PROLINE IS BIOSYNTHESIZED FROM ARGININE IN STAPHYLOCOCCUS-AUREUS

Staphylococcus aureus NCTC 8325 exhibited a long lag phase (11 h) when inoculated into defined medium lacking proline, that could be shorten ed by increasing the concentration of arginine in the medium, or by su pplying ornithine. Radioactivity from L-[C-14]arginine, but not L-[C-1 4]glutamate was incorporated into a spot with the chromatographic mobi lity of [C-14]proline in the pool metabolites fraction, Selection for transposon Tn917-lacZ mutants impaired in arginine catabolism yielded four proline auxotrophs. Enzyme assays and precursor feeding experimen ts suggested that the major pathway for proline biosynthesis in S. aur eus was from arginine via ornithine and Delta'-pyrroline 5-carboxylate , rather than from glutamate. Strain 8325 Pro(+), a proline prototroph ic variant obtained by cultivation of 8325 in the absence of proline, accumulated L-[C-14]arginine from the medium at about eight times the rate of strain 8325, suggesting its response to proline starvation was to increase arginine uptake.