DE-REGULATED ASSIMILATION AND OVER-PRODUCTION OF AMINO-ACIDS IN ANALOG-RESISTANT MUTANTS OF A CYANOBACTERIUM, PHORMIDIUM-UNCINATUM

Mutant strains of Phormidium uncinatum resistant to fluoro-phenylalani ne, azatryptophan, fluorotyrosine and azaleucine accumulated a wide ra nge of amino acids, notably glutamic acid, lysine, tyrosine and phenyl alanine, and exhibited de-regulated valine and phenylalanine transport . While acetohydroxy acid synthase in azaleucine-resistant mutants los t valine- and leucine-sensitivity, 3-deoxy-D-arabinoheplulosonate-7-ph osphate (DAHP) synthase and prephenate dehydratase in aromatic analogu e-resistant strains became phenylalanine-insensitive and shikimate and prephenate dehydrogenases were activated by tyrosine. In addition, ac tivities of nitrate-assimilating enzymes were higher in the mutants, w hich also exhibited increased nitrogen, protein and phycocyanin conten ts, The proteins in the mutants were better digested upon enzymatic-tr eatments and feeding trials than those of the wild type, indicating th at they are usable as single-cell protein.