Abstract:Three algae-lysing bacteria (L7、L8、L18) have been isolated. We used starch medium, which has no passive effect on growth of the Anabaena flos-aquae as cutivate medium. After being cultivated for 4d on a reciprocal shaker at 30℃ and a speed of 100 r/min, the cultivate broth were centrifugated at a speed of 4000 r/min for 20min、filtrated with 0.22 mm membrane, and condensed by vacuum rotary evaporator at 65℃. The sterile condensed bacteria-free filtrate obtained are dialysed, sedimentated by ethanol, extracted by organic solvents, absorbed by activated carbon. The molecular weight of the extracellular algae-lysing components of L7 are less than 3.5 kD, while the molecular weight of extracellular algae-lysing components of L8 and L18 are between 3.5 kD~7 kD; ethanol can not separate extracellular algae-lysing components from other componets efficiently; carbon tetrachloride can separate the extracellular algae-lysing components of L7 into water-layer efficiently, while petroleum ether can separate the extracellular algae-lysing components of L8 and L18 into water-layer efficiently, the extracellular algae-lysing