| Environmental problems is an outcome in the process of industrialization and the rapid development of social economy,which have become an increasingly incisive contradiction.Increasing rates of nutrient supply,much of it manmade,fuels accelerating primary production or eutrophication.An obvious and problematic symptom of eutrophication is rapid growth and accumulations of phytoplankton,leading to discoloration of affected waters.Blooms are a prime agent of water quality deterioration,including foul odors and tastes,deoxygenation of bottom waters(hypoxia and anoxia),toxicity,fish kills,and food web alterations.Toxins produced by blooms can adversely affect animal(including human)health in waters used for recreational and drinking purposes.cyanobacterial blooms have persisted in freshwater systems around the world for centuries and appear to be globally increasing in frequency and severity.Algae and other aquatic organisms are interrelated and interact on each other in a complex aquatic environment.Bacteria and algae are the main forces of primary productivity,occupying an important position in the aquatic ecosystem.Accordingly,it is particularly important to study the mechanism of algal bloom control of bloom.As one of the microbial populations,the algicidal bacteria have the characteristics of wide distribution,large number and strong adaptability.Bacterial diversity and community structure provide a precious theory foundation on study of algicidal bacteria which has great potential in the treatment of algae bloom.Objective:Study on the change of community structure of bacteria in different periods of algal blooms,the relationship between culturable bacteria and Microcystis and identification of new strains,which provides a new basis and theory for the future algae control and provides the basic data for the diversity of freshwater microbes and development of resource.Methods:In this paper,the isolation and purification of culturable bacteria from the water samples in the period of water bloom and non bloom of Lake Taihu and Chaohu were studied and the change of the population structure of isolated strain in different periods of algal blooms were analysed.The differences of Taihu and Chaohu isolates at the level of the phyla and the genus were analyzed and studied.The isolated and purified strains were mixed with cyanobacteria at a ratio of 1/10(v/v),and a batch of bacteria with obvious algicidal effect action was screened by comparison with the control.Compare the efficiency of algicidal effect of six strains of algicidal bacteria,two strains of algicidal bacteria determined.And an isolation witn high efficient algicidal were studied and investigated their algicidal effect on Microcystis aeruginosa.In addition,a new strain were classified and determined by analysis of phenotypic characteristics and genetic characteristics in this study.Result:1.A total of 354 strains were isolated and purified from the algae water samples,collected from Taihu Lake and Chaohu Lake,belonging to 73 genera and 163 species respectively.Taihu Lake and Chaohu separated only 24 species of the same genera,indicating that the two lakes of the flora structure in the species vary greatly.The structure of bacteria in Taihu Lake and Chaohu Lake were compared at the level of species.The two freshwater lakes were mainly composed of Proteobacteria and Bacteroidetes.Firmicutes and Actinobacteria.But in the Chaohu Lake Deinococcus-Thermus can also be isolated.It is found that there is a common phenomenon between Taihu Lake and Chaohu Lake,that Proteobacteria is more likely to be separated during the bloom period than in the non-bloom period,and that the Bacteroidetes is more likely to separated during the non-bloom period than bloom period.And Proteobacteria is more likely to be isolated than Bacteroidetes at any period.The results showed that the dominant genera of the isolates of Taihu Lake could contain 19%of Flavobacterium,11%of Porphyrobacter,9%of Rhizobium,9%of Rhizobium,9%of Erythromicrobium;the dominant genera of the isolates of Chaohu Lake include 24%of Porphyrobacter,17%of Rhizobium,13%of Novosphingobim,13%of Sphingolipid,13%of Sphingomonas and 13%of Aeromonas.At the same time.it can be found that the dominant species of isolates in Taihu Lake include 25%of Flavobacterium,13%of Pseudomonas,8%of Rheinheimera.And the predominant species of isolates consisted of 15%of Sphingomonas,13%of Flavobacterium,10%of Novosphingobium,and 8%of Chryseobacterium.2.59 strains from previous study were screened out algicidal bacteria,16 strains of cyanobacteria showed a strong algicidal effect,including 14 strains of Proteobacteria,1 strains of Bacteroidetes,1 strains of Deinococcus-Thermus.Among them,there were 5 strains of a-Proteobacteria,5 strains of ?-Proteobacteria,4 strains of ?-Proteobacteria.The results showed that the majority of the strains were from the Proteobacteria.At the same time,most of the screened genus were 5 strains of Sphingomonadales and 5 strains ofXanthomonadaceae which were included the algae lysing bacteria C1103.According to the observed,the strains C0518,C0920,C0919,C0915,C1103,C1138 have strongly algae lysing effect.And according to observe its morphology,six strains belonging to different species.Two kinds of highly effective algicidal bacteria,C1103 and strain C1138,were identified by the determination of chlorophyll.Two strains were identified by molecular biology.The results showed that C1103 was Lysobacter capsici,and C1138 was Chitinimonas viridis.These two strains were stained with PHB,and the results showed that the PHB staining of strain C1103 was negative,and the PHB staining of strain C1138 was positive.The results showed that both strain C1103 and strain C1138 acted on the cyanobacteria mainly through the bacteria to inhibit the growth.The results showed that algicidal bacteria C1138 had the best lying effect(above 80%)in adding the algae solution at a volume ratio of 2/30(v/v)against the microcystis aeruginosa 905.3.Cells of strain CH26T were aerobic,Gram-negative,non-motile rods,0.6-0.7?m wide and 1.5-3 ?m long,catalase-and oxidase-positive.Endospores and flagella could not be detected.Colonies were light-yellow,circular,convex and translucent when grown on R2A medium.Strain CH26T showed weak growth at concentrations of 1%(w/v)NaCl,although optimal growth occurred in the absence of NaCl.Growth of strain CH26T was observed at the temperature range of 4-35?with an optimum at 25-30? and pH range of 6.0-9.5(with optimum pH 7.0 for growth).The predominant quinone of strain CH26T detected was Q-10,which is the most frequently identified respiratory quinone in bacteria belonging to the family Sphingomonadaceae.The major polar lipids,contained diphosphatidyl glycerol(DPG),phosphatidyl ethanolamine(PE),phosphatidyl glycerol(PG),unidentified phospholipids(UPL),glycolipids(GL1-3),which were different from other species.Major polar lipids of the members of the family Sphingomonadaceae characteristed by comprising sphingoglycolipid(SGL),DPG.PE and PG and were detected in all studied strians except this novel strain.The fatty acid profile of strain CH26T,contained C18:1 ?7c and/or C18:1?6c(32.1%),C16:lco7c and/or C16:lco6c(23.8%)and C14:0 2-OH(17.8%),was distinguishable from the rest by the content of some fatty acids,while C18:l?7c was predominat in all studied strains.Strain CH26T can stored PHB in the cell.The DNA G+C content was 59.2 mol%.The most similar type strain was Sphingopyxis italica SC13E-S71T with pairwise similarity 94.94%.The 16S rRNA gene sequence-based phylogenetic on analysis of strain CH26T place strain CH26T within the family Sphingomonadaceae.Sequence similarity values with other species of the family lower than to the threshold value of(95%).Phylogenetic analysis based on the 16S rRNA gene showed that CH26T forms a distinct lineage within the members of the family Sphingomonadaceae without any obvious clustering with type strains of related species.This relationship was confirmed in the maximum-likelihood tree and maximum-parsimony.Conclusions:1.There are many kinds of culturable bacteria in Lake Taihu and Chaohu,and 163 kinds of strains were isolated under the experimental conditions,which belong to 73 different genera.The strains isolated from the water bodies of Taihu and Chaohu are similar in structure at the class level,and differ greatly in species structure.2.The chance that Proteobacteria,isolated during the bloom period,was greater than that in the non-bloom period.While the Bacteroidetes was isolated during the non-bloom period was greater than that of the blooms,and the chance that Proteobacteria isolated is greater than Bacteroides at any time.3.The strain CH26T was identified as a new genus and new species of the genus Spingomonadaceae,named Loukaniko chaohuensis gen,Nov.,sp.Nov.,and the numbers of the strains were CGMCC 1.15808 and KCTC 52665.The accession number of strain CH26T 16S rDNA sequence is KX377521.4.In the experiment,16 strains of algicidal bacteria were screened out,and these are signs that most of the strains were from the Proteobacteria.Screening out two highly effective algae strains,and the algae lysing rate of the two strains was higher than 50%agaist FACHB 7942,PCC7806 and FACHB905,and the algae lysing effect was produced by the direct action of the bacteria.The strain C1138 strain had the best effect at the concentration ratio of 2/30,and the algae effeciency was more than 80%on the fourth day. |
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