Algicidal Process Of Intracellular Materials From Chitinimonas Prasina LY03 Against Skeletonema Costatum

With the acceleration of the speed of industrialization,the problem of marine pollution has become increasingly prominent,and the issue of red tides is even more severe.As one of the dominant algal blooms,Skeletonema costatum has been widely distributed in the coastal waters of China.It has repeatedly caused red tides and caused serious damage to marine ecology and fish farming.It is imperative to look for environmentally-friendly and effective red tide control methods.Our research group screened and obtained a strain Chitinimonas prasina LY03 which showed high algicidal activity against Skeletonema costat'um.In order to explore the algicidal mechanism,we takes the algicidal material extracted from LY03 as the research object,and explores the morphological changes and biochemical responses of algae under the stress of algicidal substances.The results were mainly as follows:(1)The action of LY03 algicidal substance occurs rapidly and stable.When its concentration is 0.2?g/mL,it can cause serious damage to the algal cells and almost all of them died within 48h.This micro-amount of substance can achieve significant algae-lysing effect in a short time,suggesting that it is a kind of algae-lysing material with potential development value.(2)The micrograph took by scanning electron microscope revealed that the thorns of treated algae cells were broken and divided into individual cells in 3 hours.Afterwards,the cell membrane was broken,and the siliceous shell was opened and the contents flowed out.The micrograph took by transmission electron microscopy showed that the structure of the chloroplast was destroyed and the mitochondrial membrane structure gradually collapsed.Finally,the algae cell turned into only one empty shell.These results showed that the algaecide extracted can effectively kill algal cells.(3)The correlation index of photosynthesis was detected and the results showed that the photosynthetic pigments of the algal cells decreased under the treatment of LY03 algicidal substance,the maximum photosynthetic efficiency and electron transfer rate of the treated group was significantly decreased compared with the control group.It can be seen that the LY03 algicidal substances have a serious impact on the photosynthetic system of algal cells,resulting in it fails to carry out photosynthesis.(4)Under the stress of algicidal substances,the abundance of the macromolecular substances such as protein and sugar in the 'algae cells decreased significantly,the variety of fatty acid species decreased too,but the saturated fatty acid content increased.The antioxidant system reacts quickly.However,because of the long-term oxidative stress,the antioxidant system could not remove excess ROS and lead to breakdown,causing the oxidation of other cellular materials and the increase of the MDA.At last,the cell membrane system was damaged,and resulting in dying.(5)The expression status of photosynthetic genes in the cells was detected by real-time quantitative PCR.The results showed that the genes psbD and rcbS were up-regulated at 3h to prevent the influence of the external environment on the algae cells.The damage to the algae cells was too severe to repair,as a result,the photosynthetic genes of algal cells are almost no expressed.It indicated that the photosynthetic system of the algal cells collapsed and the algae cells could no longer perform photosynthesis.