation complex, blocked by Streptomycin and Tetracyclins (the latter inhibiting binding of aa-tRNA to the ribosomal A- site at the 30S ribosomal subunit. 2.Introduction of aa-tRNA and synthesis of a peptide bond, inhibited by puromycin (leading to premature termination) and chloramphenicol (probably inhibiting the peptidyltransferase). 3.Translocation of the mRNA relative to the ribosome blocked by erythromycin and fusidic acid (the latter preventing release of EF-G/GDP.