POLYAMINES OF FRANKIA IN RELATION TO NITROGEN NUTRITION

The occurrence of putrescine, cadaverine, spermidine and spermine as the main components of the free polyamine fraction of several strains of cultured Frankia is demonstrated. Putrescine was the major polyamine in virtually all strains irrespective of the source of nitrogen for growth (N2-fixation; NH4Cl; KNO3; hydrolysed casein (casamino acids). However, in cultures reliant solely on N2-fixation for growth amounts of cadaverine, spermidine and spermine more than doubled relative to putrescine. When polyamines were supplied as the sole source of organic nitrogen (8 mg N l-1), best growth of two strains of Frankia was supported by putrescine, with cadaverine also giving good growth in strain UGL140102. Growth with spermidine and spermine was less than with other sources of nitrogen, such as hydrolysed casein or N2-fixation. Cultures grown in spermine showed degeneration of the mycelium and a substantial reduction in numbers of vesicles formed on the mycelium compared with cultures grown with hydrolysed casein or with fixed N2. It is unlikely, therefore, that the polyamines tested play a specific role in vesicle initiation.