Effects of Kanamycin and Streptomycin on the Macromolecular Composition of Streptomycin-Sensitive and Resistant Escherichia coli Strains

Abstract

Kanamycin and streptomycin are both aminoglycoside antibiotics that bind to the 30S ribosomal subunit and inhibit protein translation. Kanamycin may have potential secondary targets in Escherichia coli other than the protein synthesis machinery. The aim of this study was to find evidence against the existence of secondary targets by subjecting kanamycin-resistant and kanamycin-sensitive E. coli strains to the antibiotic and examining the resulting impact on the macromolecular composition of the cells. The concentrations of antibiotic used were too low to inhibit growth and an unexpected increase in the protein/carbohydrate content of sensitive cells was observed. We believe this increase is due to an accumulation of a large number of non-functional polypeptides in addition to the normal protein constituent required for growth. It is likely that numerous non-functional proteins did result from growth in the presence of a non-inhibitory concentration of these aminoglycosides. Only the protein/carbohydrate fraction of the E. coli was dramatically altered by the presence of an aminoglycoside. Although no evidence of kanamycin secondary effects were detected, due to experimental difficulties we are unable to say that they are non-existent.