Abstract: An strain of actinomycete JXJ 0071 was isolated from soil of the Lushan Mountain. Activities of its spores, mycelia and metabolites lysing Microcystis aeruginosa, stability of the active components of the activities and its taxonomic status were studied. Both spores and mycelia of actinomycete JXJ 0071 reduced the density of M. aeruginosa remarkably. Metabolites of the strain showed a very strong activity lysing M. aeruginosa, and 98% alga cells perished three days after addition of fermentation supernatant 2% in volume into the culture (1.0×10⁷ mL^-1) of M. aeruginosa. The alga-lysing active components were mainly water-soluble extracellular products, which remained quite stable regardless of exposure to high temperature, pH and ultraviolet radiation. The fermention liquid still showed a high alga-lysing rate, over 95%after being incubated under 60℃ for two hours, over 93.8% at pH 7 - 9, and 85.7% after exposure to 254 nm ultravioletradiation for 2 hours. Based on 16S rRNA sequences, strain JXJ 0071 was identified to be of the genus of Streptomyces, being as high as 99% similar to Streptomyces rectiviolaceus in 16S rRNA gene sequences. However, differences were found between JXJ 0071 and S. rectiviolaceus in physiological and biochemical properties. Further studies should be carried out to determine its exact taxonomic status at the species level.

Key words: actinomycete, Microcystis aeruginosa, alga-lysing activity, Streptomyces, phylogenetic analysis