Factors Affecting Formation of Spores (Akinetes) in Cyanobacterium Anabaena doliolum (AdS strain)

Abstract

The effect of various physical and chemical factors on spore formation of Anabaena doliolum [AdS strain*)] was investigated under laboratory conditions. Among the three inorganic nitrogen sources, nitrate and nitrite (0.5 mM) were slightly stimulatory to sporulation, however, the specific growth rate was reduced in comparison to N-free grown culture. Ammonium (all concentrations) was inhibitory to growth as well as to sporulation. Dilution of phosphate in the medium was stimulatory whereas dilution of the medium was inhibitory to sporulation. Temporal relationship between spore differentiation, depletion of phosphate from the medium, and development of alkaline phosphatase activity suggest that induction of this enzyme may be considered as one of the important events preceeding sporulation. Metabolic inhibitors like sodium azide, sodium fluoride, and sodium arsenate were stimulatory either in terms of the time required for sporulation or the spore frequency. Growth rate as well as sporulation of A. doliolum was more enhanced at 32 ±2 °C than at 25 ±1 °C. Increasing light intensities (from 500lx to 3,000lx) increased the sporulation frequency with a gradual decrease in the time required for spore initiation. pH 8.0 of the medium was most suitable for sporulation. © 1987, Gustav Fischer Verlag, Stuttgart. All rights reserved.