Isolation And Identification Of The Sponge Immobilized Microbial Algaecide And Algicidal Bacteria And Lysing Characteristics

Many kinds of algae can-lead to water bloom and red tide in the seas, lakes and reservoirs. This phenomenon influences or changes the physical and chemical character of water and then results in aquatic animals and plants perish. Especially, the presence of algae in drinking water source can have a significant impact on the treatment of the water. Algae can produce toxins. The over-multiplication of algae can jam the filter tank, shorten operating circles, increase the back-flushing frequency, and raise the water consumption and running cost. Moreover, algae and their soluble metabolic products are the predecessors of by-products, which are carcinogenic, teratogenic and mutagenic, produced from chlorinating disinfections. Since some of removal of cyanobacterial cells using physical and chemical methods were not ideal, and some resulted in the majority of microcystins entering into the surrounding water after cell lysis and death. The algae-lysing bacteria have been concerned by more and more people as the biological means of preventing and curing of water bloom and red tide. In this study, the removal effects and styles of algae and microcystin by the immobilized biosystem on sponge and the algae-lysing bacterial strains have been studied.1. The treatment effects on eutrophic lake's water with the immobilized biosystem on sponge, as well as the algae removal style, have been studied.(1)The active sludge from sewage treatment plants could be used to treat eutrophic lake's water after 7 days domestication. The removal effects of the immobilized biosystem on algae, microcystin, COD and UV₂₆₀ were excellent. When HRT was 5h, the removal rates were 90%, 94%, 75%, 84%, respectively.(2)There were mostly bacteria and the Ciliata and Sarcodina of protozoan and the Rotifiers of metazoan in the immobilized biosystem. Being decomposed by zoogloea bacteria and preyed by microcreature were the two main styles of algae removal, which included two steps: the first was the absorbance of the zoogloea and the second wasdecomposition of the zoogloea bacteria and the predacity of the microcreature. A fraction of algae which was not absorbed could be directly preyed on by the microcreature preying via the style of "settling food".?The microcystins were difficult to be decomposed completely by the microcreature, but bacteria decomposion was the major stystle.2. Five algae-lysing bacterial strains P01, P03, P05, P07 and P15 were isolated from the biosystem immobilized on sponge. The pathogenesis of the strains were studied by detecting the exotoxin.?Isolating algae-lysing bacteria from the biosystem avoided concentrating a great deal of water sample and spending a long time.?Five algae-lysing bacterial strains did not produce exotoxin.3. The strains were identified by the sequence analysis of 16S rDNA.?The lengthes of the PCR products of these five strains were all 1.5 kb. The sequences obtained in this study are available in GenBank under accession numbers AY964602(strain P01), AY964603(strain P03), AY822613(strain P05), AY822614 (strain P07) and AY822615 (strain PI5).?The DNA sequence similarity searches showed that the strain P01 shares 99.93% and 99.65% sequence homology with two strains of Bacterium, and the strains P03, P05 and P07 share more than 99.7% sequence homology with some strain of Bacillus. The sequence analysis of the 16S rDNA fragment amplified from total DNA of strain PI 5 by PCR showed that it shares 99.7% sequence homology with some strain of Rhodococcus. According to these results, the strain P01 belongs to Bacterium, the strains P03, P05 and P07 to Bacillus and strain PI5 to Rhodococcus in phylogenetic framework of bacterial classification.4. The degradation kinetics of algae-lysing bacteria strains and the lysing modes on Microcystis aeruginosa were studied.?The initial densities of bacteria had a strong influence on the degradation velocity. The higher the start bacterium concentration was, the more obvious the lyticeffect, and the shorter the time to attain the maximum rate of lytic effect. The ideal algae removal effect could be obtained as the minimum concentration of these five strains werelO\ 10\ 10\ 105and 107cells ? mlA?The degradation processes of the five strains on Microcystis aeruginosa accorded with the first-order reaction model when the range of Chla concentration was from 0 to 1500 ug'L'1.?The degradation effects of P05 and P07 strains did not antagonize. When the concentration of Chla was high, the degradation effects of mixed strain excelled that of any single strains. However, with the decreasing of the Chla concentration, this advantage was not clear. When the concentration was less than 180(ag*L"', the degradation effects of mixed culture were consistent with that of strain P07.?The lytic effects on the Microcystis aeruginosa of these five strains did not require physical contact between cells, but depended on the production of extracellular chemicals, which are not proteins.At present, the researches on algae-lysing bacteria have not been given much attention to and are in a start stage domestically. The overseas reports were limited in the isolation of algae-lysing bacteria and its algae-lysing phenomenon and the identification by physiology and biochemistry methods. The identification by the sequence analysis and phylogenetic analysis and the the degradation kinetics have not been involved.The study has important theoretical and practical significances including four aspects. Firstly, the immobilized biosystem on sponge provided an economic and feasible appraoaches of algae and microcystins removal. Secondly, isolating algae-lysing bacteria from the biosystem was of significance to probe a kind of isolation method of quickness and simple and convenient. Thirdly, identification by the sequence analysis of 16S rDNA laid the foundation for the reseach on the relation of algae-lysing bacteria on the basic of molecule biology, and boosted the progress of basic research on the algae-lysing bacteria, and provided the theory and practice for the controlling thewater bloom using the algae-lysing bacteria. Lastly, study on the degradation kinetics and the lysing modes on Microcystis aeruginosa had important scientific and practical significance to the applying of algae-lysing bacteria.