Spermidine in the Bacterial Cell

SUMMARY The concentration of spermidine in extracts of various micro-organisms was determined; Neurospora crassa contained the highest concentrations of spermidine, while in Pseudomonas aeruginosa, Escherichia coli and Saccharomyces cerevisiae the concentration of spermidine was lower. Growing organisms and cell-free extracts of the micro-organisms tested were able to synthesize [14C]spermidine from dl-[2-14C]methionine. Cell-free extracts of Pseudomonas aeruginosa were most active in this respect. [14C]Spermidine formed by growing Bacillus subtilis was localized in both the protoplasts and the bacterial cell walls. The kinetics of the adsorption of [14C]spermidine on to cell walls and protoplasts of B. subtilis were also studied. The interpretation of these observations and their relation to the antibacterial effect and growth-promoting activity of spermidine are discussed.