APPARENT PREDATION OF MICROCYSTIS AERUGINOSA KüTZ. EMEND ELENKIN BY A SAPROSPIRA -LIKE BACTERIUM IN A HYPERTROPHIC LAKE (HARTBEESPOORT DAM, SOUTH AFRICA)

SUMMARY The cyanobacterium Microcystis aeruginosa is the dominant autotroph in hypertrophic Hartbeespoort Dam, South Africa. Tn early summer (November) of 1983 and 1984 Microcystis colonies were heavily colonized by a gram-negative, spiral-shaped organism whose filaments appeared as si.ngle cells under both the light and scanning electron microscope. DNA staining with 4'6 diamidino-2-phenylindole (DAPI) revealed that each filament consisted of a number of bow-shaped cells. The organism has been tentatively identified as a bacterium, Saprospira albida, on the basis of it morphology. The Microcystis cells at the site of colonization were apochlorotic suggesting lysis by Saprospira.