Streptomycin bactericidal action is dependent on polyamine endogenous levels in E. coli.

E. coli polyamine-supplemented and depleted cultures showed an important difference in survival to streptomycin; the bactericidal effect of the antibiotic was remarkably higher in cells with normal levels of polyamines. Similar results were observed with kanamycin.

In vitro studies on ppGpp synthetase I from polyamine-starved and unstarved Escherichia coli.

We have studied the in vitro formation of guanosine 5'-diphosphate 3'-diphosphate (ppGpp) using a partially purified ppGpp synthetase I (PSI) from Escherichia coli BGA8, a polyamine auxotrophic strain. A comparison of the enzyme obtained from polyamine-supplemented or deprived bacteria showed similar requirements for the reaction, Mg+2 optimum levels and sparing effect of spermidine. No differences in the inhibitory effects of tetracycline, puromycin and fusidic acid were detected either.

A role for polyamines in the control of ppGpp levels in Escherichia coli.

As an approach to understand the involvement of polyamines in the variation of intracellular guanosine 5'-diphosphate 3'-diphosphate (ppGpp) levels, kinetic studies with several polyamine-requiring relA and spoT Escherichia coli mutants have been carried out. The accumulation and turnover of the nucleotide have been followed under conditions of aminoacid depletion or energy source starvation. The results obtained strongly suggest an important role of the polycations mainly in the degradation of ppGpp, and also in its synthesis mediated by ppGpp synthetase I (PSI).

Polyamines and cell wall organization in Saccharomyces cerevisiae.

Cells of Saccharomyces cerevisiae 179-5, an ornithine decarboxylase mutant (spe-1), showed several ultrastructural abnormalities when cultivated in the absence of polyamines. Besides the appearance of microvacuole-like spaces in the cytoplasm and of deformed nuclei, the most important alterations seemed to be located in the cell wall, which was thicker and of heterogeneous texture, and in the cell membrane, of irregular contour. These modifications could not be evoked by general stress conditions elicited by lack of nutrients.