Synthetic flora constructed by paracoccus and application thereof

Abstract

The invention discloses paracoccum C4-4 and C5-3, the preservation number of the paracoccum C4-4 and C5-3 is CGMCC (China General Microbiological Culture Collection Center) NO: 31971, the paracoccum C5-4 and C5-3 are classified and named as Paracoccus communis, and the preservation number of the paracoccum C4-4 and C5-3 is CGMCC NO: 31972, and the paracoccum C5-3 is classified and named as Paracoccus communis. Researches show that C4-4 and C5-3 both have strong ecological adaptability and good growth promoting ability, and can improve the environment in the soil by combining with organic materials. The synthetic flora constructed by using the paracoccus comprises the C4-4 and the C5-3. Tests prove that the synthetic flora has the advantages of C4-4 and C5-3, and the flora has higher alkali production and growth promotion capabilities; good ecological adaptability is achieved, the pH adaptation range is 4-8, and manganese stress resistance can reach 5000 micromoles per liter; the pH of the culture medium can be obviously improved, and the alkalization effect is obvious. The soil conditioner capable of improving acid soil and promoting plant growth is prepared by taking the synthetic flora as a microbial inoculum and compounding the microbial inoculum with an organic material. When the modifier is applied to acid and lean soil, the soil pH can be remarkably increased, the content of organic matters and nitrogen phosphorus and potassium in the soil is increased, and root growth is promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of soil improvement, and in particular relates to a synthetic bacterial community constructed with Paracoccus and applications thereof. Background Art

[0002] Acidic soil is one of the common problems in global agricultural production. How to effectively improve these soils and increase their fertility and productivity has become an urgent problem to be solved.

[0003] In order to improve acidic soil and increase its fertility and productivity, traditional methods mainly include lime neutralization, application of organic fertilizers and use of chemical amendments. Although these methods can increase soil pH and increase organic matter content to a certain extent, they have some limitations. Although lime neutralization can quickly increase soil pH, its effect is short-lived and can easily cause soil compaction and acid reversion. Although the application of organic fertilizers can help increase soil organic matter content and improve soil structure, it decomposes quickly, requires large application amounts and is costly. Although chemical amendments are effective, they pose environmental pollution and safety risks. In addition, these methods have limited effects on the restoration of soil biological network structure.

[0004] In recent years, the application of microbial technology in soil improvement has attracted widespread attention. Microorganisms can not only directly participate in the decomposition of soil organic matter and nutrient cycling, but also improve soil structure through metabolic activities and enhance the soil's ability to retain water and fertilizer. The Chinese patent application "Application of microbial composite agents in alleviating the harm of soil acidification to plants" (patent number 2023112456870, published on January 30, 2024) explains that the beneficial bacteria contained in microbial agents are not only widely applicable, but also can enhance the interaction ability of microorganisms in the soil, diversify the community in the soil, and thus greatly improve the soil. According to research, Paracoccus microorganisms can reduce nitrates and nitrites in the soil to nitrogen gas through nitrification and denitrification, reduce nitrogen loss, and increase soil pH (Zhu YG et al. Environmental Science, 2023, 2014, 1(2): 792-800). However, Paracoccus microorganisms are currently mostly used for denitrification of wastewater (Mo Baolan et al. Aquatic Science and Technology Information, 2024 / 5 / 28), and in soil, they are mainly focused on the degradation of organic matter such as polycyclic aromatic hydrocarbons (CHEN, W, et al. Pedosphere, 2022, 2(5): 673-685). There is a lack of research on microorganisms represented by Paracoccus in improving soil and promoting plant growth. Therefore, research on the application of Paracoccus in soil improvement is still in its initial stage, and a systematic technical solution and application model have not yet been formed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a synthetic bacterial community constructed with Paracoccus and its application to solve the problems of low pH and low organic matter in acidic and lean soil.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] Paracoccus communis C4-4 or C5-3, whose deposit number is CGMCC NO: 31971 and whose classification name is Paracoccus communis, or whose deposit number is CGMCC NO: 31972 and whose classification name is Paracoccus communis.

[0008] The 16S rRNA gene of the above-mentioned Paracoccus has the base sequence of SEQ.ID.NO.1 or SEQ.ID.NO.2 in the sequence listing.

[0009] The synthetic bacterial community constructed with Paracoccus includes the above-mentioned two strains of Paracoccus C4-4 and C5-3.

[0010] Application of the above-mentioned Paracoccus or synthetic bacterial flora in soil improvement or plant growth promotion.

[0011] The soil is acidic and lean soil, and the invention can improve soil pH, organic matter, effective NPK, and promote plant growth; the plant is lettuce, and the invention can improve the plant's growth-promoting ability, such as nitrogen fixation, phosphorus solubility, and indoleacetic acid production, as well as enhance the plant's pH and manganese resistance ecological adaptability.

[0012] A soil conditioner containing the above-mentioned Paracoccus or a synthetic bacterial flora.

[0013] The soil conditioner is prepared by compounding the synthetic bacterial flora and organic materials, and the organic materials are prepared by simple composting and fermentation of agricultural waste (such as filter mud).

[0014] The number of effective bacteria in the soil conditioner is not less than 2.1×10 8 cfu / ml, and the ratio of Paracoccus C4-4 and C5-3 in the synthetic flora was 1:1.

[0015] The preparation method of the above-mentioned soil conditioner is as follows: 450-500 ml of bacterial dosage is applied per kilogram of organic material, and the bacterial agent is sprayed and mixed with the organic material in the tank, and then balanced for at least seven days; the bacterial agent is sprayed and mixed for the second time under the same conditions, and the mixture is balanced for seven days to obtain the soil conditioner.

[0016] In response to the problems existing in acidic soil improvement, the inventors screened and isolated Paracoccus communis C4-4 and C5-3 from the environment, with a preservation number of CGMCC NO:31971, a classification name of Paracoccus communis, and a preservation number of CGMCC NO:31972, a classification name of Paracoccus communis. Studies have shown that Paracoccus communis C4-4 and C5-3 of the same genus and species have strong ecological adaptability and good growth-promoting ability, and can improve the soil environment in combination with organic materials. Based on this, the inventors constructed a synthetic bacterial community constructed with Paracoccus communis, including the above-mentioned two strains of Paracoccus communis C4-4 and C5-3. Experiments have shown that the synthetic bacterial community includes the advantages of strains C4-4 and C5-3, and the bacterial community has a higher alkali production and growth-promoting ability; it has good ecological adaptability, a pH adaptation range of 4 to 8, and resistance to manganese stress of up to 5000 μmol / L; it can significantly increase the pH of the culture medium, and the alkalinization effect is obvious. Furthermore, the inventors used synthetic bacterial flora as a bacterial agent and compounded it with organic materials to prepare a soil conditioner that can improve acidic soil and promote plant growth. The conditioner is applied to acidic and lean soil, which can significantly increase soil pH, increase soil organic matter and nitrogen, phosphorus and potassium content, and promote root growth. Therefore, the present invention can be applied to the improvement of acidic and lean farmland soil.

[0017] Compared with the prior art, the present invention has the following outstanding advantages:

[0018] The synthetic bacterial community of the present invention can reproduce rapidly under low carbon source conditions and has the ability to produce alkali and promote growth. Compared with Bacillus sp., under low carbon source utilization conditions, the reproduction amount and alkalization effect of C4-4 bacteria and C5-3 bacteria are better than Bacillus sp., and they have strong growth-promoting ability and strong ecological adaptability.

[0019] The soil conditioner of the present invention includes organic materials, which can increase the organic matter content of the soil, improve the air permeability and water holding capacity of the soil, enrich the porosity of the soil, provide mineral nutrients for crops, increase the diversity of microorganisms, and promote plant growth after returning to the field.

[0020] The soil conditioner of the present invention utilizes the strong ecological adaptability and growth-promoting performance of the C4-4 and C5-3 strains to regulate crop rhizosphere microorganisms, greatly improves the root characteristics of crops, and promotes plant growth.

[0021] The soil conditioner of the present invention can increase the organic matter content and nutrient content in the soil, promote the growth of plants and soil microorganisms, improve the soil structure, increase the soil pH value, and solve the problem of low organic matter content in acidic soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1The single colony morphology characteristics and phylogeny spectrum of the Paracoccus of the present invention are shown in the figure: a Paracoccus C4-4, b Paracoccus C5-3.

[0023] Figure 2 The graph is a growth curve and pH change diagram of Paracoccus C4-4, C5-3 and their synthetic bacterial flora under low carbon source conditions, wherein: a is a growth curve, and b is a pH change.

[0024] Figure 3 The growth-promoting properties of Paracoccus sp. C4-4 and C5-3 of the present invention are compared with those of Bacillus sp. under pure culture conditions. In the figure: a nitrogen fixation, b phosphorus solubilization, and c IAA production.

[0025] Figure 4 This is a graph showing the ecological adaptability results of Paracoccus C4-4, C5-3 and the synthetic bacterial community of the present invention under Mn and different pH values, wherein: a is Mn adaptability, b is pH adaptability.

[0026] Figure 5 This is a graph showing the effect of the soil conditioner prepared by the synthetic bacterial community of the present invention on the pH and nutrients of acidic lean soil, wherein: a shows the planting effect of improved soil, b shows pH, c shows the nutrient content, and d shows the organic carbon.

[0027] Figure 6 This is a diagram showing the effect of the soil conditioner prepared by the synthetic bacterial community of the present invention on the agronomic traits of plants, wherein: a is a root system scan, b is root characteristics, c is plant height, and d is fresh weight.

[0028] Storage Information

[0029] <1> C4-4

[0030] The classification name is Paracoccus communis, the deposit number is CGMCC NO:31971, the deposit date is September 20, 2024, the deposit address is: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postal Code 100101, the deposit unit is: General Microbiology Center, China Culture Collection Administration.

[0031] Storage conditions: Ultra-low temperature freezing method or freeze drying for long-term storage

[0032] Colony morphology and growth conditions: C4-4 bacteria are round, yellow, with a rough, raised, moist surface and neat edges; the strain can grow at room temperature (25-35°C), with a pH tolerance range of 5-8, and enters a stable growth phase after 18 hours of culture in liquid LB medium.

[0033] <2> C5-3

[0034] The classification name is Paracoccus communis, the deposit number is CGMCC NO:31972, the deposit date is September 20, 2024, the deposit address is: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postal Code 100101, the depository unit is: General Microbiology Center, China Culture Collection Administration.

[0035] Storage conditions: Ultra-low temperature freezing method or freeze drying for long-term storage

[0036] Colony morphology and growth conditions: C5-3 bacteria are round, light yellow, with a rough, raised, moist surface and neat edges; the strain can grow at room temperature (25-35°C), with a pH tolerance range of 5-8, and enters a stable growth phase after 18 hours of culture in liquid LB medium. DETAILED DESCRIPTION

[0037] Example 1 Isolation and purification of alkali-producing C4-4 and C5-3 bacteria using low-carbon sources and high efficiency

[0038] In order to improve the highly acidic red sugarcane field, increase soil pH and organic carbon, restore the soil biological network, and promote plant growth, we isolated highly efficient carbon utilization alkali-producing and growth-promoting bacteria from the highly acidic red soil sugarcane field with an organic matter (carbon) content of only 12g / kg, in order to obtain bacteria that reproduce quickly under oligotrophic conditions, have strong ecological adaptability, and have an alkalizing effect. The specific operations are as follows:

[0039] (1) Enrichment: Acid-lean red soil (source: Nanning, Guangxi) was collected. 100 ml of LB liquid culture medium (10 g / L peptone, 10 g / L NaCl, 5 g / L yeast) was prepared in a 250 ml Erlenmeyer flask and sterilized at high temperature. 5 g of fresh soil sample was added to the above culture medium and cultured on a constant temperature air bath shaker at 30°C and 150 rpm for 24 hours. 5 mL of the above enrichment culture solution was transferred to the same sterilized liquid LB culture medium and repeated three times.

[0040] (2) Isolation of low-carbon source efficient utilization bacteria on plates: In order to obtain efficient utilization bacteria under low-carbon source conditions, 1 mL of the third enrichment culture solution was taken and diluted 10% with sterile water. -3 , 10 -4 , 10 -5Then, take 0.1 ml of the dilution and spread it evenly on the low-carbon source solid culture medium (the formula is 0.02g MnSO4, 1g Na2HPO4, 1.8g KH2PO4, 0.4g MgSO4, 0.05gCaCl2, 0.5g NH4Cl, 0.02g FeCl3, 10.0g Na2S2O3, 1.0g NaCl, 1L distilled water, 2.75g glucose (0.1% C), 15g agar) by plate spreading. Place the coated plate in a 30°C constant temperature incubator and culture for 48 hours. After the colonies are formed, select larger single colonies and purify them by 4-zone plate streaking separation or dilution plating method, and finally obtain 2 strains of carbon source efficient utilization bacteria. The purified single strains were stored in 20% glycerol and placed at -80°C. The morphological characteristics of single colonies are shown in Figure 1 .

[0041] (3) Screening of bacteria with high efficiency in utilizing low carbon sources: The purified single bacteria were inoculated into a liquid culture medium containing a low carbon source (the formula was 0.02 g MnSO4, 1 g Na2HPO4, 1.8 g KH2PO4, 0.4 g MgSO4, 0.05 g CaCl2, 0.5 g NH4Cl, 0.02 g FeCl3, 10.0 g Na2S2O3, 1.0 g NaCl, 1 L distilled water, 2.75 g glucose (0.1% C), 15 g agar), and cultured at 30°C, 150 r / min for 4 days. The growth OD600 value of the bacteria was measured, and the C content in the culture medium was measured.

[0042] (4) Classification and identification of alkali-producing bacteria that efficiently utilize low-carbon sources: The strains with high tolerance and oxidation function were screened out using 16S rRNA, that is, the prokaryotic 16S rRNA universal primers 27F (5′AGAGTTTGATCMTGGCTCAG3′, SEQ.ID.NO.3) and 1492R (5′GGYTACCTTGTTACGACTT3′, SEQ.ID.NO.4) were used for PCR amplification of their 16S rRNA (the PCR reaction procedure was: pre-denaturation at 98°C for 2 min, 98°C for 10 s, 54°C for 10 s, 72°C for 15 s, 25 cycles, and extension at 72°C for 2 min). After the PCR products were detected by 1% agarose gel electrophoresis, they were directly sent to Shanghai Meiji Biopharmaceutical Technology Co., Ltd. for sequencing. Then, they were compared with the international NCBI GenBank (www.ncbi.nlm.nih.gov) nucleotide database. The results showed that the nucleotide homology was 100%. Both strains were identified as Paracoccus communis C4-4 and Paracoccus communis C5-3. Their lineages were: Bacteria (bacteria)-Pseudomonadota (Pseudomonas)-Alphaproteobacteria (α-Proteobacteria)-Rhodobacterales (Rhodobacterales)-Paracoccaceae-Paracoccus (Paracoccus). Although they are bacteria of the same genus and species, their morphological characteristics, physiological and biochemical characteristics have obvious differences. Paracoccus communis C4-4 and C5-3 are the first reported carbon source efficient utilization alkali-producing bacteria and growth-promoting bacteria in different subspecies. The 16s rRNA gene sequence is shown in the sequence listing SEQ.ID.NO.1 and SEQ.ID.NO.2, and the phylogenetic spectrum constructed based on the gene sequence is shown in Figure 1 .

[0043] Example 2 Growth characteristics of C4-4, C5-3 and synthetic bacterial flora

[0044] Preparation of strain seed solution: The strain was inoculated in a low-carbon source liquid culture medium and cultured for 24 hours. The cells were centrifuged at 8000 r / min for 10 minutes, and the cells were collected. The cells were washed twice with 0.8% NaCl solution and resuspended. The OD was adjusted to 1.0 and the following studies were carried out.

[0045] (1) Growth curves of C4-4, C5-3 and synthetic bacterial flora: Seed solution was inoculated at 1% (v / v) into a conical flask containing 100 ml of low carbon source liquid culture medium (adjusted to pH 7.2), and cultured in a shaking incubator at 35°C and 150 r / min. Optical Density 600 (OD600) of the solution was measured at different time points, and each treatment was repeated 3 times. The growth curves of C4-4, C5-3 and synthetic bacterial flora are shown in Figure 2 . It can be seen from the figure that the strain is in the adaptation period in the first 18 hours, and then enters the logarithmic period, and the OD value is stable above 1.2. Among them, C4-4 grows slower than C5-3 in the first 70 hours, and then grows faster, and the OD value in the stable period is higher than C5-3. The growth of the bacterial community synthesized by the two is basically the same as that of a single bacterium.

[0046] In practical applications, faster growth of strains under low carbon sources means larger microbial biomass obtained under the same C conditions, stronger ecological adaptability, and better ability to exert the functions of the strains.

[0047] (2) Analysis of alkali production during the growth of C4-4, C5-3 and synthetic bacterial consortia: Seed solution was inoculated at a 1% (v / v) inoculum into a conical flask containing 100 ml of low carbon source liquid culture medium (adjusted to pH 7.2), and cultured in a shaking incubator at 35°C and 150 r / min. Samples were taken at different time points to measure the pH of the solution. Each treatment was repeated 3 times. The pH values ​​of the culture medium of C4-4 and C5-3 are shown in Figure 2 The results showed that the pH of the culture solution of strain C4-4 gradually increased and stabilized at above 8.0, while the pH of the culture solution of C5-3 stabilized at around 7.0. Both had a certain alkalinization effect, but the alkalinization effect of C5-3 was more obvious, indicating its potential to increase soil pH when used as a bacterial community in actual acidified soils. The pH of the synthetic bacterial community treatment was basically the same as that of C4-4, but during the stable period, the pH was slightly higher than that of C4-4, indicating that the synthetic bacterial community had more prominent alkali secretion performance.

[0048] Example 3 Growth-promoting properties of C4-4, C5-3 and synthetic bacterial flora

[0049] In order to understand the potential growth-promoting properties of C4-4, C5-3 and synthetic bacterial communities on plants, including the ability to fix nitrogen, solubilize phosphorus and produce IAA, the nitrogen-fixing ability was determined by growth in Ashby liquid medium; the phosphorus solubilizing ability was determined by growth in PKO medium; and the IAA content was determined by Salkowski colorimetric method. The seed solution (1%) was inoculated in the medium for low-carbon source growth promotion test, and the OD600 of the solution was sampled to represent the phosphorus solubilizing and nitrogen-fixing ability; the IAA was sampled to represent the indoleacetic acid production ability.

[0050] like Figure 3As shown in the figure, the results showed that B1 (Bacillus sp.), C4-4, C5-3 and synthetic bacterial communities all had good nitrogen fixation ability, with no significant difference between the treatments, and their biomass gradually increased with the growth time, indicating that microorganisms can fix nitrogen in the air. The phosphorus dissolution experiment showed that B1 bacteria had better phosphorus dissolution, while C4-4 and C5-3 had relatively weak phosphorus dissolution, while the phosphorus dissolution of the synthetic bacterial community was significantly enhanced, which was equivalent to that of B1 bacteria. C5-3 had a strong ability to produce IAA, reaching 38 mg / L after 5 days of cultivation, while B1 and C4-4 had low IAA production capabilities, while the synthetic bacterial community had a very significant improvement in IAA production capabilities. Therefore, on the whole, the synthetic bacterial community has better growth-promoting potential.

[0051] Example 4 Ecological adaptability of C4-4, C5-3 and synthetic bacterial flora

[0052] In order to understand the ecological adaptability of strains C4-4 and C5-3 and the synthetic bacterial community in soil, including the adaptability under soil pH and Mn stress factors, the activated bacterial suspension was inoculated at 1% of the inoculum into soils with different pH values ​​(4.0, 4.5, 4.8, 5.0, 6.0, 7.0, 8.0), Mn concentrations, and pH values. 2+ The culture was cultured in a carbon-fixing liquid culture medium with 0.1% carbon source (0, 100, 500, 1000, 5000 μmol / L) at 150 rpm for 0 h, 12 h, 24 h, 36 h, 48 h, 72 h, 84 h, and 96 h, and samples were taken to measure OD600 and pH.

[0053] like Figure 4 As shown, the research results show that the C4-4 and C5-3 strains and the synthetic bacterial community have a wide pH adaptability range and can grow normally between 4-9; the tolerance to Mn is high, up to 5000μM. Therefore, under the adverse conditions of low pH and high Mn content usually present in acidic lean red soil, the synthetic bacterial community of the present invention can grow better.

[0054] Example 5 Improvement of acidic red soil by using soil conditioner prepared by synthetic bacterial consortium constructed by C4-4 and C5-3

[0055] Preparation of soil conditioner: First, Bacillus sp., C4-4 strain and C5-3 strain were expanded and cultured to the logarithmic phase, centrifuged at 8000rpm for 8min, washed three times with sterile physiological saline and resuspended (OD600=1.0) to obtain bacterial solution. Using filter mud as the matrix, the bacterial solution was applied in small amounts of 450-500 ml of bacterial solution per kilogram of organic material and sprayed evenly on the matrix several times, mixed and balanced for at least seven days; the same steps were performed for the second mixing, and after balancing for seven days, a soil conditioner mainly composed of Paracoccus was obtained (i.e., the treatment group of the present invention), and the moisture content of the organic material was maintained at about 40% during the whole process.

[0056] The experiment used a potted test in a greenhouse. The test soil was a strongly acidic red soil with a pH of 4.8 and only 12g / kg of organic matter. The test soil was fully mixed with compound fertilizer (NPK=15-15-15, with an application rate of 0.3g / kg as base fertilizer) and balanced in a wet state for 7 days. The above soil conditioner was added at an addition rate of 5g / kg, and 1.5kg was weighed and placed in a plastic pot (top diameter 15cm×bottom diameter 13cm×height 12cm) after mixing evenly. Each treatment was repeated 3 times, and the soil moisture content was kept at 70% of the maximum water holding capacity in the field by weighing method, and balanced for 1 day. The treatment without adding substrate and the treatment with only adding substrate were used as the control group. After the soil balance was completed, 3 or 4 strong and uniformly growing lettuce seedlings (4 true leaves) were transplanted into the soil. The potted mass was recorded after the transplanting was completed, and based on this, the evaporated water was supplemented every 2 days with tap water by weighing method. In the early growth stage (10th day) and the middle growth stage (25th day), topdressing was performed once, with the amount of topdressing being 0.1g / kg urea, and compound fertilizer was applied at the bottom in the form of solution. The lettuce was harvested one month later. When the lettuce in the potted experiment was harvested, the rhizosphere soil and non-rhizosphere soil samples of the plants were collected to measure the soil pH, nitrogen, phosphorus, potassium and organic matter content. The whole plant sample was collected, the fresh weight was weighed, and the roots were cut after measurement to analyze the root morphology, including the total root length and root surface area.

[0057] Soil pH, nitrogen, phosphorus, potassium and organic matter content can effectively evaluate the effect of biological organic materials on the physical and chemical properties of acidic lean soil. Figure 5 As shown, the application of the present invention improves the pH, nitrogen, phosphorus, potassium and organic matter content of the soil, indicating that the improvement effect of the bacterial flora is more obvious.

[0058] Depend on Figure 6 It can be seen that the increase in lettuce biomass is the result of the combined action of the microbial agent and organic materials. The biomass of lettuce treated with only substrate was significantly increased compared with the treatment without substrate. On this basis, the addition of microbial agents significantly increased the biomass of lettuce, especially the root morphology indicators of lettuce, indicating that the alkali-producing growth-promoting characteristics of the strain greatly improved the agronomic traits of crops in acidic and lean soils.

[0059] To sum up, biological organic materials mainly composed of Paracoccus can utilize the alkali-producing growth-promoting characteristics of the strains, combined with the improvement effect of organic matter provided by organic materials, and can significantly improve the acidic and lean soil, such as the red soil in the highly acidic sugarcane field, increase its pH value and organic matter, and have important practical application value.

Claims

1. A strain of Paracoccus communis C4-4 or C5-3, which has a deposit number of CGMCC NO: 31971 and a taxonomic name of Paracoccus communis, or a deposit number of CGMCC NO: 31972 and a taxonomic name of Paracoccus communis.

2. The Paracoccus according to claim 1, characterized in that The 16S rRNA gene thereof has the base sequence of SEQ.ID.NO.1 or SEQ.ID.NO.2 in the sequence list.

3. A synthetic bacterial colony constructed with Paracoccus, characterized in that It includes the two strains of Paracoccus C4-4 and C5-3 described in claim 1.

4. Use of the Paracoccus described in claim 1 or the synthetic bacterial flora described in claim 3 in soil improvement or plant growth promotion.

5. The use according to claim 4, characterized in that: The soil is acidic lean soil, and the plant is lettuce.

6. A soil conditioner, characterized in that Contains the Paracoccus as described in claim 1 or the synthetic bacterial flora as described in claim 3.

7. The soil conditioner according to claim 6, characterized in that The synthetic bacterial flora according to claim 3 is compounded with organic materials, wherein the organic materials are obtained by simple composting and fermentation of agricultural waste.

8. The soil conditioner according to claim 7, characterized in that The number of effective bacteria in the soil conditioner is not less than 2.1×10 8 cfu / ml, and the ratio of Paracoccus C4-4 and C5-3 in the synthetic bacterial flora was 1:

1.

9. The method for preparing the soil conditioner according to claim 6, characterized in that: Apply 450-500 ml of bacterial dosage per kilogram of organic material, spray the bacterial agent and the organic material in the tank to mix evenly, and then balance for at least seven days; spray the bacterial agent for the second time under the same conditions, and balance for seven days to obtain the product.

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