Cyanobacteria SCSIO17256 with high exopolysaccharide yield and application of cyanobacteria SCSIO17256 in erosion resistance of coral island

Abstract

The invention discloses cyanobacteria SCSIO17256 with high yield of exopolysaccharides and application of the cyanobacteria SCSIO17256 in erosion resistance of coral islands. The cyanobacteria is named as cyanobacteria Oculatus sp.SCSIO17256, and the preservation number of the cyanobacteria Oculatus sp.SCSIO17256 is CCTCC (China Center For Type Culture Collection) NO: M2025524. The cyanobacteria Ocularia sp.SCSIO17256 provided by the invention can effectively promote the formation of calcareous sand biological crust, has relatively strong sand consolidation capability and extremely strong anti-shearing capability, and can be applied to prevention and treatment of water and soil loss of coral islands and construction of coral island calcareous sand biological soil crust. Compared with physical sand consolidation, chemical sand consolidation and vegetation cultivation, microorganisms are used as a novel sand consolidation and crust cultivation mode, and the method has the advantages of being high in adaptability, low in cost, quick in effect and the like.

Description

Technical Field

[0001] The present invention belongs to the field of microorganisms, and particularly relates to a cyanobacterium Oculatella sp. SCSIO17256 with high extracellular polysaccharide production, its application in coral island anti-erosion, and the construction of biological soil crusts in coral islands. Background Art

[0002] Tropical coral islands are mainly coral islands with coral calcareous sand as the main substrate. Due to the lack of true soil and fresh water resources, it is difficult for vegetation to take root. Therefore, these coral reefs are regarded as the "deserts" in the ocean, and at the same time have extreme environmental characteristics such as high salt, strong alkalinity, high temperature, strong light, and serious soil erosion. The healthy soil resources and underground ecological fresh water resources of coral islands are the source of life that supports the animal and plant ecosystems of coral islands and realizes a livable environment. Biological soil crusts (BSCs), which have received much attention in desert ecosystems with similar extreme environments, have brought great inspiration for changing the "desert" state of coral islands. The composite biological soil crusts formed by the combination of organisms such as microorganisms, algae, mosses, and lichens and soil have characteristics such as drought tolerance, salt and alkali tolerance, carbon and nitrogen fixation ability, and strong reproductive ability. They can survive and reproduce widely in harsh environments and affect the surrounding microenvironment through their physiological and metabolic functions. Similar to the desert system, the BSCs in coral islands are also an important part of the coral island ecosystem, accounting for about 6.25% of the land area of coral islands. The generation and development process of BSCs is also the process of the primary succession of the most primitive vegetation. After experiencing a series of changes in physical, chemical, and biological properties, the desert soil is provided with the basic elements and conditions for plant growth, laying a foundation for the next succession process. BSCs play roles in many aspects such as soil processes, ecohydrology, and geochemical cycles, directly affecting rainfall infiltration, soil erosion, nutrient cycling, seed germination, biodiversity, etc., and playing an important role in the evolution process of the soil-water-vegetation system. Light energy-utilizing microorganisms are the most important functional components in BSCs. In particular, cyanobacteria with functions such as photosynthetic carbon fixation, nitrogen fixation, and polysaccharide production have always been considered the key groups for the formation and development of BSCs. However, research on cyanobacteria in biological crusts in tropical coral island areas is almost blank.

[0003] Cyanobacteria are a type of prokaryotes that contain chlorophyll and can perform photosynthesis, existing as single-celled or multi-celled organisms. They are the most important dominant group in biological soil crusts in arid and semi-arid regions. Their growth can provide rich nitrogen and carbon sources for the soil. In particular, the nitrogen fixed by some nitrogen-fixing cyanobacteria is an important source of nitrogen in desert soils. As important nitrogen and carbon sources in desert ecosystems, cyanobacteria can, to a certain extent, increase the content of soil organic matter and improve the soil microenvironment during the processes of photosynthesis and nitrogen fixation. At the same time, cyanobacteria can also form microbial populations with other microorganisms in the soil, increasing the quantity and activity of soil enzymes on the soil surface, thereby accelerating the process of soil development and maturation. In arid desert areas, due to characteristics such as lack of organic matter and loose granular structure, this area is extremely vulnerable to erosion. Cyanobacteria, especially the extracellular polysaccharide substances secreted by them, play an important role in preventing soil surface erosion. Relevant research results show that cyanobacteria improve the soil surface aggregation force and soil particle stability, which is largely determined by the biomass of cyanobacteria and the yield of polysaccharides

[26] . Cyanobacteria produce extracellular polysaccharides, which enhance the stability of the soil and other non-mycelial substances, and at the same time play a mediating role between filamentous cyanobacteria and soil gravel, acting as a basic framework and binding the upper and lower layers of soil. As the number and biomass of cyanobacteria continue to increase, the content of polysaccharides also continues to increase, thus continuously enhancing the aggregation effect of soil particles. In addition, polysaccharides can regulate the absorption and loss of cell water, providing a natural barrier for cyanobacterial cells to protect them from damage, and also reducing or delaying water loss in the biological soil crust layer, thereby increasing the water holding capacity of the soil and laying a solid foundation for the improvement of the microenvironment. These functions are of great significance for the colonization of cyanobacterial groups in oligotrophic tropical coral island areas.

[0004] Although cyanobacteria contain bacteriochlorophyll and can produce extracellular polysaccharides, there are currently no relevant research reports on cyanobacteria reducing soil and water loss in coral islands and promoting the growth of biological soil crusts. Summary of the Invention

[0005] The purpose of the present invention is to provide a cyanobacterial strain Oculatella sp. SCSIO17256 with high extracellular polysaccharide production, isolated from biological soil crust samples in tropical coral islands of China, so as to provide new microbial resources for reducing soil and water loss in coral islands and promoting the development of biological soil crusts in coral islands.

[0006] The cyanobacterial strain Oculatella sp. SCSIO17256 of the present invention was deposited at the China Center for Type Culture Collection (CCTCC) on March 18, 2025. Address: Wuhan University, Wuhan, China, Postcode: 430072, Deposit Number: CCTCC NO: M2025524.

[0007] According to the Phenol-Sulphuric Acid Method, the extracellular polysaccharide content of strain SCSIO17256 was determined using a glucose standard curve. The results showed that its extracellular polysaccharide production was 595.23 mg / L. When the BG11 liquid culture of the cyanobacterium Oculatella sp. SCSIO17256 was evenly sprayed on sterile coral sand with a particle size less than 1.25 mm, after 120 days of cultivation, it was found that it could effectively promote the formation of soil aggregates and form a crust structure on the surface of calcareous sand. The shear strength was measured, and the result was 5.25 ± 0.61 KPa, significantly higher than 1.75 ± 0.11 KPa of the blank group, indicating that the cyanobacterium Oculatella sp. SCSIO17256 can effectively reduce the erosion of calcareous sand and contribute to the prevention and control of soil and water loss on coral islands with calcareous sand.

[0008] The second object of the present invention is to provide a biological preparation, which contains the cyanobacterium Oculatella sp. SCSIO17256. Preferably, the biological preparation further contains excipients that can extend the active time of the strain, or other excipients acceptable for biological preparations.

[0009] The third object of the present invention is to provide the application of the cyanobacterium Oculatella sp. SCSIO17256 or a biological preparation containing this strain in preventing soil and water loss. Preferably, the desertification control includes reducing soil and water loss on coral islands.

[0010] Preferably, the cyanobacterium Oculatella sp. SCSIO17256 promotes the formation of biological soil crust on the surface of calcareous sand, playing a role in stabilizing sand and conserving water, thereby reducing soil and water loss.

[0011] Preferably, the bacterial liquid of the cyanobacterium Oculatella sp. SCSIO17256 is inoculated into the area where biological soil crust needs to be cultivated. The bacterial liquid is obtained by culturing the cyanobacterium Oculatella sp. SCSIO17256 strain using BG11 liquid medium. The formula of the BG11 liquid medium is: NaNO3 (1.5 g / L), K2HPO4 (40 mg / L), MgSO4·7H2O (75 mg / L), CaCl2·2H2O (36 mg / L), Na2CO3 (20 mg / L), Citric Acid (6 mg / L), Ferric ammonium citrate (6 mg / L), EDTA (1 mg / L), A5 trace elements 1 ml / L.

[0012] The fourth object of the present invention is to provide a method for sand fixation, comprising the following steps: inoculating the bacterial solution of cyanobacterium Oculatella sp. SCSIO17256 into the area where biological soil crust needs to be cultivated.

[0013] The fifth object of the present invention is to provide the application of the above-mentioned sand fixation method in the prevention and control of soil and water loss on islands and reefs.

[0014] The extracellular polysaccharide content of the cyanobacterium Oculatella sp. SCSIO17256 provided by the present invention is 595.23 mg / L, which has strong anti-erosion ability, can effectively promote the accumulation of nutrients and prevent soil erosion on coral islands, and can be applied to reduce soil and water loss on coral islands and the construction of biological crusts on coral islands. The present invention discloses for the first time the qualitative and quantitative research on the ability of cyanobacterium Oculatellasp. SCSIO17256 to promote the growth of biological crusts.

[0015] Oculatella sp. SCSIO17256 was deposited on March 18, 2025 at the China Center for Type Culture Collection (CCTCC), address: Wuhan University, Wuhan, China, 430072, deposit number: CCTCC NO: M2025524. Description of the Drawings

[0016] Figure 1 It is the effect diagram of different periods of the crust formed by cyanobacterium Oculatella sp. SCSIO17256 on the surface of calcareous sand. Detailed Embodiments

[0017] The following embodiments are further descriptions of the present invention rather than limitations on the present invention.

[0018] Example 1: Isolation and Identification of Cyanobacterium Oculatella sp. SCSIO17256

[0019] 1. Sample Collection

[0020] The biological crust sample was collected from a tropical coral island in China in December 2021. After the sample was collected, it was quickly put into a sterile polyethylene sampling bag, air-dried, and stored at room temperature.

[0021] 2. Isolation Medium

[0022] The cyanobacteria medium is BG-11 medium, and its formula is: NaNO3 (1.5 g / L), K2HPO4 (40 mg / L), MgSO4·7H2O (75 mg / L), CaCl2·2H2O (36 mg / L), Na2CO3 (20 mg / L), Citric Acid (6 mg / L), Ferric ammonium citrate (6 mg / L), EDTA (1 mg / L), A5 trace elements 1 ml / L. It can be obtained after sterilization and disinfection.

[0023] 3. Isolation and screening of strains

[0024] The biological crust samples brought back to the laboratory are washed with sterile pure water to separate the thalli from the sand and soil. They are inoculated into the sterile cyanobacteria medium at a ratio of 1:5 and enriched for 3 - 5 days under the conditions of a light intensity of 200 μmol photons m -2 s -1 , and a temperature of 20 ± 1 °C. After the water sample shows a visible color to the naked eye, the pre-cultured culture is separated and purified using the dilution coating method or the streaking method on a solid plate under sterile conditions. The plate is placed on a light culture rack under the above conditions for 7 - 15 days. The above separation steps are repeated multiple times until the completely sterile target cyanobacteria single colony SCSIO17256 is obtained.

[0025] Single colony SCSIO17256 is picked from the solid plate and transferred to a triangular flask containing 20 mL of sterilized seawater medium, and continuously illuminated and cultured on a light culture rack, with regular shaking of the flask to obtain cyanobacteria SCSIO17256 in the logarithmic phase. The genomic DNA of strain SCSIO17256 is extracted using EasyPure Bacteria Genomic DNA Kit (TransGen Biotech), and then the 16S rRNA gene fragment is amplified and sequenced using the universal primers 27F / 1492R. Its sequence is shown as SEQ ID No.1. By online alignment of the 16S rRNA gene sequence through the EZBioCloud website, it is found that strain SCSIO17256 belongs to the genus Oculatella of Cyanophyta, so it is named Oculatella sp. SCSIO17256. Cyanobacteria Oculatella sp. SCSIO17256 was deposited at the China Center for Type Culture Collection (CCTCC) on March 18, 2025. Address: Wuhan University, Wuhan, China, Zip Code: 430072, Deposit Number: CCTCC NO: M2025524.

[0026]

[0027] Example 2: Determination of the extracellular polysaccharide content of the cyanobacterium Oculatella sp. SCSIO17256

[0028] The cyanobacterium SCSIO17256 was inoculated into BG11 liquid medium, and the medium components were: NaNO3 (1.5 g / L), K2HPO4 (40 mg / L), MgSO4·7H2O (75 mg / L), CaCl2·2H2O (36 mg / L), Na2CO3 (20 mg / L), Citric Acid (6 mg / L), Ferric ammonium citrate (6 mg / L), EDTA (1 mg / L), A5 trace elements 1 ml / L, and it was obtained by sterilization. It was cultured for 30 days at 25 °C and 180 r / min. Take 2 ml of the cyanobacterium culture solution (cultured for 15 d), centrifuge at 5000 rpm for 5 min to obtain the supernatant. Take 1 ml of the supernatant, add 0.5 ml of 6% phenol solution (prepared freshly before use), then add 2.5 ml of concentrated sulfuric acid, shake well and water bath at 60 °C for 30 min. After cooling to room temperature, measure the absorbance value at a wavelength of 490 nm. With the reagent blank as the reference and D-glucose as the standard, the extracellular polysaccharide content was obtained through the standard curve. The detection results showed that when the cyanobacterium Oculatella sp. SCSIO17256 was cultured in BG11 liquid medium for 30 days, its extracellular polysaccharide yield was 595.23 mg / L.

[0029] Example 3: Determination of the shear resistance of the cyanobacterium Oculatella sp. SCSIO17256

[0030] The coral sand was screened through a 16-mesh sieve (sieve hole 1.25 mm) to obtain coral sand with a particle size less than 1.25 mm, which was placed in a petri dish. It was sterilized at 121 °C for 25 min, then placed in an oven at 60 °C and dried until loose and uniform. The cyanobacterium Oculatella sp. SCSIO17256 was inoculated into the BG11 liquid medium (the same as in Example 2). After shaking culture at 25 °C and 180 r / min for 120 days, the bacterial solution was filled into a sterile small sprayer soaked in alcohol and evenly sprayed on the coral sand, with the sterilized BG11 liquid medium as the blank control. After culturing at room temperature for 120 days, the shear resistance of the biological crust formed on the surface was measured. The test results showed that the cyanobacterium Oculatella sp. SCSIO17256 could effectively promote the formation of biological crust, and the shear resistance was 5.25 ± 0.61 KPa, which was significantly higher than that of the blank group (1.75 ± 0.11 KPa). This indicated that the cyanobacterium Oculatella sp. SCSIO17256 was helpful for the formation of biological crust and could effectively reduce the impact of soil erosion.

[0031] Therefore, it can be seen that the cyanobacterium Oculatella sp. SCSIO17256 provided by the present invention can effectively promote the formation of biological crust on calcareous sand ( Figure 1 ), has strong sand-fixing ability, and extremely strong shear resistance, and can be applied to the prevention and control of soil and water loss on coral islands and the construction of biological soil crust on calcareous sand of coral islands. Compared with physical sand-fixing, chemical sand-fixing, and vegetation cultivation, using microorganisms as a new method for sand-fixing and cultivating crust has the advantages of strong adaptability, low cost, and quick effect.

[0032] The above is only the preferred embodiment of the present invention. It should be noted that the above preferred embodiment should not be regarded as a limitation of the present invention. The protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art in this technical field, without departing from the spirit and scope of the present invention, several improvements and refinements can also be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Cyanobacterium Oculatella sp. SCSIO17256, preservation number: CCTCC NO: M2025524.

2. A biological agent, characterized in that, Comprising the cyanobacterium Oculatella sp. SCSIO17256 described in claim 1.

3. The biological agent according to claim 2, characterized in that, The said biological agent further comprises an adjuvant capable of prolonging the active time of the strain, or other adjuvants acceptable to other biological agents.

4. Application of the cyanobacterium Oculatella sp. SCSIO17256 or a biological agent containing this strain in preventing soil and water loss.

5. The application according to claim 4, characterized in that, The said prevention of soil and water loss includes reducing soil and water loss on coral islands.

6. The application according to claim 4, characterized in that It is that the cyanobacterium Oculatella sp. SCSIO17256 promotes the formation of biological soil crust on the surface of calcareous sand, playing a role in stabilizing sand and retaining water, thereby reducing soil and water loss.

7. The application according to claim 4, wherein it is Inoculating the bacterial liquid of the cyanobacterium Oculatella sp. SCSIO17256 into the area where biological soil crust needs to be cultivated.

8. The application according to claim 7, characterized in that, The said bacterial liquid is obtained by culturing the cyanobacterium Oculatella sp. SCSIO17256 strain using BG11 liquid medium, and the formula of the said BG11 liquid medium is: NaNO3 1.5 g / L, K2HPO4 40 mg / L, MgSO4·7H2O 75 mg / L, CaCl2·2H2O 36 mg / L, Na2CO3 20 mg / L, citric acid 6 mg / L, ammonium ferric citrate 6 mg / L, EDTA 1 mg / L, A5 trace elements 1 ml / L.

9. A method for sand fixation, characterized in that, Inoculating the bacterial liquid of the cyanobacterium Oculatella sp. SCSIO17256 described in claim 1 into the area where biological soil crust needs to be cultivated.

10. Application of the sand fixation method described in claim 9 in preventing soil and water loss on reef islands.

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