Algicidal bacterium CZBC1 inhibits the growth of Oscillatoria chlorina Oscillatoria tenuis and Oscillatoria planctonica

摘要

Frequent harmful cyanobacteria blooms limit the sustainable development of aquaculture. Algicidal bacteria can efficiently control harmful algae without secondary pollution. The algicidal bacteria CZBC1 can lyse Oscillatoria spp. and other harmful cyanobacteria, but its effector mechanism and algicidal threshold are unknown. In this study, we examined the algicidal effect of CZBC1 on O. chlorina, O. tenuis, and O. planctonica by microscopic enumeration and scanning electron microscopy observation. Then, we examined the alginolytic effects of CZBC1 (concentrations 10³–10⁶ colony forming units (cfu)/mL) on these three species (concentrations 10³–10⁶ cells/mL) to determine the effective concentrations of CZBC1 for Oscillatoria spp. alginolysis. Results showed that CZBC1 can directly lyse O. chlorina and O. tenuis but indirectly lyse O. planctonica. When the initial concentration of CZBC1 was 10⁶ cfu/mL, alginolytic effects were high for all three species at all concentrations, and the alginolytic rate could reach 100% in 3–9 days. When the initial concentration of CZBC1 was lower (10³ cfu/mL), its inhibitory effects were delayed by 2–5 days, but the cell counts were significantly decreased compared with the control, evidencing significant alginolysis. In addition, the higher the concentration of the algicidal bacteria suspension, the more significant the alginolytic effects. Our results indicate that CZBC1 has different alginolytic mechanisms for O. chlorina, O. tenuis, and O. planctonica, and that different initial concentrations of CZBC1 have different alginolytic effects on these algal species.