Purification Of Axenic Microcystis And The Study Of Relationship Of Microcystis And Bacteria

In this study, Microcystis aeruginosa905 for material, was found difficult to remove bacteria carried by itself. Basing on the study of growth of algae, using the method of capillary picking and alternated culturing by agar and liquid medium, axenic Microcystis strains 905A were isolated, and according to the 16SrDNA sequencing, the genus was identified as Microcystis and either only 93% similarity with two strains of Microcystis aeruginosa843and 7806, 100% similarity with a strain of uncultured Microcystis,which was just identified as Microcystis sp.The relation of Microcystis aeruginosa905 and bacteria was studied by changing the growth conditions of strains, and a close relationship of bacteria and Microcystis was found. It shows that the strains could stimulate and promote each other. When bacteria B905-1 does not exist, Microcystis905 can not split and grow in agar medium and it can not grow in the liquid medium when its concentration is less than 102/ ml. In the presence of bacteria B905-1, about 30% of the single alga cells could grow in agar medium, as well as in the liquid medium with the concentration less than 102/ml. The effect that tpiphytic bacteria B905-1 makes on the Microcystis is directly, and the sterile filtrate does not work. When the external substance such as organic,beef extract medium,or epiphytic bacteria was added directly, the number of bacteria was 70 times much bigger than that in the natural state in liquid medium, or the proportion of alga and bacteria reached to 1:1 in agar medium, epiphytic bacteria could obtain nutrition by cracking Microcystis.It was found that the Microcystis 905A and Microcystis 905 respond differently to the adding of organic matters in this study. 2% beef extract medium could cracke Microcystis 905 while has no effect on the axenic Microcystis 905A.Bacillus T1 was isolated from surrounding soil of Wuhan, and its suppression rate on Microcystis 905 can reach to 97%. After selective experiments, the 4th medium was selected as the fermentation medium,and the suppression rate of Microcystis -905 was up to 95.7% when the fermentation was carried under 37℃. After tests, Microcystis 905A and Microcystis 905 could either be cracked by sterile filtrate of Bacillus,but the effect on Microcystis905A was more obvious than the Microcystis 905. After 16SrDNA sequencing and morphological observation, the strain T1 was identified as Bacillus subtilis or Bacillus amyloliquefaciens. It shows that the active substances producted by T1 exist mainly in the sterile filtrate,and it is tolerant to the temperature121℃.Substances fermented by T1 could promote the growth of Chlorella,and not poison mice in the test of toxicology.A number of other lytic substances,like corn syrup and streptomyces were studied, and lytic mechanism was researched preliminarily.