Magnetotactic bacterium MSR-1 strain as well as culture medium, culture method and application thereof

Abstract

The invention provides a magnetotactic bacterium MSR-1 strain as well as a culture method and application of the magnetotactic bacterium MSR-1 strain, and belongs to the technical field of environmental microorganisms. The invention provides a magnetotactic bacterium MSR-1 strain, and the preservation number of the magnetotactic bacterium MSR-1 strain is CCTCC (China Center for Type Culture Collection) NO: M 20242494. By optimizing culture conditions of magnetotactic bacteria MSR-1 strains, including adjusting key factors such as different carbon sources, different nitrogen sources, different iron sources and different types of reducing agents, the biomass and the magnetic production activity of the MSR-1 are synchronously improved. The invention further provides application of the magnetotactic bacterium MSR-1 strain in bioremediation of cadmium-polluted water and soil, and a new thought is provided for solving the increasingly serious heavy metal pollution environment problem.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental microorganisms, and in particular relates to a magnetotactic bacteria MSR-1 strain and a culture medium, a culture method and an application thereof. Background Art

[0002] Heavy metal pollution in the environment comes from a wide range of sources, including wastewater discharge from metallurgy, mineral mining, electronic product production, electroplating, and chemical industries, as well as sewage and sludge irrigation, and the application of insecticides, pesticides, and fertilizers. Among the many heavy metal pollutions, cadmium (Cd) pollution is the primary problem. According to the "National Soil Pollution Status Survey Bulletin", cadmium has the highest point-to-point rate of exceeding the standard, and more than 40% of the heavy metal compound-contaminated soils have cadmium pollution. Cadmium is one of the most easily accumulated harmful substances in organisms known to date, with a half-life of 10 to 30 years. Human activities have led to an increasing content of cadmium in the environment and an increasing distribution range. When heavy metal pollutants enter the natural environment, they will be absorbed by animals and plants, and gradually accumulate in the organs and tissues of animals and the roots, stems, leaves, and fruits of plants, and eventually affect human health through the food chain. Therefore, the restoration of cadmium-contaminated water and soil is of great significance for protecting the ecological environment and human health.

[0003] At present, there are three main types of remediation methods for heavy metals in soil and other environments at home and abroad. The first is physical remediation, such as removing topsoil, importing soil and leaching. The advantage of this remediation method is that it can quickly achieve stable remediation, but it has obvious shortcomings, that is, it requires a lot of financial and human resources, which makes it not suitable for large areas of pollution. The second is chemical remediation, which is to add some chemical additives to the soil to change the form of heavy metals in the soil and reduce its biological effectiveness. The prevention and control effect of this method for cadmium pollution is at a medium level, but once the environmental conditions change, cadmium may be activated again. The third is biological remediation, which mainly covers various forms such as plant remediation technology and microbial remediation technology. It uses certain characteristics of the organism itself to absorb, degrade, transform, inhibit and improve heavy metal pollution. Bioremediation has become a research hotspot in the field of soil heavy metal remediation because it adheres to the concept of ecological protection and economy. Compared with traditional physical-chemical remediation methods, bioremediation technology is more suitable for in-situ remediation of non-point source heavy metal contaminated soils. It also has a series of advantages such as low cost, environmental protection, simple operation, and low secondary pollution. Among them, microbial remediation technology has received widespread attention. Microorganisms can remove heavy metals from the environment or convert them into less toxic forms through processes such as adsorption, enrichment and transformation. However, separating and recovering these microorganisms with specific functions from environmental media is still a huge challenge.

[0004] At present, at home and abroad, the research on using microorganisms as environmental heavy metal pollution control and remediation agents has a certain foundation. Magnetotactic bacteria is a general term for a class of microorganisms that can move along the direction of the magnetic field. There are abundant species of magnetotactic bacteria in nature. Studies have used the characteristics of magnetotactic bacteria to remove heavy metals such as Ag and Cu from water bodies. However, there is no public application of the MSR-1 strain of magnetotactic bacteria for the remediation of cadmium pollution in water or soil. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a magnetotactic bacteria MSR-1 strain and its culture medium, culture method and application, by optimizing the culture medium and culture conditions of the magnetotactic bacteria MSR-1 strain, simultaneously improving its biomass and magnetic activity, and ultimately using it to repair water and soil contaminated by heavy metal cadmium.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a magnetotactic bacterium ( Magnetospirillum gryphiswaldense ) MSR-1 strain, the deposit number of the magnetotactic bacteria MSR-1 strain is CCTCC NO: M 20242494.

[0007] The present invention provides a culture medium for culturing the magnetotactic bacteria MSR-1 strain, wherein the carbon in the culture medium As an embodiment, the amount of carbon source added to the culture medium is 2-5 g / L, the amount of nitrogen source added is 0.2-0.5 g / L, the amount of iron source added is 0.005-0.02 g / L, and the amount of reducing agent added is 0.03-0.06 g / L.

[0008] Preferably, the culture medium comprises 3-4 g / L sodium lactate, 0.35-0.50 g / L ammonium chloride, 0.010-0.015 g / L ferric citrate and 0.045-0.060 g / L sodium thioglycolate.

[0009] The present invention also provides a method for culturing the aforementioned magnetotactic bacteria MSR-1 strain, comprising the following steps: inoculating the activated magnetotactic bacteria MSR-1 into the aforementioned culture medium, and culturing for 18 to 48 hours at 25 to 35° C. and 90 to 120 r / min.

[0010] Preferably, the culturing time is 20 h to 36 h.

[0011] The present invention also provides a preparation product, which comprises the aforementioned magnetotactic bacteria MSR-1 strain.

[0012] The present invention also provides the use of the aforementioned preparation product of the magnetotactic bacteria MSR-1 strain in repairing cadmium pollution, including repairing cadmium pollution in water bodies and / or repairing cadmium pollution in soil.

[0013] As an implementation mode, during the remediation, the pH of the water body or the soil is adjusted to 5.0-8.0, and the initial cadmium concentration is below 2 mg / L.

[0014] In the present invention, the inoculation amount of the magnetotactic bacteria MSR-1 in the water body is 3 to 10 g / L. The remediation soil is mixed with water to prepare a water-soil mixture, and the magnetotactic bacteria MSR-1 is inoculated in the water-soil mixture at an inoculation amount of 3% to 5% of the soil mass.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a magnetotactic bacterium ( Magnetospirillum gryphiswaldense ) MSR-1 strain and its culture medium, culture method and application. The present invention takes the magnetotactic bacteria MSR-1 strain as the core research object, deeply explores the effects of key factors such as different types of carbon sources, nitrogen sources, iron sources and reducing agents and addition amounts on the magnetotactic bacteria MSR-1, and designs a culture medium and culture conditions that can simultaneously improve the biomass and magnetic activity of MSR-1 through a large number of fine experiments and data analysis, thereby realizing the efficient utilization of the magnetotactic bacteria MSR-1 strain. On this basis, the present invention provides a preparation product prepared by the magnetotactic bacteria MSR-1 strain, further expanding the application scope of the magnetotactic bacteria MSR-1 strain and the preparation product in the field of heavy metal cadmium pollution control, and applying it to the practice of cadmium-contaminated water and soil remediation. The present invention utilizes the unique physiological characteristics of the MSR-1 strain and regulates the external environmental conditions, and can effectively adsorb and remove the cadmium element in the polluted water or soil with an initial cadmium concentration of 2 mg / L, thereby realizing the effective remediation of heavy metal cadmium-contaminated water and soil, and, with the help of magnetic adsorption technology, realizes the efficient recovery of the remediation agent, effectively avoiding the generation of secondary pollution problems. The present invention provides a high-efficiency, low-cost and environmentally friendly method for the bioremediation of cadmium-contaminated water and soil, and is of great significance for solving the increasingly serious environmental problem of heavy metal pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Scanning electron micrograph of the magnetotactic bacteria strain MSR-1.

[0017] Figure 2 Effects of different carbon sources, nitrogen sources, iron sources and reducing agents on the cultivation of magnetotactic bacteria MSR-1 strain.

[0018] Figure 3Three-dimensional response surface optimization reaction diagram of the interactive effect of sodium lactate and ammonium chloride addition on MSR-1 bacterial concentration, A: sodium lactate addition; B: ammonium chloride addition; C: ferric citrate addition of 0.0125 g / L; D: sodium thioglycolate addition of 0.045 g / L.

[0019] Figure 4 Three-dimensional response surface optimization reaction diagram of the interactive effect of sodium lactate and ferric citrate addition on MSR-1 bacterial concentration, A: sodium lactate addition; B: ammonium chloride addition of 0.35 g / L; C: ferric citrate addition; D: sodium thioglycolate addition of 0.045 g / L.

[0020] Figure 5 Three-dimensional response surface optimization reaction diagram of the interactive effect of sodium lactate and sodium thioglycolate addition on MSR-1 bacterial concentration, A: sodium lactate addition; B: ammonium chloride addition of 0.35 g / L; C: ferric citrate addition of 0.0125 g / L; D: sodium thioglycolate addition.

[0021] Figure 6 Three-dimensional response surface optimization reaction diagram of the interactive effect of ammonium chloride and ferric citrate addition on MSR-1 bacterial concentration, A: sodium lactate addition amount is 3.5 g / L; B: ammonium chloride addition amount; C: ferric citrate addition amount; D: sodium thioglycolate addition amount is 0.045 g / L.

[0022] Figure 7 Three-dimensional response surface optimization reaction diagram of the interactive effect of ammonium chloride and sodium thioglycolate addition on MSR-1 bacterial concentration, A: sodium lactate addition amount is 3.5 g / L; B: ammonium chloride addition amount; C: ferric citrate addition amount is 0.0125 g / L; D: sodium thioglycolate addition amount.

[0023] Figure 8 Three-dimensional response surface optimization reaction diagram of the interactive effect of ferric citrate and sodium thioglycolate addition on MSR-1 bacterial concentration, A: sodium lactate addition amount is 3.5 g / L; B: ammonium chloride addition amount is 0.35 g / L; C: ferric citrate addition amount; D: sodium thioglycolate addition amount.

[0024] Fig. 9 Three-dimensional response surface optimization reaction diagram of the interactive effect of sodium lactate and ammonium chloride addition on the amount of MSR-1 magnetosome formation, A: sodium lactate addition; B: ammonium chloride addition; C: ferric citrate addition of 0.0125 g / L; D: sodium thioglycolate addition of 0.045 g / L.

[0025] Fig.10Three-dimensional response surface optimization reaction diagram of the interactive effect of sodium lactate and ferric citrate addition on the amount of MSR-1 magnetosome formation, A: sodium lactate addition; B: ammonium chloride addition of 0.35 g / L; C: ferric citrate addition; D: sodium thioglycolate addition of 0.045 g / L.

[0026] Fig.11 Three-dimensional response surface optimization reaction diagram of the interactive effect of sodium lactate and sodium thioglycolate addition on the amount of MSR-1 magnetosome formation, A: sodium lactate addition; B: ammonium chloride addition of 0.35 g / L; C: ferric citrate addition of 0.0125 g / L; D: sodium thioglycolate addition.

[0027] Fig.12 Three-dimensional response surface optimization reaction diagram of the interactive effect of ammonium chloride and ferric citrate addition on the amount of MSR-1 magnetosome formation, A: sodium lactate addition amount is 3.5 g / L; B: ammonium chloride addition amount; C: ferric citrate addition amount; D: sodium thioglycolate addition amount is 0.045 g / L.

[0028] Fig.13 Three-dimensional response surface optimization reaction diagram of the interactive effect of ammonium chloride and sodium thioglycolate addition on the amount of MSR-1 magnetosome formation, A: sodium lactate addition amount is 3.5 g / L; B: ammonium chloride addition amount; C: ferric citrate addition amount is 0.0125 g / L; D: sodium thioglycolate addition amount.

[0029] Fig.14 Three-dimensional response surface optimization reaction diagram of the interactive effect of ferric citrate and sodium thioglycolate addition on the amount of MSR-1 magnetosome formation, A: sodium lactate addition amount is 3.5 g / L; B: ammonium chloride addition amount is 0.35 g / L; C: ferric citrate addition amount; D: sodium thioglycolate addition amount.

[0030] Fig.15 Growth curve and C of magnetotactic bacteria strain MSR-1 under the optimal conditions optimized by response surface analysis mag curve.

[0031] Fig.16 Different pH values, Cd 2+ Effects of initial concentration, MSR-1 biomass concentration and temperature on the adsorption of Cd by magnetotactic bacteria MSR-1 2+ Effect of efficiency, (a) pH; (b) Cd 2+ Initial concentration; (c) MSR-1 biomass concentration; (d) temperature.

[0032] Fig.17 Magnetotactic bacteria MSR-1 to Cd 2+ Adsorption kinetics and adsorption isotherm analysis, (a) adsorption kinetics analysis, (b) adsorption isotherm analysis.

[0033] Fig.18 Cadmium removal effect of magnetotactic bacteria MSR-1 on cadmium-contaminated water.

[0034] Fig.19 Pollution reduction and remediation effect of magnetotactic bacteria MSR-1 strain on different Cd-contaminated soils, * represents p < 0.05, ** represents p < 0.01.

[0035] Biological Deposit Description Magnetotactic bacteria ( Magnetospirillum gryphiswaldense ) MSR-1, deposited in the China Center for Type Culture Collection on November 8, 2024, with the deposit number CCTCC NO: M 20242494. The address of the depository unit is Wuhan University, No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province. DETAILED DESCRIPTION

[0036] The present invention provides a magnetotactic bacterium ( Magnetospirillum gryphiswaldense ) MSR-1 strain, the deposit number of the magnetotactic bacteria MSR-1 strain is CCTCC NO: M 20242494. The magnetotactic bacteria MSR-1 belongs to the class α-Proteobacteria and is derived from freshwater sediments.

[0037] In the present invention, a culture medium of the magnetotactic bacteria MSR-1 strain is provided, wherein the source in the culture medium includes sodium lactate, the nitrogen source includes ammonium chloride or ammonium sulfate, the iron source includes one of ferrous sulfate, ferric citrate, ferric quinate and compound iron (ferrous sulfate and ferric citrate are compounded in a ratio of 1:1), and the reducing agent includes one of sodium thioglycolate, ascorbic acid and cysteine. In the present invention, the activated magnetotactic bacteria MSR-1 strain is inoculated in a culture medium containing different types of carbon sources, nitrogen sources, iron sources and reducing agents, and the optimal conditions for the biological status and magnetism production ability of the magnetotactic bacteria MSR-1 are screened. Preferably, the carbon source is sodium lactate. Preferably, the nitrogen source is ammonium chloride. Preferably, the iron source is ferric citrate. Preferably, the reducing agent is sodium thioglycolate. In the present invention, the addition amount of different types of carbon sources, nitrogen sources, iron sources and reducing agents is also considered. Specifically, the addition amount of carbon source in the culture medium is 2-5 g / L, the addition amount of nitrogen source is 0.2-0.5 g / L, the addition amount of iron source is 0.005-0.02 g / L, and the addition amount of reducing agent is 0.03-0.06 g / L. Preferably, the carbon source in the culture medium is sodium lactate, and the addition amount is 2-5 g / L; the nitrogen source is ammonium chloride, and the addition amount is 0.2-0.5 g / L; the iron source is ferric citrate, and the addition amount is 0.005-0.02 g / L; the reducing agent is sodium thioglycolate, and the addition amount is 0.03-0.06 g / L. In further preferred embodiments, the culture medium comprises 3-4 g / L sodium lactate, 0.35-0.50 g / L ammonium chloride, 0.010-0.015 g / L ferric citrate and 0.045-0.060 g / L sodium thioglycolate. In further preferred embodiments, the culture medium comprises 3.38 g / L sodium lactate, 0.50 g / L ammonium chloride, 0.011 g / L ferric citrate and 0.060 g / L sodium thioglycolate.

[0038] In the present invention, a method for culturing the aforementioned magnetotactic bacteria MSR-1 strain is provided, comprising the following steps: inoculating the activated magnetotactic bacteria MSR-1 in a culture medium containing a carbon source, a nitrogen source, an iron source and a reducing agent, and culturing for 18 to 48 hours at 25 to 35°C and 90 to 120 r / min. In the present invention, the activation process is to take the magnetotactic bacteria MSR-1 strain out of the frozen glycerol strain, inoculate it in a magnetotactic bacteria liquid culture medium, place it in a shaker at 30°C, and culture it at 110 r / min for 24 hours until the OD 565The value reaches 0.6. In the present invention, the magnetotactic bacteria liquid culture medium includes 0.01-0.02 g / L of ferric citrate, 0.05-0.15 g / L of yeast powder, 0.30-0.60 g / L of potassium dihydrogen phosphate, 0.30-0.50 g / L of ammonium chloride, 0.05-0.20 g / L of magnesium sulfate, 2.5-4.0 g / L of sodium lactate, 0.04-0.07 g / L of sodium thioglycolate and 0.005-0.2% of trace elements. In the present invention, the trace elements include 1.20-1.70 g / L nitrilotriacetic acid, 2.6-3.2 g / L MgSO4·7H2O, 0.3-0.7 g / L MnSO4·H2O, 0.8-1.3 g / L NaCl, 0.05-0.14 g / L FeSO4·7H2O, 0.05-0.14 g / L CoCl2·6H2O, 0.05-0.14 g / L CaCl2, 0.05-0.14 g / L ZnSO4·7H2O, 0.0080-0.014 g / L CuSO4·5H2O, 0.0080-0.014 g / L AIK(SO4)2·12H2O, 0.0080-0.014 g / L g / L H3BO3, 0.0080-0.013 g / L Na2MoO4·2H2O. Preferably, the trace elements include 1.5 g / L nitrilotriacetic acid, 3.0 g / L MgSO4·7H2O, 0.5 g / L MnSO4·H2O, 1.0 g / L NaCl, 0.1 g / L FeSO4·7H2O, 0.1 g / L CoCl2·6H2O, 0.1 g / L CaCl2, 0.1 g / L ZnSO4·7H2O, 0.01 g / L CuSO4·5H2O, 0.01 g / L AIK(SO4)2·12H2O, 0.01 g / L H3BO3, and 0.01 g / L Na2MoO4·2H2O. Preferably, the magnetotactic bacteria liquid culture medium includes 0.01 g / L ferric citrate, 0.10 g / L yeast powder, 0.5 g / L potassium dihydrogen phosphate, 0.4 g / L ammonium chloride, 0.10 g / L magnesium sulfate, 3 g / L sodium lactate, 0.05 g / L sodium thioglycolate and 0.1% trace elements. In the present invention, the magnetotactic bacteria liquid culture medium is prepared by adding the above-mentioned components to deionized water, adjusting the pH and sterilizing with high pressure steam. In the present invention, one or more of dilute hydrochloric acid, phosphoric acid and citric acid are selected to adjust the pH. Preferably, dilute hydrochloric acid is selected to adjust the pH. The concentration of the dilute hydrochloric acid is 0.5-2 mol / L. Further preferably, the concentration of the dilute hydrochloric acid is 1 mol / L. The pH is 6-8. Preferably, the pH is 6-7. Further preferably, the pH is 6.98.In the present invention, the optimized magnetotactic bacteria MSR-1 is cultured in a shaking incubator at 25 to 35°C at 90 to 120 r / min for 18 to 48 hours. Preferably, the culture temperature is 30°C and the shaking speed is 110 r / min. Preferably, the culture time is 20 to 36 hours. More preferably, the culture time is 24 hours. The present invention determines the optimal conditions for the biological condition and magnetic production capacity of the magnetotactic bacteria MSR-1 by optimizing and adjusting the above key factors.

[0039] The present invention also provides a preparation product, which is prepared from the magnetotactic bacteria MSR-1 strain with a deposit number of CCTCC NO: M20242494. In the present invention, the preparation product also preferably includes excipients. The present invention has no special restrictions on the type of the excipients, and biological preparation excipients well known in the art can be used, and water or magnetotactic bacteria liquid culture medium can be selected. The present invention has no special restrictions on the preparation method of the product, and the preparation scheme of bacterial products well known in the art can be used, for example, the expanded culture of the magnetotactic bacteria MSR-1 strain bacterial liquid is mixed with excipients.

[0040] The present invention also provides the use of the aforementioned magnetotactic bacteria MSR-1 strain or a preparation product containing the magnetotactic bacteria MSR-1 strain in the repair of cadmium pollution, including repairing cadmium pollution in water bodies and / or repairing cadmium pollution in soil. In the present invention, when the magnetotactic bacteria MSR-1 strain or the preparation product containing the magnetotactic bacteria MSR-1 strain is used, the pH of the water body or the soil should be adjusted to 5.0-8.0. Preferably, the pH is 8.0. One or more of hydrochloric acid, citric acid, sodium hydroxide, and sodium bicarbonate can be used to adjust the pH, but it is not limited to the above. A high concentration of heavy metal cadmium will have a toxic effect on bacteria and cause bacterial cell damage, so it is necessary to set the initial concentration of cadmium-contaminated water. In the present invention, the initial concentration of cadmium in the cadmium-contaminated water body is between 0 and 5 mg / L. Preferably, the initial concentration of cadmium is 0-2 mg / L. More preferably, the initial concentration of cadmium is 0.5-2 mg / L. Still more preferably, the initial concentration of cadmium is 2 mg / L. In the application of repairing cadmium pollution, the inoculation amount of the magnetotactic bacteria MSR-1 in the water body is 3 to 10 g / L. Preferably, the inoculation amount of the magnetotactic bacteria MSR-1 in the water body is 3 to 7 g / L. More preferably, the inoculation amount of the magnetotactic bacteria MSR-1 in the water body is 3 to 4 g / L. In the present invention, the application of repairing cadmium pollution in water bodies specifically includes the following steps: detecting the initial cadmium concentration of the polluted water body, adjusting the initial cadmium concentration of the water body to maintain it at 0 to 5 mg / L. Adjust the pH and temperature of the polluted water body, inoculate the magnetotactic bacteria MSR-1 or the preparation product into the polluted water body at an inoculation amount of 3 to 10 g / L, stir the polluted water body after inoculation, and then let it stand for 1 to 2 hours. Afterwards, apply a magnetic field outside the polluted water body for magnetic absorption treatment, separate the sewage from the bacteria without disturbing the bacteria enriched by the side wall magnetic field, and achieve the removal of heavy metal cadmium in the sewage. Wherein, the temperature is 20 to 37°C. Preferably, the temperature is 30°C. After inoculating magnetotactic bacteria, the standing time is 1 to 2 hours. Preferably, the standing time is 1 hour. The magnetic absorption treatment includes magnetic absorption for 18 to 30 hours. The present invention also provides an application for repairing cadmium pollution in soil, which specifically includes the following steps: crushing and grinding cadmium-contaminated soil, adding soil and water to water according to a mass ratio, stirring evenly to obtain a water-soil mixture, inoculating magnetotactic bacteria MSR-1 or a preparation product into the water-soil mixture at an inoculation amount of 3% to 15% of the soil mass, stirring the inoculated water-soil mixture evenly, standing for 1 to 2 hours, applying a magnetic field outside the water-soil mixture, and performing magnetic absorption treatment. Without disturbing the sidewall magnetically enriched bacteria, the water body, soil and bacteria are separated to achieve the removal of heavy metal cadmium in the soil. Wherein, the mass ratio of soil to water is 1: (8 to 12). Preferably, the mass ratio of soil to water is 1: 10.In the present invention, the mass concentration of cadmium in the soil is detected by acid digestion of the soil, and the soil sample is digested with a graphite furnace digestion instrument (SPH-3, Yuanxi Instrument, Shanghai). The digestion procedure and the like are not particularly limited, and the schemes known in the art can be used. The mass concentration of cadmium is detected by inductively coupled plasma mass spectrometry (ICP-MS) (PE Nexion2000, USA), and the detection method is not particularly limited, and the schemes known in the art can be used.

[0041] The present invention applies the magnetotactic bacteria MSR-1 strain or a preparation product containing the magnetotactic bacteria MSR-1 strain to the remediation of cadmium pollution, and takes anhydrous CdCl2 with different mass concentrations to simulate cadmium-containing industrial wastewater, soil in a certain place in Changsha, Hunan, and soil in a certain place in Baiyin, Gansu as examples to verify the cadmium removal ability of the magnetotactic bacteria MSR-1 strain. The results show that the magnetotactic bacteria MSR-1 strain or the preparation product containing the strain used in the present invention can effectively reduce the content of cadmium ions in the water body, and can make the cadmium element removal rate in the water body reach 92.2%, showing excellent cadmium removal and reduction repair potential. When repairing cadmium pollution in the soil, the magnetotactic bacteria MSR-1 strain or the preparation product containing the strain can reduce the total cadmium content of the soil in Changsha and Baiyin by 12.7% and 15.6%, respectively, and also shows good cadmium removal and reduction repair potential.

[0042] The data in the present invention were sorted and analyzed using Microsoft Excel 2019, and one-way analysis of variance (ANOVA) was performed using SPSS 27.0. A significant difference was defined when P < 0.05, and Origin 2023 software was used for drawing the graph.

[0043] In the following embodiments, unless otherwise specified, all of them are conventional methods.

[0044] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0045] The technical solution provided by the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0046] Example 1 Surface morphology of magnetotactic bacteria MSR-1 The bacterial solution was centrifuged at 3040 g for 15 min, the supernatant was discarded, 2.5% glutaraldehyde solution was added to the bacterial precipitate and the bacterial cells were fixed at 4°C for 12 h, then washed twice with 0.01 mol / L sterile PBS buffer, and the washed cells were placed in 50%, 75%, 90% and 100% ethanol solutions for dehydration for 15 min. The cells were freeze-dried and observed using a scanning electron microscope (Zeiss sigma300, Zeiss, Germany).

[0047] The results are as follows Figure 1 As shown, the magnetotactic bacteria MSR-1 cells are spiral-shaped, with a size of approximately 2.0×0.3 μm and an intact cell surface.

[0048] Example 2 Cultivation of magnetotactic bacteria MSR-1 and optimization of magneto-producing conditions 1.1 Optimization of single factor conditions for magnetotactic bacteria strain MSR-1 The magnetotactic bacteria MSR-1 strain was taken out from the frozen glycerol stock, activated and cultured in a magnetotactic bacteria liquid culture medium, and cultured in a shaker (110 r / min, 30°C) for 24 h. Then, it was inoculated in culture media with different carbon sources (sodium acetate, tartaric acid, succinic acid and sodium lactate), different nitrogen sources (sodium nitrate, ammonium chloride and ammonium sulfate), different iron sources (ferrous carbonate, ferrous sulfate, ferric citrate, ferric quinate and compound iron), and different reducing agents (sodium thioglycolate, ascorbic acid and cysteine), and then placed in a shaker at 30°C and cultured at 110 r / min for 24 h, and the growth status (OD 565nm ) and magnetic generation capacity (C mag ). In order to determine the optimal formula of the required nutrients, three replicates were set for each treatment.

[0049] The results are as follows Figure 2 As shown, the best carbon source suitable for the growth and magnetization of magnetotactic bacteria MSR-1 strain is sodium lactate, the best nitrogen source is ammonium chloride, the best iron source is ferric citrate, and the best reducing agent is sodium thioglycolate.

[0050] 1.2 Optimization of single factor dosage of magnetotactic bacteria strain MSR-1 According to the results of “1.1 Optimization of single-factor conditions for magnetotactic bacteria MSR-1 strain”, the optimal formula was determined, and different carbon source concentrations (1, 2, 3, 4 and 5 g / L), different nitrogen source concentrations (0.1, 0.2, 0.3, 0.4 and 0.5 g / L), different iron source concentrations (0, 0.005, 0.010, 0.015 and 0.020 g / L) and different reducing agent concentrations (0.02, 0.03, 0.04, 0.05 and 0.06 g / L) were set respectively. The mixture was placed in a shaker at 30°C and cultured at 110 r / min for 24 h. The growth status (OD 565nm ) and magnetic generation capacity (C mag ). In order to determine the optimal range of the required nutrient addition, three replicates were set for each treatment. mag The value is obtained by adding a two-dimensional Helmholtz coil to the UV spectrophotometer to record the OD of the bacterial solution when the magnetic field is parallel to the light path and perpendicular to the light path. 565nm Values, respectively, are denoted as OD ∥ (OD parallel) and OD ⊥ (OD vertical), and calculate OD by ∥ With OD ⊥ The ratio of C mag .

[0051] The results are as follows Figure 2 As shown in the figure, the best carbon source for the growth and magnetism of magnetotactic bacteria MSR-1 strain is sodium lactate, with a dosage of 2-5 g / L. The best nitrogen source is ammonium chloride, with a dosage of 0.2-0.5 g / L. The best iron source is ferric citrate, with a dosage of 0.005-0.02 g / L. The best reducing agent is sodium thioglycolate, with a dosage of 0.03-0.06 g / L.

[0052] 1.3 Optimization of culture conditions of magnetotactic bacteria strain MSR-1 by response surface methodology The magnetotactic bacteria MSR-1 was used as the test strain. According to the results under "1.1" and "1.2", the carbon source addition amount, nitrogen source addition amount, iron source addition amount and reducing agent addition amount were used as four factors to evaluate the growth status (OD 565nm ) and magnetic generation capacity (C mag ) were used as two response values ​​to design a response surface experiment to optimize the optimal conditions for growth and magnetic production, and the reliability of the results was verified by repeated experiments.

[0053] The results are as follows Figure 3 , 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 and 14, the growth and magnetization capacity of magnetotactic bacteria MSR-1 were optimal when the addition amount of sodium lactate, ammonium chloride, ferric citrate and sodium thioglycolate were 3.38 g / L, 0.50 g / L, 0.011 g / L and 0.06 g / L respectively. The optimization results showed that under the best condition, OD 565nm 0.548, C mag The strain was cultured according to the theoretical value. In this case, the strain OD after repeated culture was 565nm Stable above 0.5, C mag It is stable above 1.3, which confirms the reliability of the experimental verification results of the addition amount of sodium lactate, ammonium chloride, ferric citrate and sodium thioglycolate.

[0054] 1.4 Cultivation time of magnetotactic bacteria strain MSR-1 The magnetotactic bacteria MSR-1 were taken out from the frozen glycerol stock and cultured for 0, 4, 8, 12, 16, 24, 30, 36 and 48 h, and the OD of the bacterial solution was measured. 565nm and C mag The wavelength of the UV spectrophotometer was adjusted to 565 nm, and the uninoculated culture medium was used as the blank to zero. 2.5 mL of the bacterial solution of the magnetotactic bacteria MSR-1 was injected into a quartz cuvette for measurement. Three replicates were set at each time point. The optimized growth curve of the magnetotactic bacteria MSR-1 and the dynamic synthesis process of magnetosomes were plotted using a UV spectrophotometer and a magnetic response instrument.

[0055] The results are as follows Fig.15 As shown in the figure, the strain growth curve shows that in the early stage of growth, the stagnation period of magnetotactic bacteria MSR-1 is short, indicating that the bacteria have good activity. After 8 hours of growth, the strain entered the logarithmic growth phase and reached the growth plateau after 24 hours. At this time, OD 565nm The value remained at around 0.5. When the culture time was extended to 48 h, OD 565nm The value decreased slightly to about 0.4. Regarding the synthesis dynamics of magnetosomes, the C mag The value shows a trend of decreasing first and then increasing. mag The value is relatively high, at 1.2. In the early stage of cultivation, C mag The value dropped from 1.2 to 0.6, which may be because MSR-1 began to grow at the beginning of growth, but had not yet synthesized a large number of magnetosomes. At 18 h of culture, the Cmag of MSR-1 quickly rose to 1.3 and remained relatively stable during the subsequent culture process, thus determining that the optimal culture time of the strain was 24 h.

[0056] Example 3 Cadmium removal effect and influencing factors of magnetotactic bacteria MSR-1 on cadmium-contaminated wastewater Cadmium chloride (CdCl2) solutions with different concentrations were used to simulate cadmium-contaminated industrial wastewater. Batch experiments were performed to study the effects of different solution pH values, initial Cd 2+ Effect of concentration, bacterial biomass and temperature on the removal of Cd from wastewater by magnetotactic bacteria MSR-1 2+ The specific settings are as follows: Set Initial Cd 2+ The concentration was 1 mg / L, the MSR-1 biomass concentration was 3.33 g / L and the temperature was 30℃. Experiments were conducted at different pH values ​​(3.0, 4.0, 5.0, 6.0, 7.0 and 8.0) to investigate the effect of pH. 2+ Experiments were conducted at 200 mg / L (0.5, 1, 2, 5, 10, 15 and 20 mg / L) to investigate the initial Cd 2+ The pH value was set to 6.0 and the initial Cd 2+ The concentration was 5 mg / L and the temperature was 30°C. Experiments were conducted at different MSR-1 biomass concentrations (1.67, 3.33, 6.67, and 10 g / L) to investigate the effect of bacterial biomass. 2+ The concentration was 5 mg / L and the MSR-1 biomass concentration was 3.33 g / L. Experiments were carried out in a shaker at different temperatures (20℃, 25℃, 30℃ and 37℃) to investigate the effect of temperature. 2+ The solution was added in a 50 mL centrifuge tube. Each inoculated experimental group was set up as a control group with an equal volume of 0.9% sterile NaCl solution, and each treatment was repeated three times. The Cd mass concentration was determined by inductively coupled plasma mass spectrometry (ICP-MS), and the pollution reduction and removal effect of magnetotactic bacteria on cadmium-contaminated water was studied under the optimal conditions.

[0057] The results are as follows Fig.16 As shown in the figure, the adsorption efficiency of Cd by magnetotactic bacteria MSR-1 is mainly affected by pH value, initial Cd concentration and bacterial biomass. Under the optimal reaction conditions of pH 8.0, temperature 30℃, adsorption time 1 h, and bacterial biomass 3.33 g / L, the adsorption efficiency of magnetotactic bacteria MSR-1 in a solution system with a Cd content of 1.0 mg / L can reach 87.8%.

[0058] Example 4 Effect of MSR-1 strain on Cd 2+ Adsorption thermodynamics and adsorption isotherms Set the solution pH to 6.0 and the initial Cd 2+ The concentration was 1 mg / L. 0.1 g of MSR-1 bacteria was added to 30 mL of Cd 2+ The solution was placed in a 100 mL Erlenmeyer flask (MSR-1 biomass concentration was 3.33 g / L), and a corresponding volume of 0.9% sterile NaCl solution was added as a control group. The Erlenmeyer flask was placed in a shaker at 180 r / min and 30°C, and samples were taken at 5, 10, 15, 30, 60, 120, 180 and 240 min after the reaction. The bacterial solution was centrifuged at 10,000 rpm for 3 min, and the supernatant was filtered through a 0.22 μm filter membrane and the cadmium mass concentration was determined using an inductively coupled plasma mass spectrometer (ICP-MS, PE Nexion 2000, USA). The kinetic model was fitted for the adsorption process, and the pseudo-first-order kinetic model (1) and pseudo-second-order kinetic model (2) used were as follows: (1) (2) Among them, q e is the theoretical adsorption amount at equilibrium (mg / g), t is the adsorption reaction time (min), q t is the adsorption amount at time t (mg / g), k1 is the pseudo-first-order adsorption rate constant (min -1 ), k2 is the pseudo-second-order adsorption rate constant (g / (mg·min)).

[0059] Experimental settings for adsorption isotherms: pH value was set at 6.0, MSR-1 biomass concentration was 3.33 g / L, and temperature was set at 30 °C. 2+ The experiments were carried out at different concentrations (0.5, 1, 2, 5, 10, 15 and 20 mg / L). The Langmuir isotherm adsorption model (3) and the Freundlich isotherm adsorption model (4) were used to fit the adsorption behavior of MSR-1 on Cd. 2+ Adsorption reaction: (3) (4) Among them, q e is the theoretical adsorption capacity at equilibrium (mg / g), C e Cd in solution at adsorption equilibrium 2+ Concentration (mg / L), q m is the monolayer saturated adsorption capacity (mg / g), k L is the Langmuir equilibrium constant, k F and n is the Freundlich constant.

[0060] The results are as follows Fig.17 As shown, MSR-1 has an effect on Cd 2+ The adsorption reaction of MSR-1 to Cd was rapid. 2+ The adsorption amount reached 94.3% of the equilibrium adsorption capacity and reached equilibrium 15 min after the reaction started.

[0061] MSR-1 to Cd 2+ The adsorption amount of Cd 2+ The increase in Cd concentration showed an obvious upward trend. 2+ When the concentration was 20 mg / L, the adsorption capacity of MSR-1 reached 1.20 mg / g.

[0062] Example 5 Cadmium removal effect of magnetotactic bacteria MSR-1 on cadmium-contaminated water Take simulated cadmium-containing industrial wastewater (using CdCl2 to prepare Cd-containing wastewater with different mass concentrations) 2+ Sewage, mass concentrations of 0.5, 1, and 2 mg / L respectively) were used as experimental samples for detection. The pH was adjusted to 6.0. Then, the activated magnetotactic bacteria MSR-1 was inoculated in the optimized culture medium in Example 2 for culture, placed in a shaker at 30°C, and cultured at 110 r / min for 24 h, and the expanded magnetotactic bacteria MSR-1 was added to the polluted water at an inoculum of 3.3 g / L. The groups of polluted water bodies mixed with the strain were stirred evenly, placed in a shaker at 30°C, and cultured at 180 r / min for 1 h before separating the sewage from the bacteria to achieve the removal of heavy metal cadmium in the sewage. The cadmium content of each group of water bodies after separation was detected, and 3 replicates were set for each group of treatments, and the cadmium mass concentration was determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0063] Results Fig.18 The results showed that the magnetotactic bacteria MSR-1 had a good adsorption capacity for cadmium in simulated cadmium-containing industrial wastewater of different mass concentrations. The adsorption efficiency of cadmium in simulated cadmium-containing industrial wastewater of different mass concentrations (mass concentrations were 0.5, 1, and 2 mg / L) was 92.2%, 87.2%, and 80.6%, respectively, showing a certain potential for cadmium removal, reduction, and remediation.

[0064] Example 6 Cadmium removal effect of magnetotactic bacteria MSR-1 on cadmium-contaminated soil Acidic soil (Changsha soil, total cadmium content 0.51 mg / kg, pH 5.28) and alkaline soil (Baiyin soil, total Cd content 1.01 mg / kg, pH 8.84) were taken as test soils, and magnetotactic bacteria MSR-1 was used as test strain. The above two test soils were ground to pass through a 0.85 mm nylon sieve, and a certain amount of test soil was weighed and added to a 50 mL centrifuge tube. Water was added at a soil-water mass ratio of 1: (8-12) and stirred evenly to obtain two groups of water-soil mixture samples. After the activated magnetotactic bacteria MSR-1 was expanded and cultured, 0.15 g of magnetotactic bacteria MSR-1 was resuspended in 1.0 mL NaCl (0.9%) solution and added to the above two groups of water-soil mixture samples as the experimental group. An equal volume of NaCl (0.9%) solution without bacteria was added as the control group. The centrifuge tube was placed in a shaker for oscillation reaction, then taken out and left to stand for 1 h. After a magnet was attached to the side wall of the centrifuge tube and left to stand for 24 h, the supernatant and soil were separated using a pipette without disturbing the magnetically enriched bacteria on the side wall, and the supernatant, the bacteria enriched by the magnet and the lower soil were saved respectively. The soil obtained after air-drying was digested and separated using a fully automatic graphite digestion instrument, and the obtained bacteria were digested using a graphite furnace digestion instrument. The above digestion solution and supernatant were filtered through a 0.45 μm filter membrane and then the cadmium content in the soil was determined using an inductively coupled plasma mass spectrometer (ICP-MS). Standard substances and blank samples were set for quality control.

[0065] The results are as follows Fig.19 As shown, the change in total cadmium in the soil after treatment and separation of magnetotactic bacteria MSR-1 indicated that after MSR-1 reacted with Changsha soil and Baiyin soil and was magnetically separated, the total Cd content of Changsha and Baiyin soils decreased by 12.7% and 15.6%, respectively, showing a certain potential for cadmium removal and reduction.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A strain of magnetotactic bacteria ( Magnetospirillum gryphiswaldense ) MSR-1 strain, characterized in that The deposit number of the magnetotactic bacteria MSR-1 strain is CCTCC NO: M 20242494.

2. A culture medium for culturing the magnetotactic bacteria MSR-1 strain according to claim 1, characterized in that: The carbon source in the culture medium includes one of sodium lactate, sodium acetate, tartaric acid and sodium lactate; the nitrogen source includes one of ammonium chloride, sodium nitrate and ammonium sulfate; the iron source includes one or more of ferrous sulfate, ferric citrate and ferric quinate; and the reducing agent includes one of sodium thioglycolate, ascorbic acid and cysteine.

3. The culture medium according to claim 2, characterized in that The amount of carbon source added to the culture medium is 2-5 g / L, the amount of nitrogen source added is 0.2-0.5 g / L, the amount of iron source added is 0.005-0.02 g / L, and the amount of reducing agent added is 0.03-0.06 g / L.

4. The culture medium according to claim 2, characterized in that The culture medium comprises 3-4 g / L sodium lactate, 0.35-0.50 g / L ammonium chloride, 0.010-0.015 g / L ferric citrate and 0.045-0.060 g / L sodium thioglycolate.

5. A method for culturing the magnetotactic bacteria MSR-1 strain according to claim 1, characterized in that: The method comprises the following steps: inoculating the activated magnetotactic bacteria MSR-1 into the culture medium according to claim 4, and culturing for 18 to 48 hours at 25 to 35° C. and 90 to 120 r / min.

6. The method for culturing the magnetotactic bacteria MSR-1 strain according to claim 5, characterized in that: The culture time is 20 h to 36 h.

7. A preparation product, characterized in that: The preparation product comprises the magnetotactic bacteria MSR-1 strain according to claim 1.

8. Use of the magnetotactic bacteria MSR-1 strain according to claim 1 or the preparation product according to claim 7 in repairing cadmium pollution, characterized in that: This includes remediation of cadmium contamination in water and / or remediation of cadmium contamination in soil.

9. The use according to claim 8, characterized in that: During the remediation, the pH of the water body or the soil is adjusted to 5.0-8.0, and the initial cadmium concentration is 2 mg / L or less.

10. The use according to claim 8, characterized in that: The inoculation amount of the magnetotactic bacteria MSR-1 in the water body is 3 to 10 g / L; The repaired soil is mixed with water to prepare a water-soil mixture, and the magnetotactic bacteria MSR-1 is inoculated into the water-soil mixture at an inoculation amount of 3% to 5% of the soil mass.

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