CN114774308A

CN114774308A - Application of combination of PQS and enterobacter hopcalis in inhibiting growth and reproduction of algae

Info

Publication number: CN114774308A
Application number: CN202210345570.9A
Authority: CN
Inventors: 杨美琦; 张斌; 吕烈阳; 何维; 谢文嘉; 刘伟
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2022-04-02
Filing date: 2022-04-02
Publication date: 2022-07-22
Anticipated expiration: 2042-04-02
Also published as: CN114774308B

Abstract

The invention discloses application of a combination of PQS and Enterobacter hollisae in inhibiting growth and propagation of algae. The algicidal agent comprises enterobacter heumakii and PQS, wherein the enterobacter heumakii is enterobacter heumakii F2. The PQS in the algicidal microbial inoculum does not have the functions of dissolving and inhibiting algae, the algae inhibiting effect of the Enterobacter hopcalis F2 can be improved through the synergistic cooperation of the PQS and the Enterobacter hopcalis F2, the algae inhibiting rate is as high as 83.81%, in addition, the addition of the PQS can remarkably reduce the chlorophyll a content in the algae liquid while not influencing the biomass of the Enterobacter hopcalis F2, the activity of ROS in the algae liquid can be remarkably improved, so that the flooding of water bloom can be effectively controlled, and the PQS has a larger application prospect in the eutrophication control of water bodies.

Description

Application of combination of PQS and enterobacter hopcalis in inhibiting growth and reproduction of algae

Technical Field

The invention belongs to the technical field of microorganisms, and particularly relates to application of a combination of PQS and enterobacter hopcalis in inhibition of growth and propagation of algae.

Background

In recent years, because wastewater and sewage contain a large amount of elements such as nitrogen and phosphorus, harmful algae such as microalgae, blue-green algae, green algae and diatoms in water bodies grow, and the harmful algae can gradually lose the self-cleaning capability of the water bodies, destroy natural landscapes, cause the death of aquatic animals and even harm the health of human beings. Therefore, the treatment of algae is a major problem in the treatment of water pollution.

Common methods for controlling algae are physical, chemical and biological methods. The physical method is mainly to remove algae by methods such as mechanical screening, forced interception, filtration and the like, and commonly adopts methods such as a micro-filter, activated carbon adsorption, ultrasonic waves and the like. But has the disadvantages of large investment and energy consumption and difficult fundamental solution of the problem of algae regeneration. The chemical method comprises adding algaecide (chemical oxidant, chemical salt) to remove algae, wherein the common algaecide comprises Al₂(SO₄)₃、CuSO₄、AgNO₃、AgBiO₃、NaBiO₃、H₂O₂、KMnO₄、ClO₂And the chemical algae removal has the advantages of simple operation method and obvious effect, but secondary pollution exists in the chemical algae removal. The biological method mainly adopts microbe prevention and treatment, terrestrial or aquatic plant inhibition and the like, and mainly utilizes competition of various biological preparations on nutrition, moisture and light in the environment or release of chemical substances to inhibit the growth of algae. Has the advantages of low cost, no pollution, easy degradation and environmental protection. However, the species of the algicidal bacteria available in the existing biological algae removal is single, so the algae lysing effect of the algicidal bacteria is limited, and the application of the biological algae removal is further limited.

Therefore, the development of a method capable of improving the algae treatment capacity of the algae-lysing bacteria has important significance for water body pollution treatment and ecological environment protection.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides the application of the combination of PQS and enterobacter hopcalis in inhibiting the growth and propagation of algae, the 3, 4-dihydroxy-2-heptyl-quinolone (PQS) in the algicidal agent does not have the functions of algae lysing and inhibiting algae, the algae inhibiting effect of the enterobacter hopcalis F2 can be improved through the synergistic cooperation of the PQS and the enterobacter hopcalis F2, and the algae inhibiting rate is as high as 83.81%; in addition, the addition of PQS can obviously reduce the chlorophyll a content in the algae liquid while not influencing the biomass of the Enterobacter hopcalis F2, and can obviously improve the activity of Reactive Oxygen Species (ROS) in the algae liquid, thereby effectively controlling the flooding of the algal bloom and having a larger application prospect in the treatment of water eutrophication.

In a first aspect of the invention, an algicidal agent is provided, wherein the algicidal agent comprises enterobacter hopcalis and PQS.

According to an aspect of the first aspect of the invention, in some embodiments of the invention, the enterobacter holdersonii is enterobacter holdersonii F2.

In some preferred embodiments of the invention, the Enterobacter huoshanense F2 has an NCBI ID of 5476961 and a GenBank sequence accession number of CP047570.1, for more detailed information see https:// www.ncbi.nl.nih.gov/assembly/GCF _ 009905155.1/.

In some preferred embodiments of the invention, the final concentration of PQS in the algicidal agent is 2-200. mu. mol/L.

In some more preferred embodiments of the present invention, the final concentration of PQS in the algicidal agent is 4 to 100. mu. mol/L.

In some more preferred embodiments of the invention, the final concentration of PQS in the algicidal agent is between 6 and 50. mu. mol/L.

In some more preferred embodiments of the present invention, the final concentration of PQS in the algicidal agent is 8 to 30. mu. mol/L.

In some preferred embodiments of the invention, the algae comprises microcystis aeruginosa.

Of course, the skilled person can use the algicidal agent to kill other water bloom algae according to actual use requirements, and the algicidal agent is not limited to microcystis aeruginosa.

The second aspect of the invention provides a method for preparing the algicidal agent, which comprises the following steps: mixing Enterobacter holtzeri and PQS.

According to the second aspect of the invention, in some embodiments of the invention, the effective viable count of the enterobacter hopcalis is 1 × 10⁸～1×10¹¹CFU/g。

In some preferred embodiments of the present invention, the effective viable count of said enterobacter hopcalis is 1 × 10⁹～1×10¹⁰CFU/g。

In some preferred embodiments of the present invention, the final concentration of PQS in the algicidal agent is 2 to 200. mu. mol/L.

In some more preferred embodiments of the present invention, the final concentration of PQS in the algicidal agent is 6 to 50. mu. mol/L.

In some more preferred embodiments of the invention, the enterobacter hopcalis is enterobacter hopcalis F2.

In some preferred embodiments of the present invention, the Enterobacter huwensis F2 is cultured in a broth (LB medium).

In some preferred embodiments of the present invention, the LB medium comprises 5-15 g/L peptone, 2-8 g/L beef extract, 0.5-2 g/L glucose and 0.5-2 g/L sodium chloride.

In some more preferred embodiments of the present invention, the LB medium comprises 10g/L peptone, 5g/L beef extract, 1g/L glucose and 1g/L sodium chloride.

In some more preferred embodiments of the present invention, the specific culturing steps of enterobacter hewinogradskyi F2 are: adding the formula into 1L of ultrapure water, adjusting the pH value to 7.2, carrying out autoclaving on the obtained culture medium at 121 ℃ for 30min, cooling the culture medium to room temperature, inoculating an Enterobacter hopcalis F2 strain with an inoculating loop, and placing the strain in a shaker at 37 ℃ and 150r/min for shake culture.

In a third aspect of the invention, there is provided a use of the algicidal agent of the first aspect of the invention for inhibiting the growth of algae.

According to a third aspect of the invention, in some embodiments of the invention, the algae comprises microcystis aeruginosa.

In some preferred embodiments of the present invention, the specific steps of the application are: the algicidal agent of the first aspect of the invention is added to an algae solution and cultured at 25-35 ℃.

In some more preferred embodiments of the present invention, the volume ratio of the algicidal agent to the algal solution is 1: (30-100).

In some more preferred embodiments of the present invention, the volume ratio of the algicidal agent to the algal solution is 1: (50-60).

In a fourth aspect of the invention, there is provided a use of the algicidal agent of the first aspect of the invention in water environmental treatment.

The beneficial effects of the invention are:

the PQS in the algicidal agent does not have the functions of algae solubilization and algae inhibition, the algae inhibition effect of the enterobacter hopcalis F2 can be improved through the synergistic cooperation of the PQS and the enterobacter hopcalis F2, the algae inhibition rate is as high as 83.81%, in addition, the addition of the PQS can obviously reduce the content of chlorophyll a in algae liquid while the biomass of the enterobacter hopcalis F2 is not influenced, the activity of ROS in the algae liquid can be obviously improved, so that the flooding of water bloom can be effectively controlled, and the PQS has a wide application prospect in water eutrophication control.

Drawings

FIG. 1 is a graph showing the growth curves of Enterobacter huwense F2 in the algal solutions of example 6 and comparative example 2 of the present invention.

Detailed Description

The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. These examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.

Culture of Enterobacter hollisae F2

The alga-inhibiting bacteria used in the embodiment of the invention are Enterobacter hopcalis F2, the NCBI ID of the Enterobacter hopcalis F2 is 5476961, the GenBank sequence number is CP047570.1, and the specific information can be seen in https:// www.ncbi.nl.nih.gov/assembly/GCF _ 009905155.1/. The culture was carried out using LB medium, the formulation of which is shown in Table 1.

TABLE 1 formulation of LB Medium

The specific culture steps are as follows: dissolving peptone, beef extract, glucose and sodium chloride in ultrapure water, metering the volume to 1L, adjusting the pH to 7.2 by using NaOH (the concentration is 3mol/L) or HCl (the concentration is 1mol/L), carrying out high-pressure sterilization on the obtained culture medium at 121 ℃ for 30min, cooling the culture medium to room temperature, inoculating an enterobacter hopcalis F2 strain by using an inoculating loop, and placing the strain in a shaking table at 37 ℃ and 150r/min for shake culture.

Wherein the effective viable count of Enterobacter hollisae F2 is 1 × 10⁹CFU/g。

Culture of Microcystis aeruginosa

The algae used in the embodiment of the invention is Microcystis aeruginosa FACHB 315, which is purchased from freshwater algae bank of Chinese academy of sciences. The culture medium used for activating and culturing the microcystis aeruginosa is BG11 culture medium.

The formula of BG11 culture medium is shown in Table 2.

TABLE 2 recipe and dosage of BG11 culture medium

Formulation(s)	Amount of the composition	Formulation(s)	Dosage of
				NaNO₃	1.5g	EDTA	0.001g
MgSO₄·7H₂O	0.075g	Ferric ammonium	0.006g
				Na₂CO₃	0.02g	CaCl₂·2H₂O	0.036g
K₂HPO₄	0.04g	Citric acid	0.006g
				Na₂SiO₃·9H₂O	0.058g	Distilled water	999mL
A5+Co solution	1mL	-	-

The formulation of A5+ Co solution is shown in Table 3.

TABLE 3 formulation ingredients and amounts of A5+ Co solution

Formulation(s)	Dosage of	Formulation(s)	Dosage of
				Co(NO₃)₂·6H₂O	0.05g	Na₂MoO₄·2H₂O	0.39g
ZnSO₄·7H₂O	0.22g	MnCl₂·4H₂O	1.86g
				H³BO³	2.86g	CuSO₄·5H₂O	0.08g
Distilled water	1000mL	-	-

Adjusting pH to 7.1 with NaOH or HCl after the preparation of the culture medium, sterilizing for 30min with high-pressure steam at 121 deg.C, cooling the culture medium, inoculating Microcystis aeruginosa, and culturing in a constant-temperature incubator under the following conditions: at 25 ℃, the illumination intensity is 2500lux, and the light-dark ratio is 15 h: and 9 h.

Example 1

The algicidal agent of example 1 was prepared by mixing 2mL of the bacterial solution of Enterobacter hopcalis F2 with PQS, wherein the final concentration of PQS was 2. mu. mol/L, and the effective viable count of Enterobacter hopcalis F2 was 1X 10⁹CFU/g。

Example 2

The algicidal agent of example 2 was prepared by mixing 2mL of the bacterial solution of Enterobacter hopcalis F2 with PQS, wherein the final concentration of PQS was 10. mu. mol/L, and the effective viable count of Enterobacter hopcalis F2 was 1X 10⁹CFU/g。

Example 3

The algicidal agent of example 3 was prepared by mixing 2mL of a bacterial solution of Enterobacter Huoshanense F2 and PQS, wherein the final concentration of PQS was 20. mu. mol/L, and the effective viable count of Enterobacter Huoshanense F2 was 1X 10⁹CFU/g。

Example 4

The algicidal agent in example 4 was prepared by mixing 2mL of the bacterial solution of Enterobacter hopcalis F2 and PQSWherein the final concentration of PQS is 200. mu. mol/L, and the effective viable count of Enterobacter hollyii F2 is 1X 10⁹CFU/g。

Detection of algae inhibiting effect of algicidal agent

Example 5

2mL of the algicidal agent of example 1 and 100mL of microcystis aeruginosa solution were added to a conical flask. The Erlenmeyer flask was placed in an incubator at 25 ℃ and incubated under light (illumination intensity 2500lux, light-dark ratio 15 h: 9h) for 7 days.

Example 6

2mL of the algicidal agent of example 2 and 100mL of microcystis aeruginosa solution were added to a conical flask. The Erlenmeyer flask was placed in an incubator at 25 ℃ and incubated under light (illumination intensity 2500lux, light-dark ratio 15 h: 9h) for 7 days.

Example 7

2mL of the algicidal agent of example 3 and 100mL of microcystis aeruginosa solution were added to a conical flask. The Erlenmeyer flask was placed in an incubator at 25 ℃ and incubated under light (illumination intensity 2500lux, light-dark ratio 15 h: 9h) for 7 days.

Example 8

2mL of the algicidal agent of example 4 and 100mL of Microcystis aeruginosa solution were added to the flask. The Erlenmeyer flask was placed in an incubator at 25 ℃ and incubated under light (illumination intensity 2500lux, light-dark ratio 15 h: 9h) for 7 days.

Comparative example 1

2mL of distilled water and PQS (final concentration of 10. mu. mol/L) were added to the flask together with 100mL of Microcystis aeruginosa algae solution as an algae-lysing substance. The Erlenmeyer flask was placed in an incubator at 25 ℃ and incubated under light (illumination intensity 2500lux, light-dark ratio 15 h: 9h) for 7 days.

Comparative example 2

2mL of enterobacter hopcalis F2 bacterial solution is used as an algae-lysing substance, and 100mL of microcystis aeruginosa algae solution is added into a conical flask. The Erlenmeyer flask was placed in an incubator at 25 ℃ and incubated under light (illumination intensity 2500lux, light-dark ratio 15 h: 9h) for 7 days.

Meanwhile, a blank control group is set, namely 2mL of distilled water and 100mL of microcystis aeruginosa solution are added into a conical flask. The Erlenmeyer flask was placed in an incubator at 25 ℃ and incubated under light (illumination intensity 2500lux, light-dark ratio 15 h: 9h) for 7 days.

Judgment Standard of algal inhibitory Effect

The algae inhibiting effect of the algicidal agent in examples 1 to 4 is determined according to the number of microcystis aeruginosa cells, the chlorophyll a content and the ROS activity detected in the algae liquid in examples 5 to 8.

First, count of the number of microcystis aeruginosa cells

The counting of the cell number of the microcystis aeruginosa is to directly count by adopting a blood counting chamber under an optical microscope, and of course, other conventional methods in the field can also be adopted for measuring. The calculation formula of the number of the microcystis aeruginosa cells is as follows:

the number of microcystis aeruginosa cells (one/mL) is N multiplied by 5 multiplied by the dilution multiple multiplied by 10⁴。

Wherein N is the number of algal cells directly obtained under the light microscope.

Secondly, content test of chlorophyll a

On the 4 th and 7 th days of the culture, 5mL of each of the algal solutions obtained from the Erlenmeyer flasks of examples 5 to 8 was sampled as a sample to be tested, and the content of chlorophyll a in the sample to be tested was measured.

The content of chlorophyll a in the algae can reflect the biomass of the algae in the water body and the change condition of the biomass of the algae, and is an important characteristic of the biomass of the algae. Normally growing algae have a high chlorophyll a content, and dead algae have a low chlorophyll a content, so that the chlorophyll a content in algae is used as an important index for measuring the survival of algae.

The content of chlorophyll a is measured by acetone extraction. The method comprises the following specific steps: performing suction filtration on 5mL of the algae solution obtained in the embodiments 5-8, putting a suction-filtered sample and about 0.15g of basic magnesium carbonate into a mortar at the same time, adding 2-3mL of acetone for grinding, grinding for 10-30s, centrifuging for 10min at 4000r/min, sucking a supernatant, fixing the volume to 10mL, and respectively measuring the absorbance A of the obtained supernatant at wavelengths of 630nm, 645nm, 663nm and 750 nm.

Wherein, the calculation formula of the chlorophyll a content is as follows:

wherein V is the volume (mL) of the algae liquid before suction filtration, namely 5 mL; a is absorbance; v₁The volume (mL) of the supernatant after constant volume is 10 mL; delta is the cell optical path (cm).

Third, determination of ROS Activity

The ROS is measured by adopting a ROS measuring kit of Nanjing institute of bioengineering. Respectively taking 5mL of the algae solution cultured on the 4 th day and the 7 th day in the embodiments 5-8, preparing single cell suspension of a sample to be detected, adding a 2, 7-dichlorofluorescein diacetate (DCFH-DA) fluorescent probe diluted in advance and having a working concentration of 10 mu mol/L to resuspend cell precipitates, incubating at 37 ℃ for 60min, collecting suspension with a probe mark, centrifuging at 1000r/min for 10min, discarding supernatant, collecting the cell precipitates, washing with Phosphate Buffer Solution (PBS) for 1-2 times, centrifuging again, and collecting the cell precipitates. After cell precipitation is resuspended by PBS buffer solution, 200 mu L of the cell precipitation is absorbed into a 96-well plate, and detection is carried out by a microplate reader, wherein the optimal excitation wavelength is 500nm (the range can be 500 +/-15 nm), the optimal emission wavelength is 525nm (the range can be 530 +/-20 nm), and the measurement result of ROS is expressed by a fluorescence value.

Statistics of results of algae inhibition

Table 4 shows the statistics of the number of microcystis aeruginosa cells, the content of chlorophyll a and the activity of ROS detected in the algae liquid of the blank control group, examples 5-8 and comparative examples 1-2.

TABLE 4 cell count, chlorophyll a content, and ROS activity of Microcystis aeruginosa detected in algae solutions of blank control, examples 5 to 8, and comparative examples 1 to 2

As can be seen from table 4, the number of microcystis aeruginosa cells in the algae solution treated by the algicidal agent in the embodiments of the invention in examples 5 to 8 is greatly reduced compared to the blank control group, wherein on the 4 th day of treatment, the number of microcystis aeruginosa cells in the algae solution in example 6 is the least, about 37% of the blank control group; on the 7 th day of treatment, the number of microcystis aeruginosa cells in the algae solution of the blank control group showed a slight increase trend, while the number of microcystis aeruginosa cells in the algae solution of the invention of examples 5-8 was continuously decreased, and also the decrease range of the number of microcystis aeruginosa cells in the algae solution of example 6 was the largest, and the number of microcystis aeruginosa cells in the algae solution of example 6 after the 7 th day of culture was about 50% of that after the 4 th day of culture. No significant change was observed in the microcystis aeruginosa cell count in the algal fluid of comparative example 1 compared to the blank control on either day 4 or day 7 of treatment, indicating that PQS alone had no inhibitory effect on the microcystis aeruginosa cell count in the algal fluid. The cell count of the microcystis aeruginosa in the algae liquid of the comparative example 2 is in a descending trend compared with that of a blank control group, but on the 4 th day of treatment, the cell count of the microcystis aeruginosa in the algae liquid of the comparative example 2 is higher than that of the microcystis aeruginosa in the invention examples 5-8, especially on the 7 th day of treatment, compared with the result on the 4 th day of treatment, the cell count of the microcystis aeruginosa in the algae liquid of the comparative example 2 is not changed basically, which shows that the enterobacter hopcalifornica F2 bacterial liquid has a weak inhibition effect on the cell count of the microcystis aeruginosa in the 4 th to 7 th days.

Comparing the content of chlorophyll a, it can be seen from table 4 that, compared with the blank control group, the content of chlorophyll a in the algae liquid treated by the algicidal agent of the embodiment of the present invention in examples 5 to 8 is greatly reduced, wherein, on the 4 th day of treatment, the content of chlorophyll a in the algae liquid of example 6 is the lowest, which is about 42% of that of the blank control group; on the 7 th day of the treatment, the content of chlorophyll a in the algal solution of the blank control group showed a slightly increasing trend, while the content of chlorophyll a in the algal solution of the invention in examples 5-8 was continuously decreased with the increase of the culture time, and the decrease of the content of chlorophyll a in the algal solution of example 6 was also the largest, and the content of chlorophyll a in example 6 after the 7 th day of the culture was about 50% of that after the 4 th day of the culture. The content of chlorophyll a in comparative example 1 was decreased, but the decrease was small, especially the content of chlorophyll a in comparative example 1 showed a tendency to increase as the incubation time increased, compared to the blank control, which also indicates that pure PQS had no inhibitory effect on the content of chlorophyll a in the algal solution. The content of chlorophyll a in comparative example 2 was reduced compared to the blank control group, but the content of chlorophyll a in comparative example 2 was reduced to a smaller extent compared to inventive examples 5-8.

The large accumulation of ROS in the algae cells can cause the damage of cell membranes of the algae cells and inhibit photosynthesis, so the large accumulation of ROS can inhibit the growth of the algae cells in the algae liquid. Regarding ROS activity, on the 4 th day of culture, compared with the blank control group, the ROS activity in the algae solution of the embodiments 5 to 8 of the present invention is greatly increased, especially in the embodiment 6, after the treatment with the algicidal agent of the embodiment 2 of the present invention, the ROS activity is increased to about 3 times of that of the blank control group, and the ROS activity in the algae solution of the blank control group shows a decreasing trend along with the increase of the culture time, whereas in the embodiments 5 to 8 of the present invention, the ROS activity continuously increases along with the increase of the culture time. In comparative example 1, ROS activity was substantially the same as that of the blank control, and the ROS activity of the algal solution of comparative example 1 showed a tendency to decrease with increasing culture time, again indicating that PQS alone had no inhibitory effect on algal cells. In comparative example 2, although the ROS activity in the algae liquid was increased compared to the blank control, the ROS activity in comparative example 2 was also not as high as the ROS activity in the algae liquid of examples 5-8 of the present invention.

In conclusion, it can be concluded that PQS alone cannot inhibit the growth of Microcystis aeruginosa, but the addition of PQS can improve the algae-inhibiting effect of Enterobacter holtzii F2, and the addition of PQS can prolong the time of the Enterobacter holtzii F2 for exerting the algae-inhibiting effect. In addition, the alga inhibiting rate of the algicidal agent in the embodiment of the invention can reach 83.81% at most.

Drawing of growth curve of Enterobacter hollisae F2

3mL of the algal solutions of example 6 and comparative example 2 were taken into a cuvette, and the absorbance at 600nm of each group of algal solutions was measured, respectively, and a growth curve of Enterobacter huoshimi F2 was plotted.

Fig. 1 is a growth curve of enterobacter holtziae F2 in example 6 and comparative example 2, and it can be seen from fig. 1 that no significant change is caused in the growth of enterobacter holtziae F2 itself after addition of PQS, and no biomass sudden increase occurs in the logarithmic growth phase of enterobacter holtziae F2, so the results in fig. 1 indicate that PQS does not promote algae inhibition by regulating the biomass change of enterobacter holtziae F2, and the possible reason is that the process of inhibiting algae by enterobacter holtziae F2 is regulated by PQS to promote the effect of inhibiting algae. Further carrying out gene sequencing on the Enterobacter hollisae F2, finding that the relative expression of the genes related to PQS is in a trend of increasing after the algae-lysing process occurs, and further explaining that PQS can achieve the effect of promoting the algae inhibition of the Enterobacter hollisae F2 by regulating the algae inhibition process of the Enterobacter hollisae F2.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. An algicidal agent is characterized by comprising enterobacter hopcalis and 3, 4-dihydroxy-2-heptyl-quinolone.

2. The algicidal agent according to claim 1, wherein the enterobacter hophallus is enterobacter hophallus F2.

3. The algicidal agent according to claim 1, wherein the final concentration of 3, 4-dihydroxy-2-heptyl-quinolone in the algicidal agent is 2 μmol/L to 200 μmol/L.

4. The method for preparing algicidal agent according to claim 1, comprising the steps of: mixing Enterobacter holtzeri with 3, 4-dihydroxy-2-heptyl-quinolone.

5. The method of claim 4, wherein the effective viable count of said Enterobacter holtzeri is 1 x 10⁸～1×10¹¹CFU/g。

6. The method of claim 4, wherein the final concentration of 3, 4-dihydroxy-2-heptyl-quinolone in the algicidal agent is 2 μmol/L to 200 μmol/L.

7. Use of an algicidal agent according to any one of claims 1 to 3 to inhibit the growth of algae.

8. The application of claim 7, wherein the application comprises the following specific steps: adding the algicidal agent according to any one of claims 1 to 3 to an algal solution, and culturing at 25 to 35 ℃.

9. The use of claim 7, wherein the volume ratio of the algicidal agent to the algae solution is 1: (30-100).

10. Use of an algicidal agent according to any one of claims 1 to 3 in water environmental treatment.