Isolation Of Two Algicidal Bacteria Of Marine Eukaryotic Algae And Their Algicidal Characteristic

Using marine eukaryotic algae as the experimental material, two novel algicidal bacteria named XD-G and XD-J were isolated from the water of XiangShan Bay in NingBo.The algicidal effect of the bacteria XD-G against S. costatum 1115 was significant: almost all of the algal cells were lysed in 24 hours, and the concentration of Chl.a was reduced by 66.5% then. By electron microscope observation, a large number of the bacteria could be observed in S. costatum cells after 9 hours' infection, which means that the bacterium XD-G is a kind of parasitic bacterium. Furthermore, the bacteria XD-G could not only lyse S. costatum 1115 and Skeletonema troicum, but also removed Heterosigma akashiwo. There was no report about the parasitic bacteria of S. costatum, so the bacterium XD-G is a novel parasitic algicidal bacterium.The algicidal effect of the bacteria XD-J against Isochrysis galbana was significant: the concentration of Chl.a was reduced by 76.4% after 4 days' infection. The culture of bacteria XD-J filtered by the membrane filter of 0.22μm, and its filtrate was added into the culture of I. galbana, however, there was no algicidal phenomenon. By electron microscope observation, there were no bacteria in I. galbana Cells, which means that the bacterium XD-J is a kind of bacterium which can lyse I. galbana for the direct contact with the algal cells. But it did not eliminate the possibility that the bacteria XD-J competed with algal cells for the nutrients. The bacterium XD-J has poor heat-tolerant, and the maximum tolerable temperature is between 40℃and 50℃. The bacteria XD-J only could lyse I. galbana.