Screening,Algicidal Characteristics And Mechanism Study Of Algae-Lysing Bacterium LG3

Due to the impact of human activities on water bodies,nutrients such as nitrogen and phosphorus continue to enter the water environment,accelerating the process of eutrophication in water bodies.Algae grow rapidly in nutrient rich water bodies,and organic matter is generated much faster than it decomposes.The dissolved oxygen content in the water is reduced,and transparency is significantly reduced,ultimately leading to the destruction of the water ecological environment.Physical and chemical methods are usually used to treat blue-green algae blooms,but both have their own shortcomings.Therefore,biological methods have become the main method for treating eutrophication in water bodies,and most of the organisms used in biological methods are algicidal bacteria that have algicidal effects.In this study,Microcystis aeruginosa was used as the test algal species,and an algal lysing bacterium LG3 was selected from the eutrophication outbreak area of Chaohu Lake.Using strain LG3 as the test algal species.The effects of strain LG3 on the algae lysis efficiency of Microcystis aeruginosa under different growth stages,concentration,culture temperature,p H,and initial concentration of algae solution were studied.To investigate the algicidal mode of strain LG3 and the characteristics of algicidal active substances in its extracellular secretion,and to conduct spectral analysis of algicidal products at different bacterial concentrations.Finally,the growth kinetics,algal lysis kinetics,and nitrogen and phosphorus nutrition kinetics of strain LG3 were systematically studied.The main research results are as follows:1.The strain LG3 is a Gram negative bacterium with a white,round,small,opaque colony with regular edges and a dry surface;Reducible nitrate.The obtained16S r RNA sequence（Gen Bank registration number ON680760）was compared with the known sequence,and the homology between strain LG3 and Alcaligenes aquatilis（MG515168.1）of the genus Alcaligenes reached 99.86%.and based on phylogenetic analysis,it was preliminarily determined that strain LG3 belonged to the genus Alcaligenes.2.When the strain LG3 was in the logarithmic phase,the highest algae dissolution rate was found in the bacterial solution,with an algae dissolution rate of86.1%±1.39%;The higher the concentration of the bacterial solution,the higher the algae dissolution rate,and the algal dissolution rate of the original bacterial solution is90.84%±1.28%;The best effect of algae dissolution was at 30℃,with a dissolution rate of 95.07%±0.85%;When the p H is 8,the effect of algae dissolution is better,and the algae dissolution rate is 89.62%±4.17%;The strain LG3 had a good algal dissolving effect on different initial concentrations of algae solution,with the algal dissolving rates of 83.91%±0.63%in the high concentration group and91.99%±1.90%in the low concentration group,respectively.Based on the analysis results of UV,IR,and three-dimensional fluorescence spectroscopy,it can be seen that the algal lysate contains chemical bonds such as N-H,C-H,CH₂,NH³⁺,C-N,and C-O,and it is preliminarily inferred that the algal lysate is a tryptophan like substance.3.The strain LG3 mainly secretes algae lytic active substances in an indirect manner.The main molecular weight of the algicidal active substance of strain LG3with algicidal effect is less than 3.5 KD;After the extracellular secretion was precipitated with ethanol,the algae dissolution rate in the precipitated group was81.83%±2.43%,which was higher than that in the supernatant group;When the extracellular secretion is at 25℃and p H8,it has a strong algicidal activity,and has a high algicidal effect under different p H conditions.The algicidal active substances have p H stability within a certain range.At higher temperatures,the algicidal effect is not significant,and the thermal stability of the algicidal active substances is poor;The alginolytic active substances of strain LG3 have high antioxidant activity;The algicidal active substance of strain LG3 can enhance SOD activity in a short period of time.4.The growth kinetics of strain LG3 using Microcystis aeruginosa algal solution as a nutrient source conformed to the Polynomial model,and the specific growth rate kinetics of strain LG3 conformed to the univariate linear model;The algal dissolution kinetics of strain LG3 during the algal dissolution process are consistent with Exponential and first-order reaction equation models,both of which can predict and simulate the death process of algal cells under the action of strain LG3 The algal dissolution kinetics of strain LG3 during the algal dissolution process are consistent with Exponential and first-order reaction equation models,the concentration changes of TP and TN in the algal cells and the algal dissolution time during the algal dissolution process satisfy a univariate linear model.Figure[42]table[17]reference[73]...