A strain of hexavalent chromium-reducing bacteria and its application

Abstract

The invention discloses a hexavalent chromium-reducing bacteria and its application, belonging to the field of biotechnology. The hexavalent chromium-reducing bacteria is Pseudomonas chengduensis JGM2, whose preservation number is CGMCC No.25221, and can be applied to reduce hexavalent chromium to treat chromium pollution, and the method is to inoculate the hexavalent chromium-reducing bacteria into a system containing hexavalent chromium and cultivate it to achieve the reduction of hexavalent chromium. By cultivating the hexavalent chromium-reducing bacteria of the invention, the pollution of hexavalent chromium in the water and soil environment can be treated, and the harm of hexavalent chromium to the environment, humans, animals and plants can be reduced.

Description

Technical Field

[0001] The invention relates to the field of biotechnology, in particular to a hexavalent chromium-reducing bacterium and application thereof. Background Art

[0002] Heavy metal chromium is an important industrial raw material. It has a wide range of applications in the leather industry, textiles, electroplating and dyes, and has great economic value. However, it is extremely toxic and easily causes environmental pollution. my country is one of the world's largest producers of chromium salts. If the chromium slag produced by chromium salt production plants is not properly stacked and landfilled, the soluble hexavalent chromium (Cr (VI)) ions contained in it will dissolve in rainwater and then transfer to water and soil environments to cause pollution; in addition, improper discharge of wastewater from electroplating, dyes, leather tanning, textiles and other industries will cause chromium to enter the environment; and improper treatment of waste gas and particulate matter of various sizes generated in the production process of pesticides and metallurgy may also cause chromium pollution. According to statistics, the concentration of chromium pollution in my country's agricultural fields is relatively high, and in some areas it can be as high as 820 mg / kg, which is seriously exceeded. Due to the continuous circulation and flow of substances in the environment between various spheres, heavy metal chromium gradually accumulates in the environment after a series of actions, causing the chromium content in the environment to continue to increase, even far exceeding its background value, resulting in the deterioration of environmental quality and pollution.

[0003] Compared with Cr(III), Cr(VI), which has strong oxidizing and migration properties, is more toxic, up to 100 times more toxic than Cr(III). This level of toxicity is seriously carcinogenic to human cells, and will be absorbed and accumulated in the body, which is seriously destructive and mutagenic to the normal functions of human cells. The harm caused by Cr(VI) to plants should not be underestimated. Similar to toxic heavy metals, it will mainly concentrate in the roots, thereby inhibiting the root system from absorbing nutrients and affecting the upward transport of nutrients from the roots, making it impossible for plants to metabolize normally, which is manifested as difficulty in plant growth and development being hindered. The harm of Cr(VI) is so great that it deserves our greater attention.

[0004] In order to solve the Cr(VI) pollution problem, how to remove residual Cr(VI) in the environmental system has become a research hotspot in recent years. At present, a lot of research and practice have been carried out on the physical and chemical treatment methods containing Cr(VI). Although the current physical and chemical methods can effectively remove Cr(VI) in the environment, they usually have high operating environment requirements and high costs. They may also damage the soil structure and cause secondary pollution. They are relatively difficult to control and have certain limitations. Compared with these two methods, the microbial reduction method can perform in situ, ex situ or in situ / ex situ combined remediation of Cr(VI) in the contaminated environment. At the same time, this method is low in cost and high in efficiency, relatively environmentally friendly, and meets the requirements of sustainable development. However, there are currently few Cr(VI) reducing bacteria on the market, with low reduction ability and limited selectivity. Summary of the invention

[0005] In order to make up for the shortcomings of the prior art, a strain with high Cr(VI) reduction ability under aerobic conditions and optimized conditions for reducing Cr(VI) by the strain are provided.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a hexavalent chromium-reducing bacterium (Pseudomonas chengduensis) JGM2, whose preservation number is CGMCC No.25221, which belongs to Pseudomonas chengduensis, and has been preserved in the General Microbiology Center of China Culture Collection of Microorganisms on July 1, 2022, address: No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, General Microbiology Center of China Culture Collection of Microorganisms.

[0008] The present invention also provides the use of the hexavalent chromium-reducing bacteria in reducing hexavalent chromium to trivalent chromium, so as to reduce the toxicity of chromium in the environment.

[0009] Preferably, the method comprises the following steps: inoculating hexavalent chromium-reducing bacteria into an environment containing hexavalent chromium to achieve reduction of hexavalent chromium.

[0010] Preferably, the inoculation conditions are: the concentration of hexavalent chromium is 50-200 mg / L, the inoculation amount of hexavalent chromium-reducing bacteria is 1-8%, and the pH is 5-10.

[0011] Preferably, the inoculation conditions are: the concentration of hexavalent chromium is 50 mg / L, the inoculation amount of hexavalent chromium-reducing bacteria is 8%, and the pH is 8.

[0012] Preferably, before inoculating into a system containing hexavalent chromium, the method further includes pre-culturing the hexavalent chromium-reducing strain, inoculating the hexavalent chromium-reducing strain into a nutrient broth medium and culturing for about 24 hours.

[0013] Preferably, the reduction rate of hexavalent chromium by hexavalent chromium-reducing bacteria reaches 90%.

[0014] The invention also provides a chromium reducing agent, comprising hexavalent chromium reducing bacteria.

[0015] The invention also provides a reagent for preventing chromium pollution, comprising hexavalent chromium-reducing bacteria.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] The hexavalent chromium-reducing bacteria JGM2 screened by the present invention can achieve a hexavalent chromium reduction rate of 90%. It can be specially cultured and inoculated into a system containing hexavalent chromium to effectively, quickly and efficiently reduce the hexavalent chromium therein. Therefore, it can be applied to soil contaminated by hexavalent chromium, chromium-containing electroplating wastewater and other environments to reduce the serious harm caused by hexavalent chromium to the natural environment, animals, plants and human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention, in which:

[0019] Figure 1 This is a graph showing the reduction effect of four hexavalent chromium-reducing bacteria initially screened in the present invention on hexavalent chromium Cr(VI), wherein the abscissas 1 to 4 represent JGM1 to JGM4, respectively;

[0020] Figure 2 The effect of inoculum size on the reduction of Cr(VI) by the hexavalent chromium-reducing strain JGM2;

[0021] Figure 3 The effect of initial Cr(VI) concentration on the reduction of Cr(VI) by the hexavalent chromium-reducing strain JGM2;

[0022] Figure 4 The effect of pH on the reduction of Cr(VI) by the hexavalent chromium-reducing strain JGM2 provided by the present invention;

[0023] Figure 5 This is the colony morphology of the hexavalent chromium-reducing strain JGM2;

[0024] Figure 6 This is the Gram staining result of hexavalent chromium-reducing bacteria JGM2;

[0025] Figure 7 Phylogenetic tree of the hexavalent chromium-reducing strain JGM2. DETAILED DESCRIPTION

[0026] The disclosure below provides many different embodiments or examples to implement different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0027] Reagents and materials used in the examples:

[0028] Table 1 List of main reagents

[0029]

[0030]

[0031] Screening material of hexavalent chromium-reducing strains: activated sludge from Qinhuangdao sewage treatment plant.

[0032] Experimental example

[0033] 1. Screening of hexavalent chromium-reducing bacteria

[0034] (1) Activation and enrichment of bacterial sources: Take 10g of activated sludge sample in a conical flask, add a certain amount of glucose, shake well, and take another 10g of activated sludge sample in a conical flask without adding glucose. Put the two groups of sewage samples into a constant temperature oscillator for cultivation, set the temperature of the constant temperature oscillator to 35℃ and the speed to 150r / min. Let it stand for a while, and take the supernatant for subsequent experiments.

[0035] (2) Isolation and purification of hexavalent chromium-reducing strains: On a clean bench, add 9 mL of sterile water to a sterilized test tube, take 1 mL of each of the two groups of treated sewage samples and add them to the test tubes. After mixing, use a pipette to transfer 1 mL of the high-concentration test tube to perform gradient dilution. Then, use a pipette to transfer 100 μL of the dilution factor of 10 to each of the two groups of treated sewage samples. -1 , 10 -3 , 10 -5 , 10 -7 , 10 -8 , 10 -9The diluted liquid is then spread evenly on the plate through a spreader, and the plate is inverted in a 35°C constant temperature incubator for a certain period of constant temperature incubation until a single colony appears on the surface of the plate. Subsequently, under sterile conditions, the single colony is placed on a solid culture medium for line separation to purify it. Specifically, three plates are drawn for each strain of bacteria, and the plates are inverted in a 35°C constant temperature incubator. This process is continued until single colonies with consistent morphological characteristics appear on the solid culture medium, and finally 4 strains of hexavalent chromium-reducing bacteria are obtained, which are named: JGM1, JGM2, JGM3, and JGM4. After that, the single colony can be streaked, inoculated on the slant culture medium, and placed in a refrigerator for refrigerated storage.

[0036] (3) Screening of hexavalent chromium-reducing strains: On a clean bench, different colonies on the solid plate were picked out with an inoculation loop, enriched and cultured in NB medium for 24 h, and then inoculated into NB medium containing 100 mg / L Cr(VI) at an inoculation volume of 1%. After culturing for 2 and 4 days, samples were taken to detect the residual Cr(VI) concentration in the culture medium and the reduction rate was calculated. The results are shown in Table 1. Figure 1 As shown in the figure, the reduction rate of Cr(VI) by hexavalent chromium-reducing strains increased with the extension of time. By comparing the Cr(VI) reduction rates of different hexavalent chromium-reducing strains, it was found that the reduction capacity of the four hexavalent chromium-reducing bacteria was: JGM2>JGM1>JGM4>JGM3. Among them, the hexavalent chromium-reducing strain JGM2 had the strongest reduction capacity, and the reduction rate reached more than 30% on the 4th day, so JGM2 was used as the hexavalent chromium-reducing bacteria for subsequent optimization experiments.

[0037] 2. Study on Optimization of Strain Reduction Conditions

[0038] The controlled variable method was used to study the effects of inoculation size, initial Cr(VI) concentration and pH on the growth and reduction performance of the hexavalent chromium-reducing strain, so as to optimize the reduction conditions of the strain and improve its reducing ability.

[0039] (1) Effect of inoculum size on growth and reduction of JGM2 strains

[0040] NB medium was selected, pH was adjusted to 7.0, JGM2 bacterial suspension was inoculated into NB medium at 1%, 2%, 3%, 4%, 5%, and 8% inoculation, Cr(VI) concentration was adjusted to 50 mg / L, and the liquid volume in the conical flask was 100 mL. It was cultured in a constant temperature oscillator at 35°C and 150 r / min. After 1d, 3d, 5d, and 7d of culture, samples were taken to determine the residual Cr(VI) content and the absorbance of the cells at OD600, and the reduction rate was calculated to explore the effect of inoculation amount on the growth and reduction effect of JGM2 strain; three parallel experiments were performed.

[0041] like Figure 2 As shown in the figure, the efficiency of JGM2 strain in reducing Cr(VI) increases with the increase of inoculum size. When the inoculum size is 1%, the reduction rate is above 60% after 7 days. This may be due to the small inoculum size, which leads to a small overall biomass of the strain in the culture medium, and the reduction effect of Cr(VI) is not as good as that of the group with a higher inoculum size. With the increase of inoculum size, the reduction rate increases but the difference is not large. The reduction rate is the highest when the inoculum size is 8%. This may be because Cr(VI) is toxic to the strain JGM2. When the inoculum size increases, more microorganisms reduce Cr(VI). At the same time, with the increase of inoculum size, the JGM2 bacteria itself can produce a mechanism to cope with adverse environments and overcome the adverse factors in the system. However, in a specific culture system, due to limited nutrients, bacteria cannot continue to proliferate. With the lack of nutrients and the accumulation of metabolites, saturation will be reached, and the reduction effect of Cr(VI) will no longer change significantly. Therefore, when using microorganisms to reduce Cr(VI), the appropriate inoculum size is crucial to the growth of JGM2 strains and the reduction of Cr(VI). The appropriate inoculum size is 8%. However, considering aspects such as cost saving and improving operation efficiency, 1% inoculation amount was used as the inoculation amount in this experiment.

[0042] (2) Effect of initial Cr(VI) concentration on the growth and reduction of JGM2 strain

[0043] NB medium was selected, pH was adjusted to 7.0, and JGM2 bacterial suspension was inoculated into NB medium containing Cr(VI) concentrations of 50mg / L, 100mg / L, 200mg / L, 400mg / L, 800mg / L, and 1600mg / L at a 1% inoculation volume, and the liquid volume in the conical flask was 100mL. It was cultured in a constant temperature oscillator at a temperature of 35°C and a speed of 150r / min. After 1d, 3d, 5d, and 7d of culture, samples were taken to determine the residual Cr(VI) content and the absorbance of the cells at OD600, and the reduction rate was calculated to explore the effect of inoculation volume on the growth and reduction effect of JGM2 strains; three sets of parallel experiments were performed.

[0044] like Figure 3As shown in the figure, the efficiency of reducing Cr(VI) by JGM2 strain varies greatly with different initial Cr(VI) concentrations. In general, the higher the initial Cr(VI) concentration, the lower the reduction rate. When the initial Cr(VI) concentration is low, JGM2 strain can maintain a reduction rate of more than 60% for Cr(VI). When the initial Cr(VI) concentration is 50 mg / L, the reduction rate is the highest, so 50 mg / L is used as the initial Cr(VI) concentration for subsequent experiments. When the Cr(VI) concentration is increased to 200 mg / L, the reduction rate drops to half of the reduction rate of low concentration Cr(VI). When the concentration is greater than 400 mg / L, the reduction rate is about 10%, indicating that high concentrations of Cr (VI) may have a toxic effect on the strain, causing the denaturation of intracellular proteins, reduced enzyme activity, and inhibiting the normal growth of JGM2 strain, ultimately resulting in a significant reduction in its reduction rate of Cr(VI). When the initial Cr(VI) was 800 mg / L, the JGM2 strain still had a low reduction rate for Cr(VI). When the initial Cr(VI) was 1600 mg / L, on the 7th day, the JGM2 strain had a reduction rate of about 5% for Cr(VI), which was almost ineffective. This shows that the concentration of Cr(VI) in the environment has a significant effect on the reduction effect of the JGM2 strain, and the appropriate initial Cr(VI) concentration is 50 mg / L.

[0045] (3) Effect of pH concentration on the growth and reduction of hexavalent chromium-reducing bacteria

[0046] NB medium was selected, and the pH was adjusted to 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0, respectively. The JGM2 bacterial suspension was inoculated into the NB medium with an inoculation amount of 1%, and the Cr(VI) was adjusted to 100 mg / L. The liquid volume in the conical flask was 100 mL. The culture was placed in a constant temperature oscillator at a temperature of 35°C and a speed of 150 r / min. After 1d, 2d, 3d, 4d, 5d, 6d, and 7d of culture, the residual Cr(VI) content and the OD600 value of the JGM2 bacterial solution were sampled and measured, and the reduction rate was calculated to explore the effect of pH on the growth and reduction effect of the JGM2 strain; three parallel experiments were performed.

[0047] like Figure 4As shown in the figure, different pH values ​​have a great difference in the efficiency of JGM2 strain reducing Cr(VI). When the pH is 4, the reduction rate of Cr(VI) is less than 20% within 7 days, and the reduction rate tends to be stable as time goes by, indicating that the growth of JGM2 strain under this condition is limited and the ability to reduce Cr(VI) is weak. There are two possible reasons. On the one hand, the acidic conditions themselves may affect the growth of JGM2 strain and thus affect the reduction of Cr(VI); on the other hand, it may be that the acidic conditions will increase the oxidizability of Cr(VI), which will increase its toxic effect on JGM2 strain, greatly affecting the growth of JGM2 strain and reducing its efficiency of reducing Cr(VI). As the pH gradually increases, the reduction rate also gradually increases. When pH=5-7, the reduction rate reaches more than 60% on the 7th day. When the pH is 8, the reduction rate reaches 90% after 7 days, reaching the maximum, indicating that the alkaline environment is more suitable for the growth of JGM2 and the reduction of Cr(VI), so pH=8 is taken as the optimal pH for the reduction of Cr(VI) by strain JGM2. As the pH continues to rise, the reduction rate begins to decline again. This may be because the excessively high pH inhibits the activity of certain enzymes in the JGM2 bacteria, impairing the enzyme function, thereby affecting the growth of JGM2 and further affecting the reduction efficiency of Cr(VI). This shows that strain JGM2 is sensitive to the pH value of the environment, and the suitable pH is 8.

[0048] 3. Identification of hexavalent chromium-reducing bacteria

[0049] (1) Morphological identification

[0050] 1) Population morphology identification

[0051] Take a certain amount of JGM2 bacterial solution of Cr(VI)-reducing bacteria, dilute it, separate it by streaking, and then culture it in a constant temperature oscillator at a temperature of 35°C and a speed of 150r / min for 24 hours. Select the plates with good single colonies, observe these plates, and record the performance of these colonies. Figure 5 As shown, the colonies of strain JGM2 are white, round and convex, with a colony diameter of about 1 mm, transparency and neat edges.

[0052] 2) Cell morphology identification - Gram staining

[0053] ① Fixation of smear. Use a rubber-tipped dropper to drop a drop of physiological saline into the center of a clean glass slide, pick up a small amount of culture with a sterilized inoculation loop, place it in the water drop on the glass slide, mix it with water to make a JGM2 bacterial suspension and spread it into a thin layer with a diameter of about 1 cm, and shake it back and forth above an alcohol lamp to fix it.

[0054] ② Add crystal violet solution on the bacterial film fixed on the slide to completely cover the bacterial film. The staining time is 1 minute.

[0055] ③ Wash with water. After staining for 1 minute, hold the slide at a 45° angle to the horizontal direction, and use a rubber-tipped dropper to squeeze out a small stream of water to wash away the excess dye on the bacterial film, while retaining the dye adsorbed by the bacteria.

[0056] ④ Mordant dyeing. Add a few drops of iodine solution to the coated surface of the slide and dye it for 1 minute. During this process, the iodine solution and the dye will form an insoluble substance, which can increase the affinity of the dye and bacteria.

[0057] ⑤ Wash with water. Rinse the slide slowly with distilled water until the water flowing down the slide is colorless, and then absorb the water with absorbent paper.

[0058] ⑥ Decolorization. Drop a few drops of decolorizing liquid on the coated surface, then shake it gently to decolorize it, wash it with water after 20 seconds, and then dry it with absorbent paper.

[0059] ⑦ Re-staining. Add a few drops of red re-staining solution to the surface. After re-staining for 1 minute, use a rubber-tipped dropper to squeeze out a small stream of water to rinse. After drying, use a microscope to observe the color of the cells.

[0060] The results are as follows Figure 6 As shown, the JGM2 strain was found to be short rod-shaped, and the cells appeared red after staining, indicating that the strain JGM2 was a Gram-negative bacterium.

[0061] (2) Molecular Biological Identification

[0062] 1) DNA extraction

[0063] Pick a small amount of purified JGM2 cells from the solid plate with a sterile toothpick, resuspend in 100 μL sterile ddH2O, and then boil in a boiling water bath for 10 min. After the above steps, immediately put it in a -20℃ refrigerator for 30 min, centrifuge at 12000 r / min for 1 min, and take the supernatant as the template.

[0064] 2) 16S rDNA amplification

[0065] The forward reaction primer was 27F (5'-AGAGTTTGATCCTGGCTCAG-3') (nucleic acid sequence as shown in SEQ ID NO.2), and the reverse reaction primer was 1492R (5'-GGTTACCTTGTTACGACTT-3') (nucleic acid sequence as shown in SEQ ID NO.3), and the primers were diluted to a 10 μM working solution.

[0066] ① Biological polymerase chain reaction (PCR) amplification system (26 μL) is shown in Table 2

[0067] Table 2 PCR amplification system

[0068]

[0069]

[0070] ②Reaction conditions are shown in Table 3

[0071] Table 3 PCR reaction conditions

[0072]

[0073] 3) 16S rDNA sequencing analysis

[0074] The PCR products were sent to Beijing Nosai Genome Research Center Co., Ltd. for sequencing analysis.

[0075] 4) Construction of phylogenetic tree

[0076] Using the NCBI database, the obtained nucleotide sequences were input into BLAST for comparison analysis to obtain the base sequences of strains related to the target strain. Subsequently, a phylogenetic tree was constructed in the MEGA software to analyze the relationship between strains and determine the strain type.

[0077] The gene sequence list of strain JGM2 is as follows (such as SEQ ID NO.1): CCATGCAGTCGAGCGGATGAGAGGAGCTTGCTCCTTGATTTAGCGGCGGACGGGTGAGTAATGCCTAGGAATCTGCCTGGTAGTGGGGGATAACGTCCGGAAACGGGCG CTAATACCGCATACGTCCTACGGGAGAAAGCAGGGGACCTTCGGGCCTTGCGCTA TCAGATGAGCCTAGGTCGGATTAGCTAGTTGGTGAGGTAATGGCTCACCAAGGCGACGATCCGTAACTGGTCTGAGAGGATGATCAGTCACACTGGAACTGAGACACGG TCCAGACTCCTACGGGAGGCAGCAGTGGGGAATATTGGACAATGGGCGAAAGCCTGATCCAGCCATGCCGCGTGTGTGAAGAAGGTCTTCGGATTGTAAAGCACTTTAA GTTGGGAGGAAGGGCATTAACCTAATACGTTAGTGTTTTGACGTTACCGACAGAATAAGCACCGGCTAACTTCGTGCCAGCAGCCGCGGTAATACGAAGGGTGCAAGCG TTAATCGGAATTACTGGGCGTAAAGCGCGCGTAGGTGGTTCGTTAAGTTGGATGTGAAAGCCCCGGGCTCAACCTGGGAACTGCATCCAAAACTGGCGAGCTAGAGTAC GGTAGAGGGTGGTGGAATTTCCTGTGTAGCGGTGAAATGCGTAGATATAGGAAG GAACACCAGTGGCGAAGGCGACCACCTGGACTGATACTGACACTGAGGTGCGAAAGCGTGGGGAGCAAACAGGATTAGATACCCTGGTAGTCCACGCCGTAAACGATGTCAACTAGCCGTTGGGTTCCTTGAGAACTTAGTGGCGCAGCTAACGCATTAAGTT GACCGCCTGGGGAGTACGGCCGCAAGGTTAAAACTCAAATGAATTGACGGGGGCCCGCACAAGCGGTGGAGCATGTGGTTTAATTCGAAGCAACGCGAAGAACCTTACCTGGCCTTGACATGCTGAGAACTTTCCAGAGATGGATTGGTGCCTTCGGGAGCTC AGACACAGGTGCTGCATGGCTGTCGTCAGCTCGTGTCGTGAGATGTTGGGTTAAGTCCCGTAACGAGCGCAACCCTTGTCCTTAGTTACCAGCACGTTATGGTGGGCACT CTAAGGAGACTGCCGGTGACAAACCGGAGGAAGGTGGGGATGACGTCAAGTCATCATGGCCCTTACGGCCAGGGCTACACACGTGCTACAATGGTCGGTACAAAGGGTT GCCAAGCCGCGAGGTGGAGCTAATCCCATAAAACCGATCGTAGTCCGGATCGCAGTCTGCAACTCGACTGCGTGAAGTCGGAATCGCTAGTAATCGTGAATCAGAATGTCACGGTGAATACGTTCCCGGGCCTTGTACACACCGCCCGTCACACCATGGGAGTG GGTTGCTCCAGAAGTAGCTAGTCTAACCTTCGGGGGGACGGTACCACGAA

[0078] The effective sequence length of the strain JGM2 gene obtained by sequencing was 1413 bp; after comparison with the NCBI website, a phylogenetic tree was constructed using the neighbor-joining method using Mega6.0 software ( Figure 7 ).

[0079] According to the sequence comparison results and phylogenetic tree theory, it was found that the strain JGM2 had the highest homology with the 16S rRNA gene of Pseudomonas chengduensis, reaching more than 99.9%, and they were stably clustered in the same branch. Therefore, JGM2 was determined to be Pseudomonas chengduensis.

[0080] Those skilled in the art will readily appreciate other embodiments of the invention after considering the specification and practicing the invention herein. The invention is intended to cover any variations, uses or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art of the invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0081] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A hexavalent chromium-reducing bacterium, characterized in that: The hexavalent chromium-reducing bacteria is Pseudomonas chengduensis ( Pseudomonas Chengduensis )JGM2, whose preservation number is CGMCC No.25221, and the inoculation condition of the hexavalent chromium-reducing bacteria is pH=5~10.

2. Use of the hexavalent chromium-reducing bacteria according to claim 1 in reducing hexavalent chromium to trivalent chromium, wherein the use is for non-therapeutic or diagnostic purposes.

3. The use of hexavalent chromium-reducing bacteria according to claim 2, characterized in that: The method comprises the following steps: inoculating the hexavalent chromium-reducing bacteria into an environment containing the hexavalent chromium to achieve reduction of the hexavalent chromium.

4. The use of hexavalent chromium-reducing bacteria according to claim 2, characterized in that: The inoculation conditions are as follows: the concentration of hexavalent chromium is 50-200 mg / L, and the inoculation amount of the hexavalent chromium-reducing bacteria is 1-8%.

5. The use of hexavalent chromium-reducing bacteria according to claim 4, characterized in that: The inoculation conditions are as follows: the concentration of hexavalent chromium is 50 mg / L, the inoculation amount of hexavalent chromium-reducing bacteria is 8%, and the pH is 8.

6. The use of hexavalent chromium-reducing bacteria according to claim 5, characterized in that: The reduction rate of the hexavalent chromium by the hexavalent chromium-reducing bacteria reaches 90%.

7. A chromium reducing agent, characterized in that: The invention comprises the hexavalent chromium-reducing bacteria as described in claim 1.

8. A reagent for preventing chromium pollution, characterized in that: The invention comprises the hexavalent chromium-reducing bacteria as described in claim 1.

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