| Nowdays, eutrophication and massive accumulations of planktonic microalgae as algal blooms in waterbodies have caused serious environmental problems and done harm to the health of people around. So it is important to find out an effective method for controlling the growth of the blooming-forming algae. Measures for controlling such kind of algae include physical, chemical and biological means, but the former two may damage the aquatic environment and require high-energy inputs. The alternative approach for the elimination of nuisance algae involves the application of algae-lysing bacteria. Algae-lysing bacteria as the biology of removing algae have attracted more attention and has broad application prospect.The alage-lysing bacteria are able to restrain the biomass or multiplication of the bloom-forming algae in a short time, especially in the initial stages of the water blooms. Three algae-lysing bacteria named TL1、TL2、TL3 and two algae-lysing bacteria named JZ1 and JZ2 were isolated from water collected in Tai Lake and seafloor sediment collected in Jiaozhou Bay, respectively, and these bacterial strains were identified by physiologically and biochemically. We investigated the lytic abilities and mechanisms of TL1、TL2、TL3 strains and JZ1、JZ2 on the growthes of Microcystis aeruginosa and Skeletonema costatum, respectively. Moreover, we studied the characteristics of extracellular algae-lysing components from bacterial strains.1. Isolation and identification of the bacteria against Microcystis aeruginosa1) Among 24 bacterial strains isolated from water sample of Tai Lake, three bacterial strains, named as TL1、TL2、TL3, showed strong lytic activities. Thus, they were selected to be as research materials.2) The bacterial strains were identified by the sequence analysis of 16SrDNA, and the DNA sequence similarity analysis with the obtained sequences in Genbank. According to the morphological and physiological-biochemical characteristics, strains TL1、TL2、TL3 belong to Achromobacter sp., Slenotrophomonas sp. and Bacillus sp., respectively.2. The lytic abilities and mechanisms of strain TL1、TL2、TL31) Strains TL1、TL2、TL3 were able to restrain the growth of Microcystis aeruginosa、Chlorophyta and Chlorella strongly, and contents of chlorophyll-a and phycocyanin in the algae decreased remarkable, and strain TL1 had the best algicidal activity.2) Comparing to control, the maximal photochemical efficiency of PSⅡ(Fv/Fm), the actual photochemical efficiency of PS II in the light (Yield), the maximal relative electron transport rate (Pm) reduced sharply. The photosynthesis of M. aeruginosa was greatly promoted by three bacterial strains and the growth of M. aeruginosa was inhibited, this was the algicidal mechanisms of strains TL1、TL2、TL3.3) The algae-lysing factors in strains TL1、TL2、TL3 were not the bacterium themselves, but a kind of extracellular products from them. Three bacterial strains had algicidal effects on M. aeruginosa by indirect attack.3. The optimization of fermenting conditions of bacteria and study on the characteristics of algicidal substances1) When incubation temperature was 35℃, pH condition was 8.0 and the incubation time was 96h, the algicidal substance excreted by strain TL1 had the best algicidal effect on M. aeruginosa; and when incubation temperature was 30℃, pH was 7.0, the incubation time was 60h, the algicidal substance excreted by strains TL2 had the best algaicidal effect; the algicidal substance produced by strain TL3 showed the best algicidal effects when incubation temperature was 30℃, pH was 7.0, the incubation time was 72h.2) The algicidal substances excreted by strains TL1, TL2, TL3 lost the algicidal activities under the treatment of Proteinase K, it suggested that the algicidal substances excreted by stain TL1, TL2, TL3 were not protein.3) There were not phosphorous in the algicidal substances, the algicidal substances excteted by strain TL1, TL2, TL3 were not nucleic acid.4) The molish of strain TL1 and TL3 were negative, so the algicidal substances excreted by strain TL1 and TL2 were not sugar, they may be other substances; the algicidal substance of strain TL3 was water-soluble sugar.4. Isolation and identification of bacteria against Skeletonema costatum1) Two bacterial strain which showed lytic effects on Skeletonema costatum were isolated from seafloor sediment that collected in Jiaozhou Bay. And they were named provisionally as JZ1 and JZ2.2) Strains TL1 and TL2 belong to Alteromonas sp. and Maribacter sp., respectively, on the basis of morphological and physiological-biochemical characteristics.5. The lytic abilities and mechanisms of strain JZ1、JZ21) When the volume ratio of medium to algae solution was 10%, the cells of S.costatum died absolutely after 10 days.2) After addtion of strain JZ1, cellular morphology changes with time. Condensation of the cells and chloroplasts was clearly visible as was the formation and release of membrane blebs. So the algicidal mechanisms of strain JZ1、JZ2 are because the strains could break the cells of S. costatum, and this is indicative of programmed cell death.3) The antialgal efficiencies of JZ1 and JZ2 were different to the various growth phages of algae. For strain JZ1, the removal rate of S. costatum in stable phrase was the highest, and the next was log growth phase. However, strain JZ2 showed obvious algicidal effect in all growth phases of S. costatum.4) The algae-lysing factors in strain JZ1, JZ2 were not the bacterium themselves, but a kind of extracellular products from them as stain TL1, TL2, TL3. The two bacterial strains had algicidal effects on S. costatum by indirect attack.5) Species of Isochrysis galbana, Dunaliella salina were susceptible to bacterium JZ1,while the lytic effects of this bacterium on Tetraselmis chui, Pavlova lutheri, Nannochloropsis salina, Tetraselmis suecica, Thalassiosira pseudonana were feeble.6) Strain JZ2 had effects on the growth of Pavlova lutheri and Isochrysis galbana, but didn’t show effects on Tetraselmis chui, Dunaliella salina, Nannochloropsis salina, Tetraselmis suecica, Thalassiosira pseudonana. 6. Isolation and purification of algicidal substance from strain JZ11) The algicidal substance of strain JZ1 showed a little bit effect on the growth of S. costatum with acid treatment, but that of strain JZl lost the algicidal activity under stresses with alkali or high temperature; Strain JZ2 had acid tolerance and showed obvious effect on the growth of S. costatum.2) The pure algicidal substance of strain JZ1 was got, with the isolation and purification of resins and HPLC.3) Depend on the analysis of LC-ESI-MS and MALDI-MS, the algicidal component of strain JZ2 was a peptide with 1267kDa molecular weight.As above, the excretes produced by strains TL1、TL2、TL3 inhibit the growth of Microcystis aeruginosa by hindering the photosynthesis of M. aeruginosa; the excretes procuced by strains JZ1、JZ2 inhibit the growth of Skeletonema costatum by destroying the cells of S. costatum. The biological algaecide that made from the algicidal substances produced by algae-lysing bacteria have broad application prospect, based on the analysis of algicidal characteristics and algicidal mode of 5 strains of algae-lysing bacteria and the study characteristics of algicidal substances. |
PDF Full Text Request