ANATOXIN-A CONCENTRATION IN ANABAENA AND APHANIZOMENON UNDER DIFFERENT ENVIRONMENTAL-CONDITIONS AND COMPARISON OF GROWTH BY TOXIC AND NONTOXIC ANABAENA-STRAINS - A LABORATORY STUDY

Anatoxin-a-concentration in cells of Anabaena- and Aphanizomenon-strai ns and in their growth media. were studied in the laboratory in batch cultures at different temperatures, light fluxes, orthophosphate and n itrate concentrations and with different nitrogen sources for growth. Toxin concentrations were detected by HPLC. Also, the growth of the to xic Anabaena-strains was compared to that of a non-toxic one. The non- toxic Anabaena was never found to produce anatoxin-a. The amount of to xin in the cells of the toxic strains was high, often exceeding 1% of their dry weight. High temperature decreased the amount of the toxin r egardless of growth. Growth limiting low and growth inhibiting high li ght decreased the amount of the toxin in the cells of Anabaena-strains . The highest light flux studied did not limit the growth or decrease the level of the toxin in the cells of Aphanizomenon. Growth in N-free medium (i.e. N-2 fixation) showed that the cells contained more toxin than growth in N-rich medium. Orthophosphate concentration had no eff ect on toxin levels, although the lowest concentrations limited the gr owth of ah strains studied. The toxic strains tolerated higher tempera tures than the non-toxic one, but the non-toxic strain seemed to be mo re adjustable to high irradiance than the toxic ones. The yields (dry weight) of non-toxic and toxic strains differed significantly in diffe rent phosphate concentrations.