Starry-sky algae LC8 from desertification region and application of starry-sky algae LC8

Abstract

The invention belongs to the field of microorganisms, and discloses a strain of Coelastrus sp. LC8 separated from biological crust soil in a karst rocky desertification region, and the preservation number of the strain is CGMCC No. 41199. The starry-sky algae are high in growth and reproduction speed and high in exopolysaccharide content and soluble protein content, and after algae liquid prepared from the algae species is applied to barren sandy soil and loam, the soil water-retaining property can be improved, the soil erosion resistance can be enhanced, soil nutrients can be improved, and the soil carbon sequestration capacity can be improved. In addition, the application of the algae liquid can promote plant growth and nutrient absorption, so that the algae liquid is combined with the plants to perform efficient ecological restoration and treatment on the degraded land. The application of the invention can reduce the application cost of ecological restoration engineering, is good for the environment, and realizes sustainable and healthy development of the ecological environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microorganisms, and particularly relates to isolation and screening of biological crust algae and application thereof, and especially to a biological crust soil starry algae and application thereof in ecological restoration of degraded soil. BACKGROUND

[0002] Desertification is a land ecosystem degradation process driven by natural and human factors such as climate change, overexploitation and vegetation destruction, mainly occurring in arid, semiarid and subhumid arid regions, and specifically showing various forms such as land desertification, stone desertification and salinization. As one of the most serious ecological challenges in the world, desertification not only leads to sharp reduction of land productivity, loss of biodiversity, frequent natural disasters such as sandstorms, but also directly threatens regional food security and human living and development space.

[0003] China is one of the countries most seriously affected by desertification. As of the latest data, the area of desertification land is 257.37 million square kilometers, accounting for 26.81% of the land area, and the degraded soil generally has problems such as lack of organic matter, loose structure, poor water and fertilizer retention capacity, making ecological restoration extremely difficult. Although China has achieved "zero growth" of land degradation through key projects, the existing restoration technologies still have obvious limitations: physical measures (such as sand-fixing grids) are high in cost and difficult to form a self-sustaining ecosystem; chemical amendments are easy to cause secondary pollution; traditional biological restoration relies on artificial vegetation planting, which not only has low survival rate, but also is difficult to adapt to extremely barren degraded environment, especially lacking core technologies that can quickly improve soil microenvironment and promote natural restoration of native vegetation.

[0004] Biological crust, as an important ground cover in arid and semiarid regions, is formed by biological communities such as algae, moss, bacteria and their secretions, and in the long evolution process of desert ecosystems, biological crust shows great ecological value in maintaining the stability of desert systems, promoting nutrient cycling, inhibiting soil erosion and wind erosion, regulating the effectiveness and redistribution of water resources, assisting the establishment and continuous survival of vascular plants, and promoting the restoration of desert vegetation. The evolution of biological crust often follows the sequence of algal crust, lichen crust and moss crust, and in specific ecological environments, it may directly jump from algal crust to moss crust. Biological crust is an important indicator of soil fixation in desertification areas, and it can form microhabitats in harsh environmental conditions to create favorable conditions for plant colonization and growth.

[0005] However, the natural biological soil crust grows slowly (usually for several years to several decades), and the existing high-throughput sequencing results show that there are a large number of algae in the biological soil crust at different succession stages, which are the first peak species and the core microbial group for the formation, evolution and functional role of the biological soil crust. Algae can produce extracellular polysaccharides and extracellular soluble substances, and have photosynthetic carbon fixation characteristics, which play a direct role in improving soil structure, increasing soil nutrients, and strengthening soil carbon sequestration, and an indirect role in promoting the growth of other soil microorganisms and plants. In addition, the biological soil crust growing in the desertification area means that the coexisting microorganisms may have strong environmental adaptability. Therefore, it is of great significance to enrich the algal species resource library and obtain effective ecological restoration microbial groups that adapt to difficult habitats by screening algae from the biological soil crust growing in the desertification area. SUMMARY

[0006] The purpose of the present application is to provide a strain of Coelastrella sp. isolated from the soil of desertification biological soil crust and its application in degraded land. The strain is isolated from the soil of biological soil crust in the karst rocky desertification area, has a fast growth and reproduction speed, produces a high amount of extracellular polysaccharides and soluble proteins, and has the effects of improving soil physical properties, increasing soil nutrients and organic carbon, enhancing water retention performance, and promoting plant growth. The strain has strong adaptability to dry and nutrient-poor environments, breaks through the problem of unstable and unsatisfactory ecological restoration effect caused by weak environmental adaptability in the application of existing microbial agents, realizes a new ecological restoration mode of "controlling organisms with organisms", provides a new solution for efficient and sustainable restoration of degraded soil, and has the advantages of environmental friendliness and low cost. Thus, the present application is completed.

[0007] Therefore, the present application first provides a strain of Coelastrella sp. isolated from the soil of biological soil crust in the karst rocky desertification area, which has a preservation number of CGMCC No. 41199. In the present application, the strain is named Coelastrella sp. LC8, and was preserved in the China General Microbiological Culture Collection Center (CGMCC) on July 5, 2024, with a preservation number of CGMCC No. 41199. The strain is classified and named as Coelastrella sp.

[0008] The present application further provides the application of the Coelastrella sp. in soil water retention. Specifically, the application is to apply the algal liquid of the Coelastrella sp. to the soil. In particular, the soil is sandy soil.

[0009] In the specific embodiment, 10 6 to 10 8 algal cells per kilogram of soil are applied.

[0010] Experiments show that the soil water content of the application of the starry algae algal liquid is relatively slow, and the soil water content is still high at the 4th week, which shows that the application of the algal liquid can improve the water retention performance of sandy soil.

[0011] The application also provides the application of the starry algae in soil improvement.

[0012] Specifically, the application is the improvement of organic matter content and / or the increase of soil nutrients and / or the improvement of soil structure.

[0013] More specifically, the soil nutrients refer to soil nitrogen, phosphorus and potassium nutrients, and the indicators of the soil structure are the average mass diameter and the geometric mean diameter. In particular, the application is suitable for sandy soil.

[0014] Experiments have proved that the application of starry algae plays an important role in improving the water retention performance of sandy soil, improving the organic matter and nutrients of sandy soil, and stabilizing the physical structure of sandy soil, and provides excellent microbial resources for desertification land ecological restoration engineering, which has important significance.

[0015] In summary, the present application aims at the pain points of low biological repair efficiency and poor adaptability in the prior art, and innovatively selects functional algae with the characteristics of "fast growth, high extracellular polysaccharide and soluble protein output" from biological crust. By strengthening the rapid colonization ability of algae, the formation of biological crust can be accelerated; the extracellular polysaccharide secreted by the algae can improve the soil aggregate structure and enhance the water retention, and the soluble protein can improve the soil organic matter content, providing a basis for subsequent vegetation restoration. This technical path breaks through the problem of unstable and unsatisfactory ecological restoration effect caused by weak environmental adaptability in the application of existing microbial agents, realizes a new ecological restoration mode of "controlling biology with biology", and provides a new solution for efficient and sustainable restoration of degraded soil. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 , Algal distribution in different biological crust soils.

[0017] Figure 2 , Growth rate curve of algal strains.

[0018] Figure 3 , Soluble protein content of LC8 and EMC7.

[0019] Figure 4 , Extracellular polysaccharide content of LC8 and EMC7.

[0020] Figure 5 , Water retention of sandy soil by application of starry algae LC8.

[0021] Biological material preservation information: the starry sky algae LC8 of the present application was preserved in the China General Microbiological Culture Collection Center (CGMCC) on July 5, 2024, and the preservation number is CGMCC No. 41199, and the classification name is Coelastrella sp. DETAILED DESCRIPTION

[0022] 1. Determination of soil algae in different habitats of biological soil crust in desertification area

[0023] 1.1 Source of biological soil crust material and sample collection

[0024] The biological soil crust was collected in Jianshui County, Honghe Hani and Yi Autonomous Prefecture, Yunnan Province (103°57'E, 23°09'N). The study area is a karst rocky desertification area with no obvious vegetation and an altitude of 1500 m. It belongs to a typical south subtropical monsoon climate region with an average annual temperature of 19.8°C and an annual precipitation of about 805 mm, mainly concentrated in July-August. There are no frost days throughout the year, totaling 307 days. This study selected areas with little external interference, similar topographic features, and high stability of biological soil crust as the research object. Five sampling points were arranged with a distance of more than 2 meters between each sampling point according to the principle of random distribution. Random sampling method was used to repeat sampling of biological soil crust samples at different development stages, including algal crust (BC1, BC2, BCS3), lichen crust (BC4, BC5, BCS6), and moss crust (BC7, BC8, BCS9). The sampling area of each sampling point was 15 cm x 15 cm with a thickness of 3-4 cm. The crust layer was stripped with a sterile small shovel, and the remaining soil samples were collected. The soil samples were sieved through a 2 mm sieve to remove roots and debris, and the collected samples were stored in a -80°C ultra-low temperature freezer and a 4°C refrigerator for microbial high-throughput sequencing and isolation of crust algae.

[0025] 1.2 Extraction and PCR amplification of soil DNA

[0026] DNA of the soil stored at -80 °C was extracted using a FastDNA® spin kit (MP bio, Santa Ana, USA) kit according to the instructions, and after extraction, the DNA quality of the sample was detected by 1% agarose gel electrophoresis. The fungal specific gene amplification was performed on the DNA sample of qualified quality, and the amplification region was ITS1 region. The PCR reaction system was: Phusion Master Mix (2x) 15 μL; Primer (2 μM) 3 μL; Template DNA 10 μL; H2O 2 μL, a total of 30 μL. The reaction program was: 98 °C pre-denaturation for 1 min; 30 cycles including (98 °C, 10 s; 50 °C, 30 s; 72 °C, 30 s); 72 °C re-extension for 5 min.

[0027] 1.3 High-throughput Illumina MiSeq sequencing and analysis

[0028] The PCR product was purified by 2% agarose gel electrophoresis, the main band size of 400-450 bp was recovered, and the Thermo Scientific GeneJET gel recovery kit was used for recovery. Then the library was constructed, and after Qubit quantification and library detection, the Illumina Miseq-PE300 sequencing platform was used for sequencing. According to the sequence length, quality, primer and label, QIIME (version 1.17) was used to analyze all data sets; select raw sequences and delete low-quality sequences. Use UPARSE (V7.1) to classify the sequence set into multiple operational taxonomic units (OTUs), and the OTU annotation is based on the Silva database. The high-quality sequences of all samples are clustered into OTUs with 97% similarity. At the level of species taxonomic composition, through various unsupervised, supervised sorting, clustering and modeling methods, combined with the corresponding statistical test methods, the species abundance composition difference between different sample groups is further measured, and the marker species is tried to find. Calculate the distance matrix of each sample, and through various unsupervised sorting, clustering methods, combined with the corresponding statistical test methods, measure the beta diversity difference and significance between different sample groups. According to the composition distribution of species in each sample, construct a correlation network, calculate the topological index, and try to find out the key species.

[0029] From Figure 1As a result, all kinds of biological crusts, including algal crust (BC1, BC2, BCS3), lichen crust (BC4, BC5, BCS6), moss crust (BC7, BC8, BCS9) contain rich eukaryotic algae, and the dominant algae are Protoderma, Coelastrella, Tetracystis, etc. This result provides theoretical support for the follow-up screening of algae isolation.

[0030] 2. Isolation of algal strains in biological soil crusts

[0031] 1.1 Isolation and purification of crust algae

[0032] BG11 liquid medium (formula as follows: 1.5 g NaNO3, 0.04 g K2HPO3·3H2O, 0.075 g MgSO4·7H2O, 0.036 g CaCl2·2H2O, 0.006 g citric acid, 0.006 g ferric ammonium citrate, 0.001 g EDTA-Na2, 0.02 g Na2CO3, 1 mL trace elements, 1 L distilled water) was prepared, and the pH range of BG11 liquid medium was adjusted to 7.0 to 7.2, and sterilized at 121 ℃ for 15 min. 30 mL of BG11 liquid medium was added to each 50 mL sterilized conical flask, and the biological crusts stored in the 4 ℃ refrigerator were uniformly mixed into a sample according to the same development stage. 1 g of sieved crust soil sample was weighed, and the soil suspension was fully mixed in a 180 rpm shaker for 30 min, and then placed in a 27 ℃, 2700 lx light enrichment culture. The soil suspension was shaken for 1 minute at a fixed time every day, and after 2 weeks of culture, it was gradient diluted to 1×10 3 -1×10 6, respectively, into 96-well plates, 200 μL per well, and continue to culture for 2 weeks, select about 30% of different wells in the 96-well plate to appear visible green gradient dilution treatment, use sterilized toothpick to fully stir in the green well and then streak on BG11 solid culture medium (add 18 g / L agar to the above-mentioned BG11 liquid culture medium), place in a light incubator at 27 ℃, light 2700 lx for 2-3 weeks, observe the purity of the culture, continue to streak and purify by picking single colony culture to new BG11 solid culture medium, observe the morphology of algae on the plate, until the morphology of green algae on the plate is consistent and there is no bacterial contamination, which can be preliminarily determined as pure algae, and further confirmed as pure algae strain by optical microscope observation, then pick single algae on the plate with a sterile toothpick and place in BG11 liquid culture medium for 2 weeks, shake for 2 minutes every day at a fixed time, obtain pure algae liquid, mix with 30% glycerol at a ratio of 1:1, and place in a -80 ℃ ultra-low temperature refrigerator for preservation of the algae strain.

[0033] Through the above steps, a total of 25 pure algae strains were isolated. Among them, 10 pure algae strains were isolated from soil with algae crust, 8 pure algae strains were isolated from soil with lichen crust, and 7 pure algae strains were isolated from soil with moss crust.

[0034] 2. Biological characteristics of crust algae

[0035] 2.1 Culture and growth determination of crust algae

[0036] The 25 pure algae strains preserved at low temperature were streaked on BG11 solid culture medium, and cultured in a light incubator at 27 ℃, light 2700 lx for 3 weeks, then single algae was picked with a sterile toothpick and inoculated in 30 mL BG11 liquid culture medium, and cultured at 27 ℃, light 2700 lx, with shaking for 2 minutes every day at a fixed time, and the OD680 value was determined after 4 weeks of culture to preliminarily judge the growth status of the algae strain.

[0037] The two algae with the highest OD680 values were selected for growth rate monitoring, 1 mL of each of the two algae liquids fermented for 28 days was inoculated in 30 mL BG11 liquid culture medium, and cultured in a light incubator at 27 ℃, light 2700 lx, the OD680 value was determined at the first time of starting culture, recorded as 0 days, and then determined every 24 h until the OD value of the algae fermentation liquid was stable and showed a downward trend, with culture time as the horizontal coordinate and OD680 value as the vertical coordinate, the growth curve of the selected algae strain was drawn.

[0038] The results show that after 4 weeks of liquid culture, the growth of 25 pure algae, the top 2 are LC8 isolated from lichen crust and EMC7 isolated from moss crust. In order to further understand the growth rate of the strain algae, the whole growth cycle rate is monitored, and the results are shown in Figure 2 The growth of the two strains is basically consistent with time, and the OD680 value reaches the maximum at 29 days, among which the OD680 value of LC8 is 2.647, and the OD680 value of EMC7 is 2.5289 at this time, and then the OD value begins to decrease. Lichen crust is an intermediate transition stage of algae crust to moss crust, and LC8 strain is derived from lichen crust soil, and has the fastest growth rate, which may play an important role and significance in the succession and environmental adaptation of biological crust.

[0039] 2.2 Determination of soluble protein of different crust algae

[0040] Take 50 mL of algae liquid cultured for 28 days, centrifuge at 4000 r / min for 10 min to obtain algae precipitate, and place the obtained algae precipitate in a freeze dryer overnight to dry, and harvest the algae powder. Weigh 0.05 g of algae powder in a centrifuge tube, add distilled water to dilute 40 times, and use the BCA protein concentration determination kit to determine the soluble protein content.

[0041] The nitrogen element is contained in the soluble protein, which can be used as a nitrogen source for microbial growth and metabolism, and provides sufficient material basis for soil nitrogen nutrient transformation. The results are shown in Figure 3 The soluble protein content of the two algae strains is more than 1000 μg / mL, among which the soluble protein content of EMC7 is higher, followed by LC8, which reaches 1216.92 μg / mL and 1123.65 μg / mL, respectively.

[0042] 2.3 Determination of extracellular polysaccharide of different crust algae

[0043] The content of extracellular soluble polysaccharide is determined by anthrone sulfuric acid colorimetry. Prepare glucose standard solution (0.1 g / L), take several test tubes with stoppers, and add different proportions of glucose standard solution and prepared anthrone sulfuric acid solution into the test tubes according to the table. After adding the reagents, shake well, place in a boiling water bath for 15 min. After heating, take out and cool to room temperature. Determine the absorbance value of each tube at 620 nm with a microplate reader, and draw a standard curve according to the measured absorbance value. Take 1 mL of algae liquid to be tested, and determine the absorbance value at 620 nm according to the same method above, and calculate the content of extracellular soluble polysaccharide according to the standard curve.

[0044] Exopolysaccharide can be used as a carbon source for the growth and metabolism of soil microorganisms, and can promote the formation of soil macro-aggregates, thereby enhancing the soil erosion resistance and improving the soil water retention performance. The results are shown in Table 1, wherein the exopolysaccharide content of the two algae strains is more than 600 μg / mL, and the exopolysaccharide content of LC8 is the highest, reaching 651.32 μg / mL. Figure 4

[0045] 3. Molecular biological identification of LC8 algae strain isolated from biological soil crust

[0046] Lichen crust is an intermediate transition stage of biological soil crust development. The LC8 algae strain isolated therefrom not only has the fastest growth and reproduction speed, but also has the highest exopolysaccharide content and the highest amount of secreted soluble protein, which indicates that the algae strain has excellent comprehensive performance and may play an important role in subsequent application of the algae strain. Therefore, the LC8 algae strain is subjected to molecular biological identification, and the specific operation is as follows.

[0047] (1) Algae strain DNA extraction: 500 mL of algae liquid cultured for 2 weeks is used as an extraction sample, centrifuged at 8000 rpm for 5 min, and the algae precipitate is transferred to a 2 mL centrifuge tube, a small amount of quartz sand is added, and the mixture is oscillated on a high-speed cell crusher for 15 min. 800 μL of 2×CTAB extraction solution is added, and the mixture is placed in a 65 ℃ water bath for 1 h, centrifuged at 12000 rpm for 10 min, and the supernatant is taken out. An equal amount of chloroform-isopentyl alcohol mixed solution is added, and the mixture is shaken and mixed uniformly. After standing for 20 min, the mixture is centrifuged at 12000 rpm for 10 min, and the supernatant is retained. Double volume of pre-cooled anhydrous ethanol is added to the supernatant, and the mixture is mixed and transferred to -20 ℃ for standing for 30 min. The mixture is centrifuged at 12000 rpm for 10 min, and the supernatant is removed. 800 μL of 75% ethanol is added to the precipitate, and the mixture is centrifuged at 12000 rpm for 5 min and the supernatant is removed. The precipitate is naturally air-dried, 50 μL of distilled water is added, and the mixture is incubated at 37 ℃ for 30 min to dissolve. The obtained is the extracted algae strain DNA sample.

[0048] (2) DNA amplification and identification: three pairs of primers are selected to amplify the ITS, tufA and psbA genes, so as to accurately identify the algae species and determine the classification status thereof. The primers for the ITS are subjected to PCR reaction to amplify the ITS sequence. The PCR system includes 2.5 μL of primer, 5 μL of DNA template, 25 μL of 2×PCR mix and 15 μL of ddH2O. The amplification conditions are as follows: 94 ℃ pre-denaturation for 10 min, 30 cycles including 94 ℃ denaturation for 1 min, 58 ℃ annealing for 30 s, 72 ℃ extension for 2 min, and final 72 ℃ terminal extension for 10 min. ​

[0049] PCR reaction was carried out for amplifying tufA gene by using specific primers for tufA, 2.5 μL of each of the PCR system and primers, 5 μL of DNA template, 25 μL of 2x PCR mix, 15 μL of ddH2O, and the amplification conditions were as follows: 94 ℃ pre-denaturation for 10 min, 94 ℃ denaturation, 52 ℃ annealing and 72 ℃ extension for 1 min, 35 cycles, and finally 72 ℃ terminal extension for 5 min.

[0050] PCR reaction was carried out for amplifying psbA gene by using specific primers for psbA, 1 μL of each of the PCR system and primers, 2 μL of DNA template, 12.5 μL of 2x PCR mix, 8.5 μL of ddH2O, and the amplification conditions were as follows: 94 ℃ pre-denaturation for 5 min, 35 cycles including 92 ℃ denaturation, 57 ℃ annealing and 68 ℃ extension for 1 min, and finally 72 ℃ terminal extension for 10 min.

[0051] The three PCR products with clear bands were sent to Shanghai Biosciences for sequencing, and the returned sequences were subjected to blast sequence alignment on the NCBI website (https: / / blast.ncbi.nlm.nih.gov / Blast.cgi) to obtain the identification results.

[0052] The ITS, tufA and psb genes of the crust algae LC8 were amplified by using three pairs of specific primers, and the amplification products were sent to the company for sequencing. The gene sequences amplified by the three pairs of primers were subjected to blast sequence alignment on the NCBI website, and the website sorting was generally defaulted to arrange according to the size of E Value, and the smaller the value, the higher the sequence alignment reliability. Further, according to the alignment results, the sequence with the highest sequence length (Length) similarity and sequence comparison consistency (Per. Identities) was determined as the similar sequence, and the alignment results of the three pairs of genes showed that the similarity of the LC8 strain to the reference related bacteria was 89.32%, 96.54% and 91.52% respectively, indicating that the LC8 strain belonged to the genus Scenedesmus.

[0053] Table 1, Blast alignment results of different gene sequence amplification of crust algae LC8

[0054]

[0055] 4. Effect of application of starry algae LC8 on water retention of sandy soil

[0056] Land desertification is one of the main and typical types of desertification, characterized by sandy soil and nutrient depletion. Therefore, this study uses nutrient-poor sandy soil as the application target to characterize the application prospects of *Lycopodium clavatum* LC8 in desertification control. The sandy soil was collected from woodland in Huangfa Village, Daxing District, Beijing. After removing impurities, it was sieved through a 0.5 cm sieve, and 5 kg was placed in each pot (pot height 17.5 cm, diameter 25.5 cm). The algal solution, cultivated for 3 weeks, was diluted to 10% before application. 4 The algal cell count was 500 mL, and four treatments were implemented: one treatment with an equal volume of water and BG11 liquid medium as a control, and another treatment with an algal strain, EMC7, isolated from biological crusts as a control. Each group had 12 replicates, for a total of 48 basins. For the first two weeks after treatment, water was added daily to ensure consistent moisture levels in each basin. From the third week onwards, watering was stopped. Three basins were removed weekly to measure soil moisture content and compare the effect of algal application on soil water retention.

[0057] The results showed that ( Figure 5 In the first week, the soil moisture content of the treatment with *Alternaria solani* LC8 solution was not significantly different from the other three treatments. As time progressed, the soil moisture content of all four treatments gradually decreased, with the soil moisture content of the treatment with algal solution decreasing relatively slowly and remaining at a high level in the fourth week. The soil moisture content of the treatment with *Alternaria solani* LC8 solution was 13.4%, while the soil moisture content of the control treatments with added water and BG11 medium was 6.58% and 6.81%, respectively, representing increases of 83.41% and 74.64%. This indicates that the application of algal solution can improve the water retention capacity of sandy soils.

[0058] 5. The effect of applying Starry Sky Algae LC8 on improving sandy soil

[0059] Soil samples from the 6th week of each of the above experimental treatments were collected for analysis of soil aggregate stability, soil organic matter, soil nutrients, and extracellular polysaccharide content. The collected soil samples were divided into two parts: one part was sieved through a 1-2 mm sieve to remove impurities and used to determine available phosphorus (AP), available potassium (AK), available nitrogen (AN), organic matter (OM), and extracellular polysaccharides (EPS); the other part was undisturbed soil, used for determining soil aggregate stability.

[0060] The determination method of soil AP, AK, AN and OM refers to the soil agro-chemical analysis by Bao Shidan. The determination method of EPS is as follows: the soil sample is sieved through 0.25 mm, 1 g of which is added into 10 mL of 2 mol / L H2SO4, and then boiled in a water bath for 2 h, and then filtered while hot, and the filter tube is washed with hot deionized water for several times, and the filtrate and washing liquid are collected into a new digestion tube, 1 g of CaCO3 is added, and then filtered after no gas is generated, and the filtrate is collected and diluted to 20 mL to obtain a sample solution to be tested. 2 mL of the sample solution to be tested is taken into a dry and clean 10 mL centrifuge tube, 6 mL of anthrone reagent is immediately added, and then mixed and placed in a boiling water bath for 15 min, and then quickly taken out and immersed in an ice water bath for 15 min, and then the absorbance is measured at 620 nm. According to the calibration curve of glucose content, the concentration of sugar in the sample solution is calculated according to the absorbance of the sample solution, and the content of EPS is calculated. The determination of soil aggregate composition and stability is as follows: 200 g of soil sample is weighed and placed on a set of sieves with a pore size of 2 mm, 1 mm and 0.25 mm, and then the aggregate of >2 mm, 1-2 mm, 0.25-1 mm and <0.25 mm is separated, and then the mass of each particle size soil aggregate is weighed, and then the mass percentage of each particle size soil aggregate is calculated; the mean weight diameter (MWD) and the geometric mean diameter (GMD) are used to represent the stability of soil aggregate, and the higher the MWD and GMD values are, the greater the stability of the aggregate is, so the two indexes are calculated at the same time, and the specific formula is as follows:

[0061]

[0062] MWD = ∑ (wi x xi) / ∑ wi i wi is the mass percentage of the i-th particle size; xi is the average diameter of the aggregate. i The average diameter of the aggregate.

[0063]

[0064] GMD = exp[∑ (ln mi) / ∑ mi] i mi is the mass (g) of the aggregate of different particle sizes; m ’ The average diameter of the aggregate.

[0065] The core of soil improvement includes the improvement of soil organic matter content and the increase of soil nitrogen, phosphorus and potassium nutrients. In addition, soil physical structure is a key factor affecting soil fertility and material migration and transformation. Soil is composed of different particle size aggregates by the interaction between solid particles. Good aggregate structure is of great significance to the transformation of soil nutrients. Especially for sandy soil with low aggregation ability, promoting the formation and stability of soil aggregates is an important indicator to evaluate whether it is improved. From the results of Table 2 and Table 3, the two treatments of applying mat algae significantly improved soil organic matter and soil nutrients (see Table 2), soil structure improvement (Table 3), etc. Among them, the effect of starry algae LC8 was the best, and there was no significant difference between BG11 liquid medium treatment and water treatment, indicating that mat algae had a significant role in improving soil. Analysis showed that the organic matter (OM), total nitrogen (TN), total phosphorus (TP), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), and available potassium (AK) contents of the sandy soil treated with LC8 algae liquid were increased by 166.67%, 123.08%, 150.00%, 83.28%, 79.17%, and 44.86%, respectively, compared with the water treatment. In addition, extracellular polysaccharides (EPS) are polysaccharide substances secreted by microorganisms during growth and metabolism, which play an important role in the formation and stability of soil aggregates. They can increase soil adhesion and improve its physical structure, and at the same time provide carbon source and nutrients for other microorganisms in the soil, thereby increasing soil microbial diversity. As shown in Table 3, the EPS content in the sandy soil treated with starry algae LC8 was increased by 650.00% compared with the water treatment. The two main indicators for evaluating soil structure stability are mean weight diameter (MWD) and geometric mean diameter (GMD). The higher the MWD and GMD values, the greater the stability of the aggregates. The results showed that compared with the treatments of applying water or BG11 liquid medium, the application of LC8 algae liquid increased the content of super-large aggregates (>2 mm) in sandy soil and reduced the content of micro-aggregates (<0.25 mm). The MWD and GMD values were 0.59 and 0.43, respectively, which were significantly higher than those of the water and BG11 medium treatments and better than those of the EMC7 treatment.

[0066] Therefore, the application of starry algae LC8 plays an important role in improving the water retention performance of sandy soil, increasing the organic matter and nutrients of sandy soil, and stabilizing the physical structure of sandy soil. It provides excellent microbial resources for desertification land ecological restoration projects and has important significance.

[0067] Table 2, Effect of Starry Algae LC8 Application on Sandy Soil Nutrients

[0068]

[0069] Table 3. Effect of Starry sky algae LC8 application on sandy soil aggregate stability and its exopolysaccharides

[0070] .

Claims

1. A strain of Coelastrella sp. isolated from biological soil crusts in karst rocky desertification areas, characterized in that, and has a preservation number of CGMCC No. 41199.

2. Application of the star sky algae in soil water conservation according to claim 1.

3. Use according to claim 2, wherein the compound is ###0002### The application is to apply the algae liquid of the star sky algae in the soil.

4. Use according to claim 2 or 3, wherein the compound is ###0002### The soil is sandy soil.

5. The use according to claim 4, wherein the compound is ###0002### 10 6 to 10 8 algal cells per kg of soil.

6. Application of the star sky algae in soil improvement according to claim 1.

7. Use according to claim 6, wherein The application is to improve the content of organic matter and / or increase soil nutrients and / or improve soil structure.

8. Use according to claim 7, wherein the compound is ###0002### The soil nutrients refer to soil nitrogen, phosphorus and potassium nutrients.

9. The use according to claim 7, wherein the compound is ###0002### The indicators of the soil structure are the average mass diameter and the geometric mean diameter.

10. Use according to any one of claims 6 to 9, wherein The soil is sandy soil.

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