Differential effects of amino acid analogs on growth and heterocyst differentiation in two nitrogen-fixing blue-green algae

Abstract

Effects of a few amino acid analogs on growth and heterocyst differentiation have been studied in two nitrogen-fixing species of Anabaena. All the analogs except α-methyl-dl-aspartic acid inhibited growth. Exposure of Anabaena doliolum, to dl-5-fluorotryptophan and dl-p-fluorophenylalanine caused pronounced fragmentation of filaments into single cells. At low concentrations (0.01 mM), α-methyl-dl-aspartic acid stimulated growth of the strain of A. doliolum as well as the strain of the second (unidentified)Anabaena species. Ethionine, dl-p-fluorophenylalanine, dl-5-fluorotryptophan, and canavanine blocked heterocyst differentiation, whereas α-methyl-dl-aspartic acid, α-methyl-dl-methionine, N-o-nitrophenylsulfenyl-l-tryptophan, norleucine, and S-2-aminoethyl-l-cysteine did not show any significant effect. Treatment with 7-azatryptophan, dl-β-hydroxynorvaline, l-methionine-dl-sulfoximine, l-methionine sulfone, and β-2-thienyl-dl-alanine led to a twofold increase in heterocyst frequency. Possible modes of action of the analogs in growth inhibition and changes in heterocyst frequency are discussed. © 1980 Springer-Verlag New York Inc.