Isolation and identification of an algae-lysing bacterium and its algicidal effect

Water blooms caused by Microcystis aeruginosa broke out frequently all over the world, which caused serious environmental problems. In this study, an algae-lysing bacterium CA with a strong algicidal effect to M. aeruginosa was isolated from the Taihu Lake, China. Then CA was identified as Aquimonas sp. by morphological features, physiological and biochemical characteristics, as well as phylogenetic analysis of 16S rDNA sequences. The degradation rate of CA against M. aeruginosa cells and chlorophyll a were 100% and 83.9% within ten days, respectively. Algicidal effect of CA was positively correlated with the concentration of bacterial suspensions, while negatively correlated with algal concentration. The bacterial cell of CA had no algicidal effect, but their sterile filtrate could lyse M. aeruginosa significantly, indicating that CA lyse M. aeruginosa by an indirect way of excreting algae-lysing substance. The CA cell displayed algicidal effect when adding a small amount of beef extract, glucose or urea to liquid culture. These results indicated that strain CA had potential for controlling the bloom-forming cyanobacteria in freshwater ecosystems.