STREPTOMYCIN BACTERICIDAL ACTION IS DEPENDENT ON POLYAMINE ENDOGENOUSLEVELS IN ESCHERICHIA-COLI

E, coli polyamine-supplemented and depleted cultures showed an importa nt difference in survival to streptomycin; the bactericidal effect of the antibiotic was remarkably higher in cells with normal levels of po lyamines. Similar results were observed with kanamycin. Analysis of th e polyamine-containing cells pulse-labelled with S-35-methionine durin g streptomycin action indicated that the amounts of newly-synthesized peptides in various subcellular fractions was different from the amoun ts formed in the untreated controls; the most dramatic change was foun d in the residual particulate fraction where the antibiotic treatment caused a 3-fold increase of radioactive proteins. On the contrary, equ ivalent amounts of labelled peptides were detected in the different fr actions prepared from polyamine-depleted bacteria incubated with or wi thout antibiotic. In this case the corresponding residual fraction was only slightly increased. Sodium dodecyl sulfate-polyacrylamide gel el ectrophoresis of the different fractions showed some changes elicited by streptomycin in the protein patterns of polyamine-containing bacter ia, especially in the residual fractions. The electrophoretic profile corresponding to deprived cells was very similar in all cases. The rol e of polyamines in the conformation of the outer membrane and in the c orrect assembly of ribosomes is discussed on account of the enhancing effect of these polycations on the bactericidal action of streptomycin .