AMINOGLYCOSIDE AND AMINOCYCLITOL ANTIBIOTICS - HYGROMYCIN-B IS AN ATYPICAL BACTERICIDAL COMPOUND THAT EXERTS EFFECTS ON CELLS OF ESCHERICHIA-COLI CHARACTERISTIC FOR BACTERIOSTATIC AMINOCYCLITOLS

The effects of aminoglycoside and aminocyclitol antibiotics on intact cells of Escherichia coli were compared. The aminoglycosides streptomycin, gentamicin, kanamycin and neomycin had similar, but not identical, effects. They all caused misreading during protein synthesis, permeabilization of the cell membrane, inhibition of the initiation of DNA replication, and loss of cell viability. Cells treated with these antibiotics continued to synthesize two proteins (apparent molecular masses 72 and 60 kDa) that were not made by cells treated with the aminocyclitol hygromycin B, which did not cause misreading. Cells treated with the aminoglycosides regained their membrane tightness after residual protein synthesis in these cells had been inhibited by chloramphenicol, suggesting that under these conditions the mistranslated membrane proteins were rapidly degraded. The bacteriostatic aminocyclitols spectinomycin and kasugamycin did not cause membrane permeabilization, suggesting that these compounds do not cause misreading. Hygromycin B resembled these aminocyclitols in that it inhibited protein synthesis without causing misreading, membrane permeabilization or inhibition of initiation of DNA synthesis. However, hygromycin B also decreased cell viability. In minimal medium this lethal effect began late in comparison to the process of inhibition of protein synthesis. It is concluded that hygromycin B is an atypical bactericidal antibiotic that strongly resembles the bacteriostatic aminocyclitols spectinomycin and kasugamycin in its action.