Trichomonas vaginalis S1-158 and its applications

Abstract

This invention discloses *Comamonas* sp. strain S1-158 and its applications. Strain S1-158 is a new species of *Comamonas* sp. capable of efficiently synthesizing volatile selenium, with accession number GDMCC No: 63731. The *Comamonas* sp. strain S1-158 of this invention exhibits strong tolerance to selenate, selenite, and elemental selenium, and can efficiently convert selenite and elemental selenium into volatile selenium. A method for the large-scale preparation of methylselenic acid using a bioreactor has also been established, which can be used for the treatment of selenium-containing wastewater and the bioremediation of selenium-polluted environments, showing broad application prospects.

Description

Technical Field

[0001] This invention relates to the fields of microbiology and selenium-contaminated environmental remediation technology, specifically to a strain of Trichomonas vaginalis S1-158 and its applications. Background Technology

[0002] Selenium (Se), an essential trace element for humans and animals, is crucial for maintaining various physiological functions. However, there is a very narrow boundary between the bioavailability and toxicity of selenium, making excessive selenium intake a potential risk of selenium poisoning. Environmental selenium pollution poses a significant threat to ecosystems and human health. Industrial activities, particularly coal and phosphate mining, metallurgy, and the production and processing of selenium products, are the main sources of environmental selenium pollution. The direct discharge of selenium-containing wastewater from industrial activities into the environment without treatment will exacerbate this problem. Currently, the main methods for treating selenium-polluted wastewater are chemical flocculation and biological reduction. Chemical flocculation removes selenates (Se(VI)) and selenites (Se(IV)) by co-precipitating selenium oxides with zero-valent iron and iron salts, but it produces selenium-containing chemical sludge that is difficult to treat. The biological reduction method uses microorganisms to reduce selenium oxides to low-toxicity elemental selenium. However, the generated elemental selenium mostly exists in the form of colloidal selenium nanoparticles (SeNPs), which are difficult to settle in water and are toxic to aquatic organisms. Furthermore, the precipitated SeNPs form new sources of selenium pollution in sludge, requiring secondary treatment.

[0003] Recent studies have discovered that certain microorganisms can convert selenium compounds such as selenites and selenates into volatile organic selenium, such as dimethylselenoseleno(DMSe), dimethyldiselenoseleno(DMDSe), and dimethylselenosulfur(DMSeS), through a methylation process, thereby transferring selenium from soil and aquatic environments to the atmosphere. Currently reported selenium-volatile microorganisms include *Escherichia coli*, *Staphylococcus aureus*, *Bacillus sp. LHVE*, *Pseudomonas stutzeri NT-1*, *Pseudomonas tolaasii*, and *Stenotrophomonas bentonitica*. CN115975881A discloses a new species of selenium-volatile achromobacterium (*Achromobacter eleniivolatilans*) that can convert selenium compounds in wastewater into volatile selenium and recover it as methylselenic acid through a tail gas capture device, providing a new approach for the environmental remediation and resource utilization of selenium pollution. However, compared with elemental selenium-synthesizing bacteria, the number and types of selenium-volatile bacteria that have been discovered so far are relatively small.

[0004] The genus *Comamonas* belongs to the family Comamonadaceae and the order Burkholderiales, and currently comprises 28 formally published species. Among them, the aerobic bacterium *Comamonas testosteroni* S44 exhibits tolerance to 100 mM Se(IV) and can reduce Se(VI) and Se(IV) to selenium nanoparticles with a size of 100–200 nm. Related studies have revealed its selenium reduction mechanism and nano-selenium stabilization mechanism (Tan et al., 2018; Xu et al., 2018). Despite the significant potential of *Comamonas* in selenium reduction, there are currently no reports on the synthesis of volatile selenium by microorganisms within this genus. This invention aims to provide a new species of Trichomonas vaginalis with selenium volatility. By utilizing the biomethylation pathway of this strain, selenium compounds such as Se(IV) and SeNPs can be converted into volatile selenium. This not only enables the effective treatment of selenium-polluted wastewater and promotes the recycling of selenium resources, but also provides a new strategy for the development of the anticancer drug methylselenic acid. Summary of the Invention

[0005] The purpose of this invention is to provide a new strain of Trichomonas vaginalis, S1-158, capable of efficiently synthesizing volatile selenium, and its application in the remediation of selenium-contaminated environments and the preparation of methylselenic acid.

[0006] To achieve the objectives of this invention, in a first aspect, this invention provides a strain of *Comamonas* sp. isolated and purified from soil, classified as *Comamonas* sp., which is now deposited at the Guangdong Provincial Microbial Culture Collection Center (GDMCC), located at: 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, Guangdong Province, 510070, China (Institute of Microbiology, Guangdong Academy of Sciences, Guangdong Province, China), accession number GDMCC No: 63731, deposit date August 11, 2023.

[0007] Secondly, this invention provides the application of Trichomonas vaginalis S1-158 in the remediation of selenium-contaminated environments and the preparation of methylselenic acid.

[0008] Thirdly, the present invention provides a method for the biosynthesis of nano-selenium, wherein *Trichoderma spp.* S1-158 is inoculated into a culture medium containing sodium selenite and / or sodium selenate, and after being cultured for a period of time, nano-selenium is isolated and purified from the culture medium.

[0009] Furthermore, in the culture medium containing sodium selenite and / or sodium selenate, the initial sodium selenate concentration is 100–200 mM, the initial sodium selenite concentration is 1–20 mM, and preferably the initial selenium concentration is 5 mM sodium selenite.

[0010] Fourthly, the present invention provides a method for synthesizing volatile selenium, wherein Trichomonas vaginalis S1-158 is inoculated into a culture medium containing sodium selenite and / or nano-selenium, and after being cultured for a period of time, the generated volatile selenium is collected.

[0011] The volatile selenium includes, but is not limited to, dimethyldisiselenide, dimethylselenone, triselenothane, and dimethylselenosulfide. Dimethyldisiselenide and dimethylselenone are the most common.

[0012] Furthermore, in the culture medium containing sodium selenite and / or nano-selenium, the initial selenium concentration is 10-400 mg / L, preferably 10, 20 or 40 mg / L.

[0013] Furthermore, the culture medium can be LB or TSB medium.

[0014] Furthermore, the cultivation conditions were: 28℃ and 150 rpm.

[0015] Fifthly, the present invention provides the application of the method in the preparation of methylselenic acid.

[0016] The volatile selenium produced according to the method is passed into a capture solution containing an oxidant, so that the volatile selenium (such as dimethyldiselement, dimethylselenophenone) is oxidized to water-soluble methylselenic acid.

[0017] Furthermore, the oxidizing agent includes, but is not limited to, nitric acid or hydrogen peroxide.

[0018] By employing the above technical solution, the present invention has at least the following advantages and beneficial effects:

[0019] The *Comamonas* sp. S1-158 strain of this invention exhibits strong tolerance to selenate, selenite, and elemental selenium, and can efficiently convert selenite and elemental selenium into volatile selenium. A method for preparing methyl selenic acid using a bioreactor has also been established, which can be used for the treatment of selenium-containing wastewater and the bioremediation of selenium-polluted environments, showing broad application prospects. Attached Figure Description

[0020] Figure 1 The colony (a) and cell (b) morphological characteristics of strain S1-158 in a preferred embodiment of the present invention are shown.

[0021] Figure 2This is a phylogenetic tree of the 16S rRNA gene of strain S1-158 in a preferred embodiment of the present invention. The phylogenetic tree was constructed using the maximum likelihood method, with Kiruma's 2-parameter model. The numbers at the branches represent 1000 bootstrap values. The figure shows bootstrap values ​​greater than 50%, and the GenBank accession number of the strain's 16S rRNA gene sequence is in parentheses. The scale bar represents the 1% nucleotide substitution rate. Note: In 2023, Acidovorax antarcticus was renamed Commonasantarctica (Du et al. 2023).

[0022] Figure 3 This is a phylogenetic tree of the whole genome and core genes of strain S1-158 in a preferred embodiment of the present invention. a) is a phylogenetic tree based on the whole genome constructed using the TYGS tool. Branch lengths are calculated according to the GBDP evolutionary distance formula d5. The displayed branch values ​​are from 100 GBDP pseudo-bootstrap values, with an average branch support rate of 84.8%. The scale bar represents 2% nucleotide difference. b) is a phylogenetic tree based on 92 single-copy core genes constructed using the UBCG tool. The data at the nodes represent the Gene Support Index (GSI), and the scale bar represents 10% nucleotide difference.

[0023] Figure 4 The preferred embodiment of the present invention demonstrates the tolerance and reducing ability of strain S1-158 to sodium selenate and sodium selenite.

[0024] Figure 5 The following are characteristics of the synthesis of selenium nanoparticles by strain S1-158 through the reduction of sodium selenite in a preferred embodiment of the present invention. a is a TEM image of the selenium nanoparticles synthesized by the strain through the reduction of 5 mM Se(IV), b is a photograph of the purified selenium nanoparticles, c is the EDS spectrum of the selenium nanoparticles indicated by the arrow in the TEM image, and d is the Raman spectrum of the selenium nanoparticles.

[0025] Figure 6 The volatilization efficiency of strain S1-158 for Se(IV) and SeNPs in a preferred embodiment of the present invention.

[0026] Figure 7This is a GC-MS analysis of the synthesis of volatile selenium by strain S1-158 in a preferred embodiment of the present invention. The peaks in the figure indicate volatile selenium and volatile sulfur compounds: 1-dimethyldisulfide, 2-dimethylselenone, 3-dimethyldiselenide, 4-dimethylselenyl sulfide, and 5-triselenothane. Detailed Implementation

[0027] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention. Unless otherwise specified, the examples are conducted under conventional experimental conditions, such as those described in Sambrook et al.'s Molecular Cloning: A Laboratory Manual (Sambrook J & Russell DW, Molecular Cloning: A Laboratory Manual, 2001), or as recommended by the manufacturer's instructions.

[0028] Example 1: Isolation and Identification of Trichomonas vaginalis S1-158

[0029] 1. Strain Isolation: Rhizosphere soil was collected from around *Capsella bursa-pastoris*, a selenium hyperaccumulator, in the Yutangba area of ​​Enshi, Hubei Province. 5g of soil was added to 95mL of sterile physiological saline, and the mixture was shaken at 25℃ and 150rpm for 30min. After a 10-fold serial dilution, 100μL of the diluted soil was plated onto NA plates supplemented with 10mM sodium selenite and incubated at 28℃ for 2 days to obtain sodium selenite-tolerant strains. These strains were then purified by streaking. A Gram-negative bacterium, S1-158, capable of synthesizing volatile selenium, was isolated from these strains.

[0030] 2. Colony and cell morphology analysis: Strain S1-158 was Gram-negative. After incubation on TSA medium at 28°C for 2 days, the colonies were round, 1–2 mm in diameter, with a moist and glossy surface, neat edges, and no pigment production. Figure 1 a). TEM observations revealed that the bacteria were rod-shaped, 1.7–2.5 μm long and 1.0–1.5 μm wide, and possessed flagella ( Figure 1 b). It is motile and produces a swimming coil on a semi-solid culture medium.

[0031] 3. Phylogenetic analysis of the 16S rRNA gene: Genomic DNA was extracted from strain S1-158 using a bacterial DNA extraction kit, and its 16S rRNA gene was amplified using universal primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3') and 1492R (5'-GGTTACCTTGTTACGACTT-3'). The PCR products were purified and sequenced, and the sequencing results were assembled using DNAMAN software (SEQ ID NO:1). The 16S rRNA gene similarity was compared using the EzBioCloud analysis platform (www.ezbiocloud.net / ). The results showed that strain S1-158 had the highest similarity to strains of the genera *Acidovorax*, *Comamonas*, and *Delftia*, with *Comamonas santarctica* 16-35-5 showing the highest similarity. T The similarity was highest at 98.87%, while the similarity with the other strains was all below 98.7%.

[0032] A phylogenetic tree of 16S rRNA genes of strain S1-158 and closely related genera was constructed using MEGA software. The results showed that strain S1-158 and *Comamonas antarctica* 16-35-5... T , Comamonas granuli NBRC 101663 T And multiple Acidovorax spp. clustered in one branch ( Figure 2 However, the 16S rRNA gene alone is insufficient to effectively distinguish strains of the genera *Acidovorax*, *Delftia*, and *Comamonas*, requiring further analysis of the genome sequence.

[0033] 4. Genome sequencing and genome similarity analysis: The whole genome of strain S1-158 was sequenced using the Illumina NovaSeq platform, and the genome size was determined to be 6.39 Mb with a G+C content of 65.0 mol% (Table 1). Genome-based species identification results conducted using the Model (Strain) Genome Server (TYGS, https: / / tygs.dsmz.de) showed that strain S1-158 belongs to a potential new species. The average nucleotide similarity (ANI) of strain S1-158 with closely related bacteria such as *Acidovorax*, *Comamonas*, and *Delftia* was calculated using JSpeciesWS (https: / / jspecies.ribohost.com / jspeciesws / #analyse). The digital DNA-DNA hybridization (dDDH) value was calculated using GGDC Calculator 3.0 (http: / / ggdc.dsmz.de). The results showed that strain S1-158 is similar to *Comamonas santarctica* 16-35-5. T and Comamonas endophytica 5MLIR T The genome similarity was the highest, with ANI values ​​of 85.1% and 84.6%, and dDDH values ​​of 30.3% and 29.5%, respectively (Table 2), all of which were below the species threshold (ANI = 95-96%, dDDH = 70%), indicating that S1-158 is a new species of the genus Commamonas.

[0034] Table 1. Sequence information used in genomic analysis and ANI and dDDH values ​​of strain S1-158 and closely related bacteria.

[0035]

[0036] 5. Genome phylogenetic analysis: The whole genome phylogenetic tree constructed using TYGS showed that strain S1-158 is related to Commonas antarctica 16-35-5. T and Comamonas endophytica 5MLIR T Gathered in a small branch ( Figure 3a). Using the UBCG tool (www.ezbiocloud.net / tools / ubcg), 92 common single-copy core genes were extracted from the genome, and a tandem sequence phylogenetic tree was constructed. This also showed that strain S1-158 belongs to the genus *Comamonas*, and is related to *Comamonas santarctica* 16-35-5. T and Comamonas endophytica 5MLIR T The closest kinship ( Figure 3 b).

[0037] 6. Stress resistance experiment of strain S1-158

[0038] Strain S1-158 was inoculated onto TSA plates and cultured at 4, 10, 20, 28, 30, 32, 34, 37, 40, and 42℃ for 4 days, respectively, and the growth of the strain was observed. Salt-containing media were prepared by adding 1, 2, 3, 4, 5, 6, 7, and 8% (w / v) NaCl to TSB medium, respectively. After inoculation with strain S1-158, the media were cultured at 28℃ and 150 rpm for 4 days, and the growth was observed. The pH of the TSB culture medium was adjusted to 4, 5, 6, 7, 8, 9, 10, and 11 with HCl (6M) and NaOH (2M), respectively. After inoculation with strain S1-158, the media were cultured at 28℃ and 150 rpm for 4 days, and the growth was observed. The results showed that strain S1-158 had higher stress resistance than closely related bacteria, with a growth temperature range of 4-37℃ and a growth pH range of 6-11, and could tolerate 5% NaCl (Table 2).

[0039] 7. Physiological and Biochemical Indicators: Strain S1-158 exhibits facultative anaerobic growth, is positive for oxidase and catalase, and negative for hemolysis. API 20NE identification results show that strain S1-158 is negative for nitrate reduction, arginine dihydrolase, urease, and β-galactosidase; it does not synthesize indole, hydrolyze esculin or gelatin, or ferment glucose; it can utilize gluconate, adipic acid, and malic acid, but not glucose (D-glucose), arabinose (L-arabinose), mannose, mannitol, N-acetyl-β-glucosamine, maltose, capric acid, citric acid, or phenylacetic acid. API ZYM identification results showed that C4 esterase, C8 lipoesterase, leucine aminopeptidase, acid phosphatase, and naphthol-AS-Bl-phosphatase were positive.

[0040] In addition, it is related to the closely related bacterium Commonas antarctica 16-35-5 T and Commonas endophytica 5MLIR T In comparison, strain S1-158 differed in the following indicators: growth temperature and pH range, salt tolerance, nitrate reduction, utilization of carbon sources such as glucose, gluconate, adipic acid, and malic acid, and alkaline phosphatase activity (Table 2).

[0041] Table 2. Differential physiological and biochemical characteristics of strain S1-158 and closely related species.

[0042]

[0043] Based on the above 16S rRNA gene and genomic phylogenetic analysis, as well as morphological characteristics and physiological and biochemical properties, strain S1-158 was identified as a new species of the genus Commamonas and is now deposited at the Guangdong Provincial Microbial Culture Collection Center (GDMCC) with accession number GDMCC No: 63731.

[0044] Example 2: Tolerance and reduction of selenate and selenite by strain S1-158

[0045] Prepare TSA solid medium (BD Bacto). When cooled to approximately 60°C, add filtered and sterilized sodium selenate and sodium selenite solutions separately. Gently shake to mix, then pour the mixture onto a plate to prepare selenium-containing plates containing 0–200 mM sodium selenate and 0–100 mM sodium selenite. Pick a single colony of strain S1-158 and inoculate it into TSB tubes (BD Bacto). Activate the culture by incubating at 28°C and 150 rpm for 12 hours, adjusting the OD of the bacterial culture. 600 The concentration was 0.8, which was used as the seed culture. After being serially diluted 10-fold with sterile physiological saline, 2.5 μL of each gradient was added to a selenium-containing plate. After being dried with sterile air, the plate was incubated at 28°C for 4 days to observe the growth of the strain.

[0046] See results Figure 4 Growth on selenium-containing plates showed that S1-158 could tolerate at least 200 mM selenate and 20 mM selenite, and the colonies on the selenite plate were bright red, indicating the production of red elemental selenium. On the selenate plate, the colonies only synthesized red elemental selenium at high concentrations (100–200 mM). Figure 4 ).

[0047] Example 3: Characteristic Analysis of Selenium Synthesis by Strain S1-158

[0048] Single colonies of S1-158 were picked and inoculated into LB tubes (yeast extract 5 g / L, tryptone 10 g / L, sodium chloride 10 g / L, pH 7.0–7.2, sterilized at 121℃ for 20 min), and activated by shaking at 28℃ and 150 rpm for 12 h. The OD of the bacterial culture was then adjusted. 600 The initial concentration of sodium selenite was 0.8, and 1% was inoculated into LB shake flasks. The corresponding volumes of sodium selenite and sodium selenate stock solution (filtered and sterilized) were added to make the initial sodium selenite concentration 1–5 mM or sodium selenate concentration 100–200 mM. The flasks were incubated at 28°C and 150 rpm for 2 days. The morphology of elemental selenium synthesized by strain S1-158 was observed by transmission electron microscopy (TEM). The elemental composition of elemental selenium was analyzed by energy dispersive X-ray spectroscopy (EDS). After extraction and purification, the crystal form of elemental selenium was analyzed by Raman spectroscopy.

[0049] The results showed that the elemental selenium synthesized by strain S1-158 through the reduction of Se(IV) and Se(VI) was in the form of spherical nanoparticles. TEM images of the 5 mM sodium selenite-treated group are shown below. Figure 5 The nano-selenium particles are distributed in the range of 50–600 nm, with an average particle size distribution of 200–300 nm. Figure 5 (a and b). The EDS energy dispersive spectroscopy analysis of the nanoparticles shows characteristic selenium peaks at 1.37 keV, 11.22 keV, and 12.50 keV, indicating that the nanoparticles synthesized by the strain are nano-selenium (a and b). Figure 5 c). Raman spectrum visible at 253 cm⁻¹ -1 The characteristic Raman shift peaks of amorphous elemental selenium indicate that the nano-selenium is amorphous. Figure 5 d).

[0050] Example 4: Volatilization efficiency of strain S1-158 for Se(IV) and SeNPs

[0051] Pick a single colony of S1-158 and inoculate it into an LB tube. Incubate at 28°C and 150 rpm for 12 hours, then adjust the OD of the bacterial culture. 600 The initial concentration was 0.8, used as the seed culture. A 1% inoculum was added to a shake flask containing 50 mL of LB broth (LB broth: yeast extract 5 g / L, tryptone 10 g / L, sodium chloride 10 g / L, pH 7.0-7.2, sterilized at 121℃ for 20 min), and the corresponding volume of sodium selenite or chemically synthesized nano-selenium stock solution (filtered and sterilized) was added to achieve initial selenium concentrations of 10, 20, and 40 mg / L (as Se). The flasks were then incubated at 28℃ with shaking at 150 rpm for 4 days. The reduction in total selenium in the bacterial culture after 4 days of incubation was measured using atomic fluorescence spectrometry (HG-AFS), and the selenium volatilization rate was calculated.

[0052] Selenium volatilization rate (%) = (Selenium added to bacterial solution - Remaining selenium in bacterial solution) / Selenium added to bacterial solution × 100%

[0053] The test results showed that after 4 days of cultivation, the total selenium in the culture medium inoculated with S1-158 decreased significantly, and a strong garlic-like odor was produced during the cultivation process. At a selenium addition of 10 mg / L, the selenium volatilization rates of S1-158 for Se(IV) and SeNPs reached 92.3% and 86.9%, respectively. Figure 6 The strain exhibited the highest volatilization of SeNPs at a concentration of 20 mg / L, reaching 15.4 mg (per liter of culture medium), while the highest volatilization of Se(IV) was observed at a concentration of 40 mg / L, reaching 23.4 mg (per liter of culture medium). Figure 6 ).

[0054] Example 5: Identification of volatile selenium synthesized by strain S1-158

[0055] LB medium was added to headspace vials, followed by the addition of 40 mg / L of Se(IV) and SeNPs, respectively. After inoculation with S1-158 seed culture and cultured for 4 days, the top gas was analyzed using GC-MS to identify the volatile selenium species. The results showed that the volatile selenium species synthesized from the conversion of Se(IV) and SeNPs by S1-158 included dimethyldisiselenide, dimethylselenone, dimethyl selenyl sulfide, and triselenothane. It also synthesized the volatile sulfur compound dimethyldisulfide. Figure 7 Of these, dimethyldiselenoside and dimethylselenophenone had the highest abundance. Figure 7 ).

[0056] Methylation is a key detoxification mechanism in organisms. Selenium methylation helps reduce the biotoxicity of selenium compounds and prevents excessive selenium from participating in biological activities such as protein synthesis. Furthermore, in the biogeochemical cycle of selenium, microorganisms with selenium volatility convert selenates, selenites, and elemental selenium into volatile selenium compounds through methylation, thereby transferring selenium from soil and water into the atmosphere and preventing it from entering the food chain and food web. This is a crucial link in the biogeochemical cycle of selenium.

[0057] Example 6: Removal of Se(IV) and SeNPs and preparation of methylselenic acid using strain S1-158 in a bioreactor

[0058] Single colonies of strain S1-158 were picked and inoculated into LB test tubes. After activation by shaking at 28℃ and 150 rpm for 12 h, 1% of the culture was inoculated into 70 mL LB shake flasks and cultured at 28℃ and 150 rpm for 8 h to prepare shake flask seed culture. 7 mL of LLB medium was added to a 10 L fermenter and sterilized at 121℃ for 20 min. After the temperature dropped to 28℃, 70 mL of seed culture was inoculated, along with 14 mL of Se(IV) stock solution (10 g / L, as Se) and 14 mL of SeNPs stock solution (10 g / L, as Se), so that the fermentation broth contained 20 mg(Se) / L of Se(IV) and SeNPs, respectively. The tail gas pipeline was connected to a buffer bottle, a gas washing bottle, and a tail gas absorption bottle. Concentrated nitric acid was added to the absorption bottle to capture volatile selenium in the tail gas. The fermentation temperature was controlled at 28 ± 0.5℃, the stirring speed at 150 rpm, and the aeration rate at 210 L / h, and the fermentation time was 24 h. The residual selenium content in the fermentation broth was determined using atomic fluorescence spectrometry (HG-AFS).

[0059] The results showed that with prolonged fermentation time, the cells grew rapidly, dissolved oxygen in the fermentation broth decreased, and pH increased. Se(IV) and SeNPs in the fermentation broth were rapidly converted into volatile selenium and removed from the aqueous phase, with a selenium volatilization rate of 88% after 24 hours. The tail gas capture device recovered 80% of the total selenium, achieving a capture rate of 91% for volatile selenium gas. High-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) was used to identify the selenium species in the capture solution, revealing that methylselenic acid (MSA) was the predominant selenium compound. The study showed that dimethylselenoketone can be oxidized to dimethyldiseleno, and in the nitric acid capture solution, the oxidation product of dimethyldiseleno is MSA, consistent with the GC-MS results.

[0060] MSA is a drug with significant anti-cancer effects. In vivo, it can be converted into methylselenol through the action of reducing agents such as glutathione. methylselenol exhibits selective cytotoxicity against various cancer cells, effectively inhibiting the proliferation of cancer cells such as lung cancer, breast cancer, esophageal cancer, and prostate cancer. Therefore, by cultivating highly efficient selenium-volatile bacteria, such as S1-158, on a large scale in a bioreactor, its biotransformation process can convert selenium compounds such as selenates, selenites, and elemental selenium into volatile selenium, such as dimethyldiselenate and dimethylselenophenone. Furthermore, by adding oxidants such as nitric acid or hydrogen peroxide as a capture liquid in the exhaust gas treatment device, dimethyldiselenate and dimethylselenophenone are oxidized into water-soluble methylselenic acid. This technology not only contributes to the bioremediation of selenium-polluted environments but also provides a new approach to the production of methylselenic acid, showing significant application potential in the environmental and pharmaceutical fields.

[0061] Example 7: Using strain S1-158 to reduce selenium accumulation in plants in high-selenium soil.

[0062] In high-selenium soils, by applying bacterial agent of strain S1-158, the strain converts Se(VI) and Se(IV) in the soil into nano-selenium and / or volatile selenium through bioreduction and methylation processes. This reduces the accumulation of selenium in plants, improves the plant's tolerance to high-selenium environments, reduces the selenium content entering the food chain, and lowers the risk of selenium poisoning in humans and animals in high-selenium areas.

[0063] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. Trichomonas vaginalis Comamonas sp. S1-158, accession number GDMCC No: 63731.

2. The use of the Comamonas sp. of claim 1 in the remediation of selenium-contaminated environments and the production of methylselenic acid.

3. A method for nanoselenium biosynthesis, characterized by, The Comamonas sp. of claim 1 is inoculated into a culture medium supplemented with sodium selenite and / or sodium selenate, and after a period of cultivation, nano-selenium is isolated and purified from the culture broth.

4. The method of claim 3, wherein, In the culture medium supplemented with sodium selenite and / or sodium selenate, the initial sodium selenate concentration is 100-200 mM, and the initial sodium selenite concentration is 1-20 mM.

5. The method of claim 4, wherein, The initial selenium concentration is 5 mM sodium selenite.

6. Process for the synthesis of volatile selenium characterized in that, The Comamonas sp. of claim 1 is inoculated into a culture medium supplemented with sodium selenite and / or nano-selenium, and after a period of cultivation, the volatile selenium produced is collected.

7. The method of claim 6, wherein, In the culture medium supplemented with sodium selenite and / or nano-selenium, the initial selenium concentration is 10-400 mg / L.

8. The method of claim 7, wherein, The initial selenium concentration is 10, 20, or 40 mg / L.

9. The method according to any one of claims 3-8, characterized in that, The culture medium is LB or TSB medium. The culture conditions are 28°C and 150 rpm.

10. The use of the method of any one of claims 6-9 in the production of methylselenic acid.

11. Use according to claim 10, characterized in that, The volatile selenium produced according to the method of any one of claims 6-9 is passed into a capture solution containing an oxidizing agent, so that the volatile selenium is oxidized to water-soluble methylselenic acid.

12. Use according to claim 11, characterized in that, The oxidizing agent comprises nitric acid or hydrogen peroxide.

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