SUMMARY: Two screening methods for isolation of mutants of with altered control of nitrogen metabolism enzymes are described. Thirty-eight profotrophic mutants with simultaneous deregulation of urease and glutamine synthetase were isolated. Nine mutants were examined in more detail and they also showed deregulated formation of arginase and ornithine aminotransferase. Different patterns of altered control of all four enzymes were observed Inactivation of glutamine synthetase after ammonium shock took place to different extents in these nine strains, and seven of them had a thermosensitive glutamine synthetase activity. It is concluded that a system of nitrogen control, in which glutamine synthetase has a key role, is present in Cephalosporin production was depressed by ammonium in all the mutants, irrespective of the alterations in nitrogen control of primary metabolism.


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