[Reactions of cyanobacteria to certain heavy metals]

The effect of zinc and cobalt chlorides on cellular growth, N2 fixation, photosynthesis and changes in the content of Na+ and K+ ions in cells was studied with the blue-green alga (cyanobacterium) Anabaena spheroides. The cells were most susceptible to the action of cobalt ions at the beginning of the logarithmic growth phase, and least sensitive by the end of the phase. Cobalt ions were more toxic than zinc ions. The salts of heavy metals inhibited active transport of ions into the algal cells.