CN107964516B

CN107964516B - Acinetobacter and application thereof in degrading quorum sensing signal molecule DSF

Info

Publication number: CN107964516B
Application number: CN201711116059.7A
Authority: CN
Inventors: 陈少华; 叶田; 张炼辉; 范兴辉; 王惠杉; 阳芳; 冯芷萱; 单雯艳
Original assignee: South China Agricultural University
Current assignee: South China Agricultural University
Priority date: 2017-11-13
Filing date: 2017-11-13
Publication date: 2021-03-12
Anticipated expiration: 2037-11-13
Also published as: CN107964516A

Abstract

The invention discloses acinetobacter and application thereof in degrading quorum sensing signal molecules DSF. The invention provides a strain of acinetobacter (A)Acinetobacter lactucae) The strain QL-1 is preserved in the China center for type culture Collection in 2017, 9 and 11 months, and the preservation number is CCTCC NO: m2017487. The strain can grow by taking quorum sensing signal molecules DSF as a unique carbon source, can completely degrade 2mM DSF signal molecules within 15h, and has high degradation activity and stable degradation performance. The strain QL-1 has obvious biocontrol effect on black rot caused by Xanthomonas campestris XC1, has the characteristics of high growth speed, simple culture method, strong adaptability and difficult variation, has huge popularization and application potential in the prevention and treatment of pathogenic bacteria depending on DSF, can reduce the problem of pesticide abuse, and provides a new idea for biologically preventing and treating plant diseases.

Description

Acinetobacter and application thereof in degrading quorum sensing signal molecule DSF

Technical Field

The present invention belongs to the field of biological plant disease preventing and controlling technology. More particularly, it relates to Acinetobacter (Acinetobacter lactucae) and its application in degrading quorum sensing signal molecule DSF.

Background

Many microbial signaling molecules are sequentially discovered and isolated that regulate the expression of specific genes of a microbe, particularly various virulence factors, and coordinate population behavior, i.e., quorum sensing. DSF (differentiated Signal Factor) Signal molecules are unsaturated fatty acids derived from gram-negative pathogenic bacteria, and like quorum sensing systems which take AHLs as signals, the DSF Signal molecules also regulate and control important biological functions such as biofilm formation, cell growth, pathogenic Factor production and the like. It has been found that the DSF signaling molecule mediated quorum sensing is highly conserved among many plant pathogenic bacteria, including all bacteria of the genus Xanthomonas, Burkholderia, Pseudomonas aeruginosa, various marine bacteria, and the like. In addition to plant pathogenic bacteria, DSF signaling molecule mediated quorum sensing is also found in animal pathogens.

For example, Xanthomonas campestris (Xanthomonas campestris pv. campestris, Xcc) secretes DSF signal molecules, which generates quorum sensing phenomenon, resists against the immune defense system of plants, and infects plants to cause black rot. Black rot is an important agricultural disease, and particularly, is very destructive to brassica vegetables, resulting in reduced yield and quality. At present, the prevention and treatment measures for the pathogenic bacteria of the black rot disease at home and abroad are mainly chemical prevention and treatment, chemical pesticides such as bisquinuclein, bisultap, streptomycin sulfate, chloramphenicol and the like are widely applied, however, the use of a large amount of chemical pesticides already brings a series of well-known serious problems of environmental pollution, ecological balance damage, food safety and the like, and in addition, the overdose and overrange use of antibiotics enables more and more pathogenic bacteria to generate drug resistance, even multiple drug resistance. Therefore, the search for new and effective prevention strategies is urgent.

Quorum quenching is a new way for effectively preventing and treating plant bacterial diseases, namely, signal molecules of pathogenic bacteria are quenched to prevent the effective accumulation of the signal molecules, and when the concentration of the signal molecules is lower than a certain threshold value, the expression of pathogenic genes of the pathogenic bacteria cannot be activated, so that the communication among cells is damaged, and a quorum sensing system of the quorum sensing system is damaged. The microbial control strategy in the colony quenching method is to screen microbes from the environment to efficiently degrade colony induction signal molecules so as to achieve the control effect, has the advantages of simple and convenient operation, economy, practicality, environmental friendliness, high efficiency, short period and the like, and is the frontier and hotspot of the international plant disease control technical research.

At present, researches on quenching mechanisms of xanthomonas campestris DSF family quorum sensing signal molecules have been carried out at home and abroad, but the researches on the microbial degradation of the DSF are still rarely reported, and the screened DSF degradation strains have extremely small quantity and can not meet the requirements of biological control of diseases. Therefore, the method screens out microbial strains capable of efficiently degrading DSF quorum sensing signal molecules, researches the growth and degradation characteristics of the microbial strains, and has important practical significance for enriching microbial resources, solving the problems of abuse crisis of antibiotics and pesticide residue pollution and preventing and treating DSF mediated pathogenic bacteria.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects and shortcomings of the prior art, and provide Acinetobacter (Acinetobacter lactucae) with the capability of efficiently degrading quorum sensing DSF signal molecules, and application thereof in degradation of DSF signals and/or DSF signal analogues. The research of the invention discovers that the acinetobacter has obvious and rapid degradation effect on quorum sensing signal molecules DSF, and has huge application potential in the aspect of preventing and treating DSF-mediated pathogenic bacteria, so that a new development approach is provided for a treatment strategy which replaces chemical prevention with biological prevention and treatment and takes blocking quorum sensing as a target without causing selective pressure.

The invention aims to provide acinetobacter capable of efficiently degrading quorum sensing signal molecules DSF.

Another objective of the invention is to provide an application of acinetobacter in degrading quorum sensing signal molecule DSF.

The above purpose of the invention is realized by the following technical scheme:

the invention provides an Acinetobacter (Acinetobacter lactucae) strain QL-1 capable of degrading DSF signal molecules, which is preserved in China Center for Type Culture Collection (CCTCC) in 2017, 9 and 11 months, and the preservation number is CCTCC NO: m2017487.

The strain is obtained by artificial screening, separation and purification from rice root-surrounding soil collected from the test field of southern agricultural university of Guangzhou Hua, and the strain is identified as Acinetobacter (Acinetobacter lactucae) through morphological characteristics, physiological and biochemical characteristics and 16S rDNA phylogenetic analysis of the strain.

The colony morphology of the strain QL-1 is characterized in that: culturing on nutrient agar plate for 48h, the colony is flat, the surface is smooth and opaque, and the edge is neat; the cells were cultured in a nutrient broth for 48 hours to form a diffuse turbidity. The morphological characteristics of the thalli observed by an electron microscope are as follows: the thallus is rod-shaped or nearly spherical, and is in a pair or chain shape with different lengths.

The physiological and biochemical characteristics of the strain QL-1 are as follows: the growth medium is a gram-negative bacterium, is aerobic, has positive citrate utilization test and negative oxidase test, hemolytic test, gelatin liquefaction test and starch hydrolysis test, does not grow at the temperature of below 10 ℃, has the optimal growth temperature of 30 ℃ and the optimal growth pH value of 7.0. D-glucose, D-fucose, L-arginine, L-alanine, L-lactic acid, etc. can be used, and D-lactose, sucrose, glycerol, D-mannitol, etc. can not be used.

The resistance of the strain QL-1 to chloramphenicol reaches 200 mu g/mL or more, the resistance to ampicillin reaches 50 mu g/mL, the resistance to rifampicin and carbenicillin reaches 20 mu g/mL, and the resistance to streptomycin, kanamycin, gentamicin and tetracycline is less than 10 mu g/mL.

Experimental research shows that the acinetobacter strain QL-1 has obvious and rapid degradation effect on quorum sensing signal molecules DSF, can normally grow in a culture medium with DSF with the concentration as high as 5mM as a unique carbon source, can completely decompose quorum sensing DSF signal molecules with the initial concentration of 2mM within 15h, and has huge application potential in the aspect of preventing and treating DSF-mediated pathogenic bacteria harm.

Therefore, the use of acinetobacter in the degradation of quorum sensing signaling molecules DSF and/or DSF signal analogues, or in the preparation of products for degrading DSF and/or DSF signal analogues, should be within the scope of the present invention.

The DSF signal analogs include cis-2-dodecenoic acid, (2Z,3Z) -11-methyl-2, 5-diene-12-alkanoic acid.

The application of acinetobacter in the prevention and treatment of plant diseases mediated by DSF or the application in the preparation of prevention and treatment preparations of pathogenic bacteria depending on DSF also belong to the protection scope of the invention.

Preferably, in any of the above applications, the acinetobacter is acinetobacter strain QL-1.

The invention also provides a method for preventing and treating the disease of pathogenic bacteria depending on the DSF, which is to spray the plant by using the bacterial suspension of the acinetobacter strain QL-1 so as to prevent the infection of the pathogenic bacteria depending on the DSF.

Experiments show that the acinetobacter strain QL-1 has a significant biocontrol effect on diseases caused by pathogenic bacteria that depend on DSF, including Xanthomonas (Xanthomonas), Burkholderia (Burkholderia) or Pseudomonas aeruginosa (Pseudomonas aeruginosa), and therefore, in any of the above-mentioned applications, the pathogenic bacteria that depend on DSF include: xanthomonas (Xanthomonas), Burkholderia (Burkholderia) or Pseudomonas aeruginosa (Pseudomonas aeruginosa) and the like.

Preferably, when the method is applied, the optimum pH value of the acinetobacter for degrading the DSF is 6.8-7.2, and the optimum temperature is 28-30 ℃. The pH of the suspension of the acinetobacter strain QL-1 can be controlled to be 6.8-7.2, and crops can be sprayed at the ambient temperature of 28-30 ℃.

Preferably, when applied, the most suitable culture medium for preparing the acinetobacter bacterial suspension is MSM culture medium, and the formula is as follows: (NH4)₂SO₄，2.0g/L；CaCl₂·2H₂O，0.01g/L；Na₂HPO₄·12H₂O，1.5g/L；KH₂PO₄，1.5g/L；MgSO₄·7H₂O，0.2g/L；FeSO₄·7H₂O，0.001g/L，pH 7.2。

In addition, a degrading bacterial agent containing the strain QL-1 and/or the bacterial suspension thereof and capable of degrading the quorum sensing signal molecule DSF, and a biocontrol agent containing the strain QL-1 and/or the bacterial suspension thereof and capable of resisting pathogenic bacteria causing the disease depending on the DSF are also within the protection scope of the invention.

Particularly preferably, the degrading microbial inoculum and the biocontrol agent are prepared from a bacterial suspension obtained by fermenting the strain QL-1.

Experiments show that the fermentation supernatant of the strain and DSF are cultured together, and the DSF is not obviously degraded after extraction and liquid chromatography analysis, so that the DSF is not a fermentation product which has the degradation effect. Therefore, the bacterial suspension obtained by fermentation is used for preparing degradation bacteria and biocontrol agents.

The invention also provides a preparation method of the bacterial strain QL-1 bacterial suspension, which comprises the following steps: specifically, the strain QL-1 is streaked on an LB solid culture medium flat plate, the strain QL-1 is cultured for 12-36 h at the temperature of 28-30 ℃, a single colony is selected and inoculated in an LB liquid culture medium for pre-culture to a logarithmic phase, the obtained strain is washed and resuspended by 0.9% of sterile physiological saline to be used as a seed suspension, the seed suspension is inoculated in the LB liquid culture medium according to the inoculum size of 0.5-5% (preferably 1%) of the volume ratio to the logarithmic phase, and the strain is resuspended by PBS buffer solution to obtain the bacterial suspension of the strain QL-1. The concentration of the bacterial suspension is not strictly limited, and can be specifically adjusted according to the actual disease degree and the application effect.

Preferably, the formulation of the LB medium is: 10.0g/L of tryptone, 5.0g/L of yeast extract, 10.0g/L of sodium chloride, pH 6.8-7.2 and sterilization at 121 ℃ for 15-25 min. The LB solid medium formulation is to add 1.5% (w/v) agar to the liquid medium.

The invention has the following beneficial effects:

the invention provides an acinetobacter strain QL-1, which has high DSF degradation activity, wherein the high degradation activity means that quorum sensing DSF signal molecules with initial concentration of 2mM can be completely decomposed in MSM culture medium with DSF as a unique carbon source within 15 h.

Experiments show that the degrees of black rot diseases caused by radish fleshy root slices are obviously reduced when the acinetobacter QL-1 and the xanthomonas campestris XC1 are inoculated together compared with the single XC1 inoculation, so that the prevention and treatment effects on the radish black rot are achieved. In addition, the strain QL-1 is separated from the rice rhizosphere soil, and the strain QL-1 can be well adapted to the environment and is environment-friendly.

The acinetobacter has high degradation activity to quorum-sensing DSF signal molecules in plant pathogenic bacteria, stable degradation performance and environmental friendliness, so that the strain QL-1 has huge popularization and application potential in prevention and treatment of the plant pathogenic bacteria depending on DSF-mediated pathogenicity, and meanwhile, the problem of overuse of antibiotics and pesticide residue pollution can be reduced, and a new idea is provided for biological prevention and treatment of plant diseases.

Drawings

FIG. 1 is a colony morphology of the strain QL-1 of the present invention on nutrient agar medium.

FIG. 2 is a colony morphology of the strain QL-1 of the present invention on a blood plate medium.

FIG. 3 is a scanning electron micrograph of the strain QL-1 of the present invention.

FIG. 4 is a phylogenetic tree analysis diagram of the strain QL-1 of the present invention.

FIG. 5 is a graph showing the growth of strain QL-1 of the present invention in various antibiotics.

FIG. 6 is an HPLC chart showing the degradation of DSF by the strain QL-1 of the present invention (FIG. A is a chart showing the non-inoculated strain QL-1, and FIG. B, C, D, E is a High Performance Liquid Chromatography (HPLC) chart showing the degradation of 2mM DSF by the strain QL-1 for 6h, 9h, 12h and 15h, respectively).

FIG. 7 is a graph showing the growth curve and degradation curve of strain QL-1 of the present invention using DSF as a sole carbon source.

FIG. 8 shows the onset of the succulent root section of radish after the bacterial strain QL-1 of the present invention is inoculated alone and inoculated with Xanthomonas campestris for 48h together with the succulent root section of radish.

Detailed Description

The invention is further described with reference to the drawings and the following detailed description, which are not intended to limit the invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Unless otherwise indicated, reagents and materials used in the following examples are commercially available.

Example 1 acquisition and characterization of Acinetobacter strain QL-1

1. Isolation and screening of Strain QL-1

(1) Soil sample collection: rice rhizosphere soil collected from a test field is used as a microbial source.

The soil sample is collected from the rice root-surrounding soil of the experimental field of southern China agriculture university in Guangzhou, Guangdong at 2016, and the soil from the surface layer to the deep layer of 5cm is sampled, bagged and stored to be used as a microbial source for strain separation.

(2) Enrichment culture of the strain: MSM medium was prepared by filling 50mL of MSM medium into a 250mL Erlenmeyer flask and sterilizing, cooling, adding DSF mother liquor (methanol as solvent) under aseptic conditions to make the final mass concentration of DSF 50 μ M, adding 5g of soil sample, shake culturing at 30 deg.C and 200rpm for 7d, and transferring into a second batch of MSM medium with the final mass concentration of DSF 100 μ M in an amount of 10%. After culturing for 7d under the same conditions, transferring the cells into MSM culture medium with the final mass concentration of 200 μ M of DSF according to the inoculation amount of 10%, and continuing culturing for 7 d. And by analogy, the mass concentration of the DSF is continuously increased.

The formula of the MSM culture medium is as follows: k₂HPO₄，10.5g/L；KH₂PO₄，4.5g/L；(NH₄)₂SO₄，2.0g/L；MgSO₄·7H₂O，0.2g/L；FeSO₄，0.005g/L；CaCl₂，0.01g/L；MnCl₂，0.002g/L；pH 7.2。

(3) Strain separation and purification: and (5) performing separation and purification by adopting dilution and flat plate coating and scribing.

Taking 1mL of final MSM culture medium fermentation liquor, and gradually diluting the concentration of the final MSM culture medium fermentation liquor to 10 in a gradient manner by using sterile water^-1、10^-2、10^-3、10^-4、10^-5、10^-6、10^-7、10^-8Then 100 mul of diluted fermentation liquor with each concentration gradient is sucked and evenly coated on an LB solid plate, the culture is carried out at 30 ℃, single colonies with different colony forms are picked out, and the streaking culture and the purification are carried out on the LB solid plate repeatedly until single strains are separated. Storing the single strain at-80 deg.C, and screening when DSF degradation rate is determined by HPLC.

(4) Screening of strains: strains isolated from soil samples were screened using MSM basal medium with DSF as the sole carbon source.

Inoculating the single colony of the separated and purified strain into 50mL MSM basal medium with DSF as a unique carbon source to ensure that the final mass concentration of the DSF is 5mM, and performing DSF extraction and HPLC (high performance liquid chromatography) to measure the residual amount of the DSF after shaking culture at 30 ℃ and 200rpm for 48 h.

The extraction method of the DSF comprises the following steps: taking 5mL to 15mL centrifuge tubes for each sample, centrifuging for 5min at 4000rpm, taking supernatant, transferring the supernatant into a 50mL separating funnel, adding 5mL ethyl acetate into the separating funnel, shaking uniformly, violently shaking for 3min, standing, layering, discarding the lower layer solution into the 15mL centrifuge tubes, filtering the upper layer solution into a 50mL round-bottom flask through a funnel, and paving filter paper in the funnel. The lower solution was extracted 1 more time as described above. The filtrate was combined into a round-bottomed flask, concentrated at 50 ℃ at constant temperature and evaporated to dryness, the round-bottomed flask was washed with chromatographic methanol 2 times, the volume was adjusted to 2mL, the mixture was filtered through a 0.45. mu.M organic filter membrane into a sample bottle, and the residual amount was measured by HPLC.

Conditions for determining residual amount of DSF by HPLC: c₁₈And (3) a reverse chromatographic column, wherein the flow rate is 1mL/min, the column temperature is 35 ℃, and the mobile phase is methanol: 80 parts of water: 20 (v: v), the detection wavelength is 210nm, and the sample injection amount is 20 mu L.

The DSF degradation rate was calculated according to the following formula: percent degradation (%) - (1-A)₁/A₀)×100，A₁To degrade the residual concentration of DSF after bacterial treatment, A₀As a control for residual concentration of DSF after treatment.

Finally obtaining the strain with the highest DSF degradation rate, which is named as QL-1.

2. Identification and phylogenetic analysis of strain QL-1

(1) And (3) colony morphology characteristics: the strain QL-1 was streaked on LB solid medium and cultured at 30 ℃ for 48 hours. As shown in FIG. 1, the colonies were beige in color, flat, smooth and opaque, and had clean edges. The strain QL-1 is diffusively turbid and aerobic in LB liquid medium.

As shown in FIG. 2, bacterial colonies of the strain QL-1 on a blood plate are milky white, small, round and convex, smooth and translucent in surface and regular in edge.

(2) Morphological characteristics of the thallus: as shown in FIG. 3, the cells are rod-shaped or nearly spherical, have a size of (8.0 to 12.0) × (8.0 to 10.0) μm, and are paired or have chains of different lengths.

(3) Physiological and biochemical characteristics: the physiological and biochemical characteristics of the strain QL-1 are as follows: the bacillus subtilis is a gram-negative bacterium, is aerobic, has positive citrate utilization test and negative oxidase test, hemolytic test, gelatin liquefaction test and starch hydrolysis test, does not grow at the temperature of below 10 ℃, has the optimal growth temperature of 30 ℃ and has the optimal pH of 7.0. D-glucose, D-fucose, L-arginine, L-alanine, L-lactic acid, etc. can be used, and D-lactose, sucrose, glycerol, D-mannitol, etc. can not be used. The results of physiological and biochemical identification and the results of carbon source utilization are shown in tables 1 and 2, respectively.

TABLE 1 physiological and biochemical identification results of the strain QL-1

Note: -: negative or not utilized; +: positive or use

TABLE 2 carbon source utilization results of Strain QL-1

Note: "-" indicates a negative reaction or not utilized; "+" indicates a positive reaction or use

(4)16S rDNA sequence and phylogenetic analysis:

the 16S rDNA gene sequence of the strain QL-1 is obtained, the length is 1417bp, and then the strain QL-1 is compared with an NCBI database (http:// www.ncbi.nlm.nih.gov /), and the strain QL-1 and Acinetobacter sp.NRRL B-41902(GenBank accession number: KU921101.1) are found to have good homology, the similarity reaches 99 percent, and the phylogenetic tree thereof is shown in figure 4.

(5) Biolog automatic analysis system identification of microorganisms:

the strain QL-1 was further identified by a Biolog automated microbiological analysis System, and the strain QL-1 was cultured for 22 hours and then read on a Biolog Microstation System reader. The results of carbon source utilization are shown in Table 2.

In conclusion, the strain QL-1 is identified by morphological characteristics, physiological and biochemical characteristics, 16S rDNA gene sequence and Biolog microorganism automatic analysis system, the strain identification result is Acinetobacter (Acinetobacter lactucae), and the strain is preserved in China Center for Type Culture Collection (CCTCC) in 2017, 9 and 11 days, and the preservation number is CCTCC NO: m2017487, the preservation address is Wuhan university in China.

Example 2 antibiotic susceptibility analysis of Strain QL-1

In order to be able to better study the biocontrol potential of the strain QL-1 obtained in example 1, we studied the antibiotic susceptibility of this strain QL-1. As shown in FIG. 5, the strain showed resistance to Chloramphenicol (CM) of 200. mu.g/mL or more, Ampicillin (AMP) of 50. mu.g/mL, and Rifampicin (RIF) and Carbenicillin (CARB) of 20. mu.g/mL^-1The resistance to Streptomycin (STR), Kanamycin (KAN), Gentamicin (GEN) and tetracycline (TET) is less than 10 mu g/mL. This result is useful for reference in subsequent studies to select suitable antibiotics.

EXAMPLE 3 determination of DSF relationship curves for growth and degradation of Strain QL-1

1. Selecting a single bacterial colony of the strain QL-1, inoculating the single bacterial colony in an LB culture medium for pre-culture till logarithmic phase, centrifuging the obtained bacterial liquid at 4000rpm for 5min, discarding the supernatant, washing the thalli with 0.9% sterile physiological saline, resuspending the thalli to obtain a seed suspension, and then adding 1: 100 inoculum size was inoculated into 50mL MSM basal medium, and DSF stock solution was added to a final concentration of 2mM, cultured at 30 ℃ for 24h at 200rpm, and sampled periodically. Samples were taken at different time points and,measuring OD with spectrophotometer₆₀₀The values represent the growth of strain QL-1 and the residual DSF content by HPLC represents the degradation of strain QL-1 to DSF.

2. The HPLC detection results are shown in FIG. 6 (wherein, FIG. A is a control chart of the non-inoculated strain QL-1, FIG. B, C, D, E is a degradation chart of the strain QL-1 to DSF 6h, 9h, 12h, 15 h), the degradation rates of the strain QL-1 to DSF at 6h, 9h, 12h, 15h respectively reach 7.3%, 34.1%, 78.5% and 100%, and the growth curves and degradation curves of the corresponding strain QL-1 with DSF as the sole carbon source are shown in FIG. 7.

As can be seen from FIG. 7, the degradation of the DSF is positively correlated with the growth of the strain, the strain grows in a logarithmic phase without a retention period in the presence of the DSF, the strain rapidly enters a logarithmic phase of growth, 9-12 h is the logarithmic phase of the strain growth, the strain degrades the DSF most rapidly at the moment, the strain is cultured for 15h, and the DSF is completely decomposed. The natural degradation rate in 24h of DSF in the control was less than 20%.

The result shows that the acinetobacter QL-1 has obvious and rapid degradation effect on the DSF, and has great application potential in the aspect of preventing and treating the pathogenic bacteria harm mediated by the DSF.

EXAMPLE 4 Effect of QL-1 Strain on the prevention of radish Black rot

1. In this example, xanthomonas campestris was taken as an example to study the biocontrol effect of strain QL-1 on pathogenic bacteria dependent on DSF.

Respectively selecting single bacterial colonies of a strain QL-1 and a DSF-dependent pathogenic bacterium Xanthomonas campestris XC1, respectively inoculating the single bacterial colonies into an LB culture medium for pre-culture to a logarithmic phase, centrifuging the obtained bacterial liquid at 4000rpm for 5min, discarding supernatant, washing and re-suspending the bacterial bodies with 0.9% sterile physiological saline to obtain a seed suspension, and then mixing the bacterial suspensions with a mixture of 1: 100 inoculum size was inoculated into LB medium, cultured at 30 ℃ and 200rpm to log phase, and the cells were resuspended to OD with PBS buffer₆₀₀When the strain is 1.0, a bacterial suspension of the strain QL-1 and xanthomonas campestris XC1 is obtained.

And uniformly mixing the strain QL-1 bacterial suspension and Xanthomonas campestris XC1 bacterial suspension to obtain a mixed bacterial liquid. Cleaning succulent radix Raphani with distilled water, slicing after drying, transversely cutting to obtain 0.3cm thick disc, and adding into the discPetri dishes (filled with cotton that has been soaked with sterile water). Inoculating 100 μ L mixed bacterial liquid on radish fleshy root slice, and inoculating strain QL-1 and Xanthomonas campestris XC1 OD in the mixed bacterial liquid₆₀₀All are 0.2, the cells were spread evenly with a spreading bar, incubated at 30 ℃ for 48 hours, and the onset of disease was observed. The single inoculation strain xanthomonas campestris and the single inoculation strain QL-1 are respectively used as a positive control and a negative control.

2. The results are shown in FIG. 8, the extent of the black rot disease of radish is obviously reduced when the strain QL-1 and the Xanthomonas campestris XC1 are inoculated together compared with the single inoculation of XC 1. The experimental result shows that the strain QL-1 has obvious biocontrol effect on black rot caused by Xanthomonas campestris XC 1.

The embodiments mainly illustrate the strains and the application ideas based on the strains, and the simple parameter replacement in the embodiments can not be described in detail in the embodiments, but the invention is not limited thereby, and any other changes, modifications, substitutions, combinations and simplifications which do not depart from the spirit and principle of the invention should be regarded as equivalent replacement ways which are included in the scope of the invention.

Claims

1. An Acinetobacter (Acinetobacter lactucae) strain QL-1 capable of degrading quorum sensing signal molecules DSF is characterized in that the strain is preserved in China center for type culture Collection in 2017, 9 and 11 months, and the preservation number is CCTCC NO: m2017487.

2. Use of the acinetobacter strain QL-1 of claim 1 for degrading quorum sensing signal molecule DSF, or for preparing a product for degrading quorum sensing signal molecule DSF.

3. Use of the acinetobacter strain QL-1 according to claim 1 for the control of quorum sensing signaling molecule DSF-mediated pathogenic plant diseases, or for the preparation of control formulations for pathogenic bacteria that depend on quorum sensing signaling molecule DSF.

4. A method for controlling pathogenic diseases which are pathogenic depending on quorum sensing signal molecules DSF, characterized in that plants are treated with a suspension of acinetobacter strain QL-1 according to claim 1.

5. The method according to claim 4, wherein the pathogenic bacteria that are pathogenic depending on quorum sensing signaling molecule DSF are: xanthomonas (Xanthomonas), Burkholderia (Burkholderia) or Pseudomonas aeruginosa (Pseudomonas aeruginosa).

6. The method according to claim 4, wherein the pH optimum of the Acinetobacter bacterial suspension is 6.8-7.2, and the temperature optimum is 28-30 ℃ when the method is applied; when in use, the most suitable culture medium for preparing the acinetobacter bacterial suspension is an MSM culture medium, and the formula is as follows: (NH4)₂SO₄，2.0g/L；CaCl2·2H₂O，0.01g/L；Na₂HPO₄·12H₂O，1.5g/L；KH₂PO₄，1.5g/L；MgSO₄·7H₂O，0.2g/L；FeSO₄·7H₂O，0.001g/L，pH 7.2。

7. A method according to claim 4, wherein the treatment is by spraying the plant.

8. A degrading bacterial agent capable of degrading quorum sensing signal molecule DSF, which contains the strain QL-1 and/or bacterial suspension of the strain QL-1 of claim 1.

9. A biocontrol agent for pathogenic bacteria which depend on quorum sensing signaling molecules DSF for pathogenesis, comprising the strain QL-1 and/or its bacterial suspension according to claim 1.