Research Of A Group Bacterial Community That Lyse Microcystis Aeruginosa

With the increasing of eutrophication, outburst frequency of harmful algal blooms is increasing year by year in the world. Microcystis aeruginosa was a major algae led to water bloom, which not only destroyed the balance of aquatic ecosystems, but also produced large amount of algal toxins and other metabolites that had negative influence on human health, aquatic creatures subsistence and water supply. The physical, chemical and other governance methods had been gradually adopted to prevent the harmful algal blooms, and they had more or less disadvantage.Environment friendly biological methods, especially algicidal microorganisms have been concerned by widespread scholars.In the study, microorganism liquid which had the efficient and stable ability to lyse algae was enriched and screened by co-cultured environment water microorganisms and M. aeruginosa. Using a series of physical and chemical factors,algae-lytic ingredients were preliminarily researched for algicidal microorganism liquid. Bacterial community structure of efficient algicidal solution was analyzed by Macro sequencing method. The main result as follow:1. Construction of the efficient algicidal microorganism liquidIn order to investigate the situation of algae bloom, 10 environmental microbial water samples were collected from seriously algae bloom suburban lakes and ponds in Chonqing. The efficient algicidal microorganism liquid was enriched by co-cultured algae bloom waters with M. aeruginosa. Finally, two groups of strong and stable algicidal microorganism liquid, cq-a and cq-b, were got after enriching and screening repeatedly. Compared to the control group, the color of algae liquid in cq-a and cq-b occurred great changes, and has become yellow, but the control group was strong green.The result showed that most of M. aeruginosa has dead in cq-a and cq-b.2.Analysis of algicidal factorsThe centrifugal treatment of efficient algicidal solution, after centrifuging at 3000 rpm for 5 min, the algicidal substance was precipitated, after centrifuging at 7000 rmp for 5 min, the supernatant lost algicidal ability; membrane filter treatment of algicidal microorganism liquid, the algicidal substance was not able to pass 2 μm membrance;temperature treatment of algicidal microorganism liquid, the algicidal activity was significantly lower after 45℃ water bathing 10 min, and was completely lost after48 ℃ water bathing 10min; antibiotic treatment of efficient algicidal solution, the algicidal ability was not influenced by adding cycloheximide, slight impact by chloramphenicol, and lost by tetracycline, it suggested that algicidal substance was not fungus, the effect of gram-positive bacterium were greater than gram-negative bacterium.Single colonies isolated by LB medium had no significant algicidal activity.This study indicated that algicidal substance of the algicidal microorganism liquid was bacterial community composed of a variety of bacteria.3. Structure analysis of algicidal bacterial communityThrough high throughput sequencing of 16 Sr RNA, the result showed that bacterial community structures of cq-a and cq-b had a certain similarity, especially in the high proportion of groups. Thauera was regarded as the most abundant bacterial genera in cq-a and cq-b. The proportion was 42.33% and 45.12% respectively and have a great similarity in the two samples. The proportion of Rhodobacter respectively was 14.26% and 7.38% in cq-a and cq-b. However, the proportion of Leadbetterella was very similar in the two samples, 1.83% and 1.51% respectively. Growth environment and nutritional condition of the two samples were the exactly same,resulting to the similarly dominant bacteria communities, which might be associated with directional selection. The high proportion bacteria groups played fundamental roles in metabolism and physical cycle of the entire bacterial communities. The differences were also displayed in the structure of bacterial community, which was more significant in bacterial communities of relatively small bacteria groups. Some genera had stronger differences in the two samples, for example, the genus of Algoriphagus, Roseomonas, Acetobacteraceae_unclassified had 56.49 times, 26.86 times, 17.83 times difference between the two samples.