The objective of this study was to isolate algae growth inhibiting microorganism to biologically control Microcystis
aeruginosa, which is a harmful cyanobacterium. Various bacterial strains were isolated in this study, and four
bacterial strains of M1~M4 exhibited remarkable growth inhibiting activity against M. aeruginosa. Based on the 16S
rRNA analysis, the isolated M1~M4 strains were identified, and isolated four strains were rod-type and
gram-negative. In particular, as well as respective single strain, co-culture of the isolated M1~M4 strains showed
obvious algicidal activity against M. aeruginosa. When mixed four strains were inoculated, about 50% of the
chlorophyll a was reduced after two days, about 70% after four days, and about 80% after seven days. From these
results mentioned above, the four bacterial strains may contribute to the control of harmful M. aeruginosa.