Cryophage and application thereof

Abstract

The invention relates to the field of microorganisms, in particular to a South China Sea-sourced psychrophilus sp. CM16 strain and application of the South China Sea-sourced psychrophilus sp. CM16 strain in reduction of hexavalent chromium into trivalent chromium. The psychrophage disclosed by the invention is classified and named as (Algoxiphagussp), CM16 and preserved in the China Center for Type Culture Collection (CCTCC) on October 23, 2024, the address is Wuhan University, Wuhan, Hubei, China, and the preservation number is CCTCC NO: M 20242309. The invention mainly protects the psychrophilus and a microbial inoculum containing the psychrophilus. The marine-derived psychrophage has the beneficial effects that the marine-derived psychrophage is provided, hexavalent chromium is efficiently converted into non-toxic trivalent chromium under a specific culture condition, so that the toxicity of the marine-derived psychrophage in the environment is remarkably reduced, and the marine-derived psychrophage shows strong adaptive capacity and still has excellent reducing capacity on hexavalent chromium under low-temperature and high-salt conditions.

Description

Technical Field

[0001] The present invention relates to the field of microbial technology, and in particular to a psychrophilic bacterium from the South China Sea. Algoriphagus sp. CM16 and its use in reducing hexavalent chromium to trivalent chromium. Background Art

[0002] Heavy metal pollution has long had a destructive impact on natural ecosystems and has even seriously threatened the health of humans, animals and plants. Take chromium as an example. It occupies an extremely important position in human industrial production and is widely used in many industries such as tanneries, mining, electroplating, pigments, chemicals, steel smelting, textile dyeing, and printing. With the surge in the use of chromium in human industrial production and its continuous release into the environment, chromium pollution has become an extremely common environmental pollution.

[0003] Of the two most common forms of chromium, Cr(III) is non-toxic and is considered one of the essential nutrients for the human body. Cr(VI) is a strong oxidant with strong carcinogenicity, and is listed as a Class A human carcinogen by the EPA and other agencies. Cr(VI) usually enters the human body through the skin, digestive tract, and respiratory tract. After cells absorb Cr(VI), it can interact with biological macromolecules such as DNA, lipids, and proteins to change the expression of related genes. Short-term exposure to Cr(VI) can cause skin irritation such as chromium sores, gastric ulcers, and irregular bowel movements. Long-term exposure to Cr(VI) can induce concentration-dependent aneuploidy and unstable chromosomes.

[0004] In order to cope with the increasing pollution of Cr(VI), many effective measures for Cr(VI) remediation have been developed. Physical methods such as landfill, membrane filtration, soil washing, ultrafiltration, and washing are conventional technologies for Cr(VI) remediation. Chemical treatment methods include ion exchange, advanced oxidation, solvent extraction, precipitation, chemical reduction, and adsorption. However, these physical and chemical methods for Cr(VI) remediation usually produce additional harmful substances, causing secondary pollution. Their high cost and low efficiency also make these methods unsuitable for large-scale promotion and application.

[0005] Existing studies have shown that bacteria-related bioremediation methods are more suitable for treating Cr(VI) pollution. It uses bacteria and other organisms to treat Cr(VI) waste in various ways to achieve treatment effects. Compared with other treatment processes, bioremediation technology has many unique advantages, such as high efficiency, good specificity, low cost, easy large-scale implementation, and high environmental compatibility. A large number of studies have used bacteria isolated from Cr(VI) contaminated sites to verify their Cr(VI) removal effects, which confirms the great potential of bacteria for Cr(VI) bioremediation.

[0006] Most of the Cr(VI)-reducing bacteria found in current research come from land, such as Pseudomonas umsongensis CY-1, Oceanobacillus oncorhynchi W4, etc., while only a few studies have been published on marine bacteria. Marine bacteria have long lived in a high-salt, low-temperature, oligotrophic environment. After a long period of adaptive evolution, they have formed a very unique mechanism of salt resistance, low-temperature resistance, and starvation resistance, and are a rich treasure trove of microbial resources.

[0007] Therefore, relevant research on Cr(VI)-reducing bacteria of marine origin may reveal Cr(VI)-reducing mechanisms that are different from those of terrestrial Cr(VI)-reducing strains, which will be beneficial to expanding the sources of Cr(VI)-reducing bacteria and their related applications under low temperature and high salt conditions, further exploring the application potential of deep-sea microorganisms, meeting the urgent needs for the development of marine natural resources, and providing theoretical guidance for further bioremediation of heavy metal pollution. Summary of the invention

[0008] The purpose of the present invention is to provide a psychrophilic bacterium from the South China Sea Algoriphagus sp. CM16, and also provides the use of the above-mentioned psychrotrophic bacteria in reducing hexavalent chromium to trivalent chromium.

[0009] The psychrophilic bacteria provided by the present invention are classified and named as ( Algoriphagus sp). CM16, deposited in China Center for Type Culture Collection (CCTCC), Wuhan University, Wuhan, Hubei, China, on October 23, 2024, with the deposit number CCTCC NO: M 20242309. The following description of psychrophilic bacteria refers to the strains with the above deposit number.

[0010] The above-mentioned psychrophilic bacteria have strong Cr(VI) reduction ability and can reduce Cr(VI) to Cr(III). According to the measurement, at 25°C and Cr(VI) concentration of 50 mg / L, its chromium reduction efficiency is about 88%. In addition, its tolerance concentration of Cr(VI) is 250 mg / L.

[0011] Experiments have shown that the bacteria have a special Cr(VI) reduction mechanism, which is of great value to the research on the mechanism and application of chromium-reducing bacteria and their industrial application.

[0012] The beneficial effects of the present invention are: (1) The psychrophilic bacteria of the present application ( Algoriphagus sp.) strain CM16 has an excellent ability to remove hexavalent chromium and can efficiently convert hexavalent chromium into non-toxic trivalent chromium under specific culture conditions, thereby significantly reducing its toxicity in the environment; (2) Experimental results in salt solutions of different concentrations showed that CM16 also exhibited strong adaptability to the marine environment, especially under low temperature and high salinity conditions. In this extreme environment, CM16 was still able to efficiently reduce hexavalent chromium to non-toxic trivalent chromium, demonstrating its potential for bioremediation in complex ecosystems.

[0013] In summary, the powerful removal ability of Algoriphagus sp. CM16 for hexavalent chromium provides a feasible bioremediation strategy for heavy metal pollution control and shows important application potential in the field of environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Psychrotrophic bacteria ( Algoriphagus sp.) Scanning electron microscope photo of CM16 (13000 times); Figure 2 Psychrotrophic bacteria ( Algoriphagus sp.) CM16 and some related strains based on 16S rDNA sequence and ANI analysis; Figure 3 Psychrotrophic bacteria ( Algoriphagus sp.) CM16 and some related strains ANI analysis, where T indicates that the selected strain is a model strain; Figure 4 For psychrotrophic bacteria at different temperatures ( Algoriphagus sp.) Growth curve of CM16; Figure 5 For psychrotrophic bacteria at different salinities ( Algoriphagus sp.) Growth curve of CM16; Figure 6 Psychrotrophic bacteria ( Algoriphagus sp.) Cr(VI) reducing ability of CM16; Figure 7 For psychrotrophic bacteria at different salinities ( Algoriphagus sp.) Cr(VI) reducing ability of CM16; Figure 8 Effects of different carbon sources on psychrophilic bacteria ( Algoriphagus sp.) The effect of CM16 Cr(VI) reducing ability; Fig. 9 Different electron acceptors for psychrophilic bacteria ( Algoriphagus sp.) The effect of CM16 Cr(VI) reducing ability; Fig.10 The effects of different heavy metal ions on psychrophilic bacteria ( Algoriphagus sp.) The effect of CM16 Cr(VI) reducing ability; Fig.11Psychrotrophic bacteria ( Algoriphagus sp.) CM16's tolerance concentration to Cr(VI); Fig.12 Psychrotrophic bacteria ( Algoriphagus sp.) CM16 resting cells, heat-treated cells, and spent culture medium for Cr(VI) scavenging; Fig.13 Psychrotrophic bacteria ( Algoriphagus sp.) CM16 permeable cells and the scavenging effects of different cell components on Cr(VI); Fig.14 Psychrotrophic bacteria ( Algoriphagus sp.) Changes in intracellular malondialdehyde (MDA) content in CM16 cells after treatment with different concentrations of Cr(VI); Fig.15 Psychrotrophic bacteria ( Algoriphagus sp.) Changes in intracellular superoxide dismutase (SOD) content in CM16 cells after treatment with different concentrations of Cr(VI); Fig.16 Psychrotrophic bacteria ( Algoriphagus sp.) CM16 cells treated with different concentrations of Cr(VI) and the changes in intracellular catalase (CAT) content. DETAILED DESCRIPTION

[0015] The present invention is further explained below in conjunction with the accompanying drawings and specific examples, but the present invention is not limited thereto. Unless otherwise specified, the following examples are all conventional reagents and method steps in the art.

[0016] Example 1 Psychrotrophic bacteria Algoriphagus Processing of isolated samples of CM16 1.1 Collection Psychrotrophic bacteria Algoriphagus sp. CM16 was isolated from a marine sediment sample collected at a depth of 2446 m in the South China Sea (112°007′E, 18°011′N) in July 2014.

[0017] 1.2 Screening and cultivation The screening process of the above psychrophilic bacteria is as follows: 10 g of sediment sample stored at 4°C (collection see 1.1) was weighed and placed in a 100 mL sterilized artificial seawater conical flask to prepare a sample suspension with a mass fraction of 10%. The suspension was shaken at 180 rpm for 30 min and allowed to stand for 30 s. The suspension was diluted in a gradient manner with dilution multiples of 10, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 29 -1 , 10 -2 , 10 -3 , 10 -4 , 10 -5 , 10-6 , 10 -7 , from dilution factor 10 -5 , 10 -6 , 10 -7 Take 200 μl of the liquid and spread it on the 2216E solid medium plate. Set three replicates for each dilution multiple, and then place it in a 16℃ constant temperature box for static culture. After each colony grows well, repeatedly streak the plate, separate and purify, and finally obtain the strain ( Algoriphagus sp.)CM16.

[0018] Example 2 strain ( Algoriphagus sp.) CM16 biological traits and physiological, biochemical and molecular identification S1 Morphological characteristics strain ( Algoriphagus sp.) The morphology of CM16 under scanning electron microscopy is shown in Figure 1 The colony morphology of the strain after 48 h of culture on 2216E solid medium was: yellow, round, smooth, opaque colonies with a slightly convex center and neat colony edges. Under a scanning electron microscope, CM16 was observed to be a short rod-shaped bacterium, about 8 microns long; Gram staining was negative.

[0019] S2 Psychrotrophic bacteria ( Algoriphagus Sequencing and analysis of 16S rDNA of CM16 Rapid preparation of S21PCR template DNA: Psychrotrophic bacteria ( Algoriphagus sp.) CM16 was streaked on a plate containing 2216E medium (see Example 3 for details) and cultured overnight at 16°C. A single colony was suspended in 10 mL ddH2O, heated in a boiling water bath for 5 min, centrifuged, and the supernatant was used as PCR template DNA.

[0020] S22. 16S rDNA gene PCR amplification PCR primers were synthesized by BGI.

[0021] Primer A (SEQ ID NO: 2): 5′-AGAGTTTGATCCTGGCTCAG-3′; Primer B (SEQ ID NO: 3): 5′-ACGGCTACCTTGTTACGACTT-3′. The PCR reaction system is shown in Table 1: Table 1 PCR reaction system 2 × PCR buffer 2 mmol / L dNTP 25 μL Primer A 2.5 μL Primer B 2.5 μL 5 U / μL Taq DNA Polymerase 1 μM <![CDATA[25 mM MgCl2]]> 1.25 U Template DNA 4 mM Water, nuclease-free 0.5 μg Overall system 50 μL

[0022] PCR amplification conditions: 95°C, 3 min, 95°C, 30 s, 55°C, 1 min, 72°C, 90 s, 30 cycles; 72°C, 10 min.

[0023] Sequence determination: After PCR product purification, it was sent to BGI for sequencing. The sequence was compared with the known sequences in the GenBank database by BLAST analysis, and the 16S rDNA sequences of related species were obtained from the database to construct a phylogenetic tree. Figure 2 . Comparative analysis revealed that the psychrophilic bacteria of the present invention Algoriphagus sp. CM16 model strain Algoriphaguswinogradskyi The 16S rRNA sequence similarity of LMG 21969 was 96.97%.

[0024] The inventors also used the ANI calculator to perform ANI (average nucleotide identity) comparative analysis on the whole genome model strains uploaded to the EzBioCloud database (see Figure 3 The results showed that the ANI of CM16 and all model strain genome sequences was lower than the interspecies identification standard of 95% on the website.

[0025] Example 3 Psychrotrophic bacteria ( Algoriphagus Growth curve of sp. CM16 2% seed solution (OD 600 = 0.7) was inoculated into 2216E liquid medium and cultured in a shaker at 15°C, 20°C, 25°C, 30°C and 35°C (180 rpm). 200 μl of bacterial solution was taken at regular intervals and measured for absorbance in a microplate reader at a wavelength of 600 nm. Three parallels were set up for each group. The blank control group used sterile seawater instead of seed solution, and the rest was the same as the experimental group. Samples were taken at different times, OD600 values ​​were measured, and growth curves were drawn (see Figure 4 ). Figure 4 It can be seen that the optimum growth temperature of CM16 is between 25 and 30°C.

[0026] Culture medium (g / 100 mL): peptone 0.5 g, yeast 0.1 g, Fe2(PO4)30.001 g, artificial seawater 100 mL, pH 7.8, i.e., 2216 E liquid culture medium.

[0027] Example 4 Psychrotrophic bacteria ( Algoriphagus Growth curve of sp. CM16 Ultrapure water was used instead of artificial seawater to prepare 2216E culture medium with NaCl concentrations of 0%, 3%, 6%, 9%, 12% and 15% (w / v). 2% of the seed solution was inoculated and placed in a 25°C shaker for culture (180 rpm). 200 μl of the bacterial solution was taken out at regular intervals and the absorbance was measured by an ELISA reader at a wavelength of 600 nm. Three parallels were used for each group. The blank control used sterile seawater instead of seed solution, and the rest was the same as the experimental group. Samples were taken at different times, the OD600 value was measured, and the growth curve was drawn (see Figure 5 ). Figure 5 The results showed that the optimum growth salinity of CM16 was between 3% and 6%.

[0028] Example 5 Psychrotrophic bacteria ( Algoriphagus Cr(VI) reduction ability of sp. CM16 Prepare 2216E medium containing 50 mg / L Cr(VI), inoculate 2% of the seed solution and culture at 20℃, 25℃, 30℃ and 35℃ in a shaker (180 rpm). Remove 1 mL of the bacterial solution at regular intervals and centrifuge to collect the supernatant. Detect the Cr(VI) concentration in the supernatant using the method described below and make a curve (see Figure 6 ). Three parallels were measured in each group, and the blank control was replaced by sterile seawater instead of seed solution.

[0029] The content of Cr(VI) in the supernatant after centrifugation was determined by diphenylcarbazide spectrophotometry. 100 μl of the supernatant was placed in a 10 mL EP tube, and ultrapure water was added to 1 mL. 50 μl of sulfuric acid solution (1:1) and 50 μl of phosphoric acid solution (1:1) were added in sequence, and the volume was adjusted to 5 mL. 200 μl of diphenylcarbazide colorimetric solution was added, and the mixture was shaken. After 10 min, the sample was tested on an ELISA reader at a wavelength of 540 nm. The absorbance was measured with water as a reference. The content of hexavalent chromium was obtained from the standard curve.

[0030] Attached Figure 6 The results show that the optimum Cr(VI) reduction temperature of CM16 is between 25 and 30℃.

[0031] Example 6 Psychrotrophic bacteria ( Algoriphagus Cr(VI) reduction ability of sp. CM16 Ultrapure water was used instead of artificial seawater to prepare 2216E medium containing 50 mg / LCr(VI) at NaCl concentrations of 0%, 3%, 6% and 9% (w / v). 2% of the seed solution was inoculated and placed in a shaker at 25°C for culture (180 rpm). 1 mL of the bacterial solution was removed at regular intervals and centrifuged to collect the supernatant. The Cr(VI) concentration was detected using the method described in Example 5, and a curve was prepared (see Figure 7 ). Three parallels were measured in each group, and the blank control was replaced by sterile seawater instead of seed solution.

[0032] Attached Figure 7 The results show that the optimum salinity for Cr(VI) reduction of CM16 is between 3% and 6%, and the reduction efficiency is still over 70% when the salinity reaches 6%.

[0033] Example 7 Effects of different carbon sources on psychrophilic bacteria ( Algoriphagus sp.)CM16 Cr(VI) reducing ability Prepare 2216E medium containing 50 mg / L Cr(VI), and add glucose, sucrose, sodium lactate, sodium pyruvate, mannitol, sodium citrate, sodium acetate and glycerol respectively to adjust the final concentration to 1 g / L, inoculate 2% of the seed solution respectively and place in a 25°C shaker for culture (180 rpm), remove 1 mL of the bacterial solution at regular intervals, centrifuge and collect the supernatant, detect the Cr(VI) concentration therein by the method described in Example 5, and make a curve (see Figure 8 ). Three parallels were measured in each group, and the blank control was replaced by sterile seawater instead of seed solution.

[0034] Attached Figure 8 The results showed that among the eight common carbon sources selected in this experiment, glucose, sucrose and sodium acetate had no significant effect on the Cr(VI) reduction efficiency of CM16, while sodium lactate, sodium pyruvate and sodium citrate had a significant promoting effect on the Cr(VI) reduction of CM16.

[0035] Example 8 Effects of different electron acceptors on psychrophilic bacteria ( Algoriphagus sp.)CM16 Cr(VI) reducing ability Prepare 2216E medium containing 50 mg / L Cr(VI), add sodium nitrate, sodium nitrite, sodium sulfate, and sodium thiosulfate, respectively, inoculate 2% of the seed solution, and culture in a shaker at 25°C (180 rpm). Remove 1 mL of the bacterial solution at regular intervals and centrifuge to collect the supernatant. Detect the Cr(VI) concentration therein by the method described in Example 5, and prepare a curve (see Fig. 9 ). Three parallels were measured in each group, and the blank control was replaced by sterile seawater instead of seed solution.

[0036] Attached Fig. 9 It shows that S2O3 2- It has a significant inhibition on the reduction of Cr(VI) in CM16, with an inhibition rate of up to 99%. 2- The inhibitory effect on Cr(VI) reduction of CM16 was small, and NO3 2- 、SO4 2- It has little effect on the Cr(VI) reduction efficiency of CM16.

[0037] Example 9 Effects of coexistence of different heavy metal ions on psychrophilic bacteria ( Algoriphagus sp.)CM16 Cr(VI) reducing ability Prepare 2216E medium containing 50 mg / L Cr(VI), and add ferric chloride, copper sulfate, manganese sulfate, zinc sulfate, tin chloride, nickel sulfate, barium chloride and lead nitrate respectively, adjust the metal ion concentration to 500 μg / L, inoculate 2% of the seed solution respectively, place in a 25°C shaker for culture (180 rpm), remove 1 mL of the bacterial solution at regular intervals, centrifuge and collect the supernatant, detect the Cr(VI) concentration therein by the method described in Example 5, and make a curve (see Fig.10 ). Three parallels were measured in each group, and the blank control was replaced by sterile seawater instead of seed solution.

[0038] Attached Fig.10 It shows that the 8 metal ions Cu tested in this study 2+ , Pb 2+ , Fe 3+ Sn 2+ 、Zn 2+ , Mn 2+ 、Ni 2 + , Ba 2+ None of them affect the reduction of Cr(VI) by CM16.

[0039] Example 10 Psychrotrophic bacteria Algoriphagus Tolerance concentration of Cr(VI) in CM16 100 μL of psychrotrophic bacteria ( Algoriphagus sp.) CM16 cultures (OD600 = 0.8-1.0) were placed in 2216E medium containing the following Cr(VI) concentrations: 0, 50, 100, 150, 200, 250, 300 mg / L. These cultures were incubated at 25°C in a rotary shaker at 180 rpm using medium without Cr(VI) as a blank, and samples (0.2 mL each) were removed at regular intervals to measure the absorbance at OD600 (see Fig.11 ).

[0040] Attached Fig.11 The results showed that the maximum tolerance concentration of CM16 to Cr(VI) was 250 mg / L.

[0041] Embodiment 11 Halobacterium psychrotrophicum Algoriphagus Cr(VI) scavenging effects of resting cells, heat-treated cells and spent culture medium of CM16 The psychrotrophic bacteria ( Algoriphagus sp.) CM16 cells were treated into three parts. The bacterial solution was centrifuged at 8000 rpm for 10 min at 4°C, the bacteria were collected, and the supernatant was filtered through a 0.22 µm filter membrane as the extracellular extract. The collected cells were washed repeatedly three times with Tris-HCl buffer to remove impurities in the supernatant and divided into two parts. One part dissolved the cell pellet in 50 mM Tris-HCl (pH 7.0) buffer to obtain a stationary cell suspension, and the other part was prepared into heat-killed cells by incubating at 80°C for 30 min. K2Cr2O7 was added to the cell suspension to make the final Cr(VI) concentration of 20 mg / L. Incubate at 180 rpm at 25°C, and detect the concentration of Cr(VI) in the supernatant at different intervals (see Fig.12 ).

[0042] Attached Fig.12 The results showed that the removal ability of CM16 for Cr(VI) mainly came from the reduction reaction mediated by related enzymes.

[0043] Example 12 Psychrotrophic bacteria Algoriphagus Cr(VI) scavenging effects of permeable cells and different cell components of CM16 Wash and resuspend the psychrotrophic bacteria ( Algoriphagus sp.) CM16 resting cell suspension was treated with 0.2% (v / v) toluene and 0.01% (v / v) Triton X-100 to prepare permeable cells. After the resting cells were washed and disrupted in 50 mM Tris-HCl, the cells were disrupted by ultrasound in an ice bath for a total of 20 minutes (200 W, ultrasound for 4 seconds, intervals of 2 seconds). The sonicated suspension was centrifuged at 8000 rpm for a total of 10 min at 4°C to remove unbroken cells or cell debris. The supernatant was centrifuged at 12000 rpm for 30 min, the supernatant was taken as the cytoplasmic fraction, and the precipitate was resuspended in Tris-HCl buffer to obtain the wall membrane fraction. Sodium lactate was used as an electron donor for in vitro determination of Cr(VI) reductase activity (see Fig.13 ).

[0044] Attached Fig.13The results showed that there were relevant chromium reductases in the cytoplasm and cell wall membrane of CM16, which were used to reduce Cr(VI).

[0045] Example 13 Psychrotrophic bacteria Algoriphagus Oxidative stress response of CM16 to Cr(VI) CM16 cells in the logarithmic growth phase were collected, washed three times with sterile artificial seawater, and divided into five parts. 0, 20, 40, 60, 80 mg / L Cr(VI) and 5 g / L sodium lactate were added respectively, and cultured in a constant temperature shaker at 25°C, 180 rpm for 2 h. The cells were collected again, washed three times with 0.05 M PBS buffer, resuspended in liquid nitrogen disruption solution, added with 2 mg / L lysozyme, and ice-bathed for 1 h, and then placed in liquid nitrogen for quick freezing. After complete solidification, they were melted in a 30°C water bath, shaken continuously during the period, and then placed in liquid nitrogen again. The above steps were repeated 6 times. After the solution became viscous, the supernatant was collected by centrifugation at 12000 rpm for 20 min at 4°C and stored at -80°C for later use.

[0046] The MDA content, superoxide dismutase (SOD) activity, and catalase (CAT) activity in the samples prepared above were determined using the Bio-Tian lipid peroxidation assay kit, catalase assay kit, and total SOD activity assay kit according to the instructions. Fig.14 , 15 , 16).

[0047] Attached Fig.14 , 15 , 16 showed that the MDA content, superoxide dismutase (SOD) activity, and catalase (CAT) activity in CM16 cells all showed a significant upward trend with the increase of Cr(VI) concentration, indicating that CM16 exerted a strong antioxidant capacity in the process of reducing Cr(VI).

Claims

1. A psychrophilic bacterium, characterized in that: The psychrophilic bacteria are classified and named as ( Algoriphagus sp.) CM16, deposited in the China Center for Type Culture Collection on October 23, 2024, with the deposit number CCTCC NO: M20242309.

2. The psychrophilic bacteria according to claim 1, characterized in that The 16S rDNA nucleotide sequence of the psychrophilic bacteria is shown in SEQ ID NO:

1.

3. A bacterial agent comprising the psychrotrophic bacteria as claimed in claim 1.

4. The bacterial agent according to claim 3, characterized in that The bacterial agent is solid or liquid.

5. The bacterial agent according to claim 3, characterized in that The bacterial agent contains fermentation liquid of psychrophilic bacteria.

6. Use of the psychrotrophic bacteria as claimed in claim 1 or the bacterial agent as claimed in claim 3 in reducing Cr(VI).

7. Use of the psychrotrophic bacteria as claimed in claim 1 or the bacterial agent as claimed in claim 3 in reducing Cr(VI) to Cr(III).

8. Use of the psychrotrophic bacteria according to claim 1 or the bacterial agent according to claim 3 in reducing Cr(VI) to Cr(III) in the presence of a salt solution, characterized in that: The concentration of the salt solution is ≤9%.

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