HIGH-IONIC STRENGTH INTERFERENCE OF RIBOSOMAL INHIBITION PRODUCED BY AMINOGLYCOSIDE ANTIBIOTICS

A protein synthesis cell-free system capable of performing with simila r efficiencies in different ionic conditions has been developed for th e halotolerant marine bacterium Vibrio costicola. The system has been used to test the effect of ionic strength on the interference produced by thirty translation inhibitors with different structural, functiona l, and domain specificities. In general, at high ionic strengths, the inhibition of protein synthesis produced by polycationic antibiotics l ike the aminoglycosides is much less pronounced than the inhibition ob tained at low ionic strengths, while non-aminoglycosidic antibiotics s how similar inhibitory activities at both high and low ionic condition s. These results strongly suggest that competition between polycationi c antibiotics and cations at high concentrations in the media is respo nsible for the lack of inhibition by aminoglycoside antibiotics at hig h ionic strengths, rather than a lack of binding sites.