Lsolation Of Alginic Acid Decomposing Bacteria And Characteristics Of Physiology In Laminaria Japonica Against Infection

In this study, 12 strains of alginic acid decomposing bacteria in surface of Laminaria japonica were isolated using microbiological methods. Five strains of them exhibited highly infective activity. The changes of ultrastructure , the alteration of the level of polyphenol compounds, reactive oxygen species (ROS)and the activities of polyphenol oxidase in Laminaria japonica against infection of alginic acid decomposing bacteria were investigated. The results showed that:1. 12 strains of alginic acid decomposing bacteria were isolated. Five strains of them which could degrade alginate actively were screened out.2. In the kelp' s ultrastructures, chromatophore was sensitive .whereas mitochondria and nucleolus were stabilized comparatively.3. Early stage of infection by alginic acid decomposing bacteria, the contents of polyphenol compound increased quickly,but the activities of polyphenol oxidase were stabilized. Polyphenol compound was one of important chemical components in Laminaria japonica against infection of alginic acid decomposing bacteria.4. The production of reactive oxygen species in Laminaria japonica during infection of alginic acid decomposing bacteria was demonstrated universally. On early infective stage the production rate of ROS had a close relationship with the infection-resistant activity of Laminaria japonica. With lastingness of infection, the productive rate of reactive oxygen species decreased gradually, and photosynthesis also weakened. The notable decline of ROS production occurred earlier than that of photosynthesis. That showed that its reaction of reactive oxygen species (ROS) was very important in Laminaria japonica against infection of alginic acid decomposing bacteria.