Cadmium-resistant serratia marcescens from spider gut and application thereof

Abstract

The application provides a spider intestinal source high-cadmium-tolerant Serratia marcescens and application thereof. Serratia marcescens ) BJ827, which was preserved in the China General Microbiological Culture Collection Center on January 9, 2026, and has a preservation number of CGMCC No. 37348. The strain has stronger survival ability and stable application potential in a high-cadmium-polluted environment, breaks through the limitation that a traditional strain is difficult to apply in a high-concentration cadmium pollution scene, and provides an efficient and green functional microbial resource for in-situ bioremediation of cadmium-polluted water bodies and soil.

Description

Technical Field

[0001] This invention belongs to the field of environmental microbiology technology, and in particular relates to a highly cadmium-resistant Serratia marcescens from the spider gut and its applications. Background Technology

[0002] With the continuous advancement of industrialization and agricultural modernization, the problem of heavy metal cadmium pollution has become increasingly serious, posing a prominent environmental hazard to the stability of ecosystems and human health.

[0003] While traditional physicochemical remediation technologies such as chemical precipitation, ion exchange, and activated carbon adsorption have some applications among existing remediation methods, they generally suffer from technical shortcomings such as high cost, easy to cause secondary pollution, and difficulty in achieving in-situ remediation, making it difficult to meet the actual needs of current ecological and environmental governance.

[0004] In contrast, biosorption has attracted much attention due to its unique advantages. This technology relies on the specific binding of functional groups on the surface of microorganisms with heavy metal ions to achieve pollution control. It has significant characteristics such as being green and environmentally friendly, low cost, and capable of in-situ remediation, providing a promising new direction for the efficient treatment of heavy metal cadmium pollution. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and to develop a novel strain of Serratia marcescens with high cadmium tolerance and high adsorption capacity obtained through predator intestinal stress training. Another objective of this invention is to provide a method for isolating and screening this strain, optimizing the adsorption process, and its application in the in-situ remediation of cadmium-contaminated environments.

[0006] To solve the above-mentioned technical problems, the present invention provides a spider gut-derived, cadmium-resistant Serratia marcescens bacterium, wherein the spider gut-derived, cadmium-resistant Serratia marcescens bacterium is Serratia marcescens (… Serratia marcescens BJ827 was deposited on January 9, 2026, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 37348.

[0007] Based on a general technical concept, the present invention provides an application of the above-mentioned spider gut-derived highly cadmium-resistant Serratia marcescens in in-situ remediation of cadmium-contaminated environments.

[0008] The above application, further, the method of the application includes: S1. After activating Serratia marcescens strain BJ827, culture it to the logarithmic phase. S2. Inoculate the cadmium-contaminated water body to be remediated and cultivate it to achieve in-situ remediation of cadmium-contaminated environment.

[0009] In the above applications, the inoculum size of *Serratia marcescens* strain BJ827 is further 1% (v / v) to 5% (v / v). Further, the inoculum size is 2% (v / v) to 4% (v / v). Further, the inoculum size is 3% (v / v).

[0010] In the above application, further, the pH of the cadmium-contaminated water body to be remediated is 5-9. Further, the pH of the cadmium-contaminated water body to be remediated is 7.

[0011] In the above application, further, the cultivation in S2 is carried out in a shaker at 16℃ to 44℃ for 12h to 96h. Further, the cultivation is carried out in a shaker at 30℃ to 44℃ for 72h to 96h.

[0012] In the above application, further, the shaking speed is 80 rpm to 160 rpm. Further, the shaking speed for culture is 120 rpm to 160 rpm.

[0013] The above application, further, the application method is as follows: S1. After activating Serratia marcescens strain BJ827, culture it to the logarithmic phase. S2. Inoculate into the cadmium-contaminated water body to be remediated, adjust the pH to neutral, and incubate at 30℃ with a shaker at 120 rpm for 96 hours to achieve in-situ remediation of the cadmium-contaminated environment.

[0014] Based on a general technical concept, this invention provides the application of the above-mentioned spider gut-derived, highly cadmium-resistant Serratia marcescens in the preparation of a biosorbent for adsorbing cadmium. The carrier is one of diatomaceous earth, activated carbon, sodium alginate gel, and polyacrylamide.

[0015] Compared with the prior art, the advantages of the present invention are as follows: (1) This invention provides a highly cadmium-resistant Serratia marcescens from the spider gut, which can tolerate cadmium concentrations up to 80 mg / L. 2+ Single colonies are formed on solid culture media, and the tolerance to liquid culture is significantly better than that of conventional strains. It has stronger survival ability and stable application potential in high cadmium pollution environments, breaking through the limitation that traditional strains are difficult to apply in high-concentration cadmium pollution scenarios.

[0016] (2) This invention provides a highly cadmium-resistant Serratia marcescens from the spider gut, with a theoretical maximum adsorption capacity of 301.95 mg / g for cadmium (predicted by fitting the Langmuir adsorption model). Compared to existing cadmium-resistant strains, such as the Serratia marcescens disclosed in patent application CN117363514A, ( Serratia marcescensThe adsorption capacity of the RC strain increased by 7 times, which greatly improved the efficiency of cadmium pollution control, reduced the amount of treatment agents and treatment procedures, and significantly enhanced the economic efficiency of the treatment process.

[0017] (3) This invention provides a highly cadmium-resistant Serratia marcescens from the spider gut. The optimal pH for cadmium adsorption by the strain is 7.0 neutral conditions. It can also adapt to the pH environment of various complex systems such as natural water bodies and industrial wastewater. No additional acid-base adjustment pretreatment is required, which effectively broadens the practical application scenarios and reduces the engineering application cost.

[0018] (4) This invention provides a highly cadmium-resistant Serratia marcescens from the spider gut. Through desorption experiments, SEM-EDS, FTIR, XPS, TEM and other multi-scale characterization methods, the mechanism of cadmium adsorption by the strain was systematically elucidated. The functional groups such as hydroxyl, carboxyl and amino groups on the bacterial surface are related to Cd. 2+ The formation of Cd-O coordination bonds, mainly through chemical complexation, provides solid theoretical support for subsequent process optimization, equipment adaptation, and industrial application, and enhances the feasibility of technology transfer.

[0019] (5) This invention provides a highly cadmium-resistant Serratia marcescens from the spider gut. The strain is isolated from the special habitat of the spider gut, which endows the strain with unique adaptive evolutionary advantages, making it more competitive in extreme pollution environments. It also enriches the microbial resource bank and provides a new direction for the development of new pollution control microbial strains.

[0020] (6) This invention provides an application of *Serratia marcescens*, a spider gut-derived bacterium highly cadmium-resistant, in the remediation of cadmium-contaminated environments. In a 20 mg / L Cd solution, the removal rate reached 33.7%, the equilibrium adsorption capacity was 60.62 mg / g, and the Langmuir model predicted a theoretical maximum adsorption capacity of 301.95 mg / g. In an 80 mg / L Cd solution... 2+ Single colonies formed on solid culture media, and the strain showed significantly better tolerance to liquid culture than conventional strains.

[0021] A spider gut-derived, cadmium-resistant Serratia marcescens, wherein the spider gut-derived, cadmium-resistant Serratia marcescens is Serratia marcescens (… Serratia marcescens BJ827 was deposited on January 9, 2026, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 37348. Attached Figure Description

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0023] Figure 1 The images show the colony morphology (a) and Gram staining (b) of the *Serratia marcescens* strain BJ827 from Example 1.

[0024] Figure 2 This is the phylogenetic tree of Serratia marcescens strain BJ827 from Example 1.

[0025] Figure 3 For different Cd values ​​in Experiment 2 of this invention 2+ Growth curves of strain BJ827 at different concentrations.

[0026] Figure 4 For different Cd values ​​in Experiment 3 of this invention 2+ Initial removal rate at the specified concentration.

[0027] Figure 5 The inoculum amount and Cd in Experiment 4 of this invention 2+ Results of concentration cross-screening experiment.

[0028] Figure 6 The figure shows the effect of culture time on removal rate in Experiment 4 of this invention.

[0029] Figure 7 The results show the effect of culture temperature on the removal rate in Experiment 4 of this invention.

[0030] Figure 8 This is the result of the effect of initial pH on the removal rate in Experiment 4 of this invention.

[0031] Figure 9 The results show the effect of culture rotation speed on removal rate in Experiment 4 of this invention.

[0032] Figure 10 The results are the fitting results of the pseudo-first-order and pseudo-second-order dynamic models in Experiment 6 of this invention.

[0033] Figure 11 The results are the fitting results of the Langmuir and Freundlich isotherm models in Experiment 6 of this invention.

[0034] Figure 12 The desorption effects of different desorbents in Experiment 7 of this invention are shown.

[0035] Figure 13 The results are from the SEM-EDS analysis in Experiment 7 of this invention.

[0036] Figure 14 This is a comparison chart of FTIR spectra from Experiment Seven of this invention.

[0037] Figure 15 The XPS high-resolution spectra (C1s, O1s, Cd3d) in Experiment 7 of this invention.

[0038] Figure 16 This is the XPS full-spectrum scan image from Experiment Seven of this invention.

[0039] Figure 17 This is a TEM image from Experiment Seven of this invention. Detailed Implementation

[0040] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention. The materials, reagents, and instruments used in the following embodiments can all be purchased commercially. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods in the art.

[0041] The composition of LB solid medium is: peptone 10 g / L, yeast extract 5 g / L, NaCl 10 g / L, agar 20 g / L, pH 7.4.

[0042] The spiders used were Pardos apseudo annulata, collected from ponds surrounding the experimental fields of the Hunan Academy of Agricultural Sciences.

[0043] 1000 mg / L Cd 2+ Preparation method of standard stock solution: CdCl2 is selected as the solute. 2.5H2O and other common cadmium salts, the solvent is sterile deionized water, prepare and use immediately or store according to specifications.

[0044] Example 1 A type of spider gut-derived, cadmium-resistant Serratia marcescens is Serratia marcescens (Serratia marcescens). Serratia marcescens Strain BJ827 was deposited on January 9, 2026, at the China General Microbiological Culture Collection Center (CGMCC), accession number CGMCC No. 37348. This strain was isolated from *Pteranodon simianus* spiders reared under heavy metal cadmium stress. Pardosa pseudoannulata Intestinal contents.

[0045] The separation method includes the following steps: (1) Sample collection: Pardos apseudo annulata spiders were collected from ponds around the experimental field of Hunan Academy of Agricultural Sciences. The spiders were fed with fruit flies under heavy metal cadmium stress for 30 days, and their intestinal contents were collected by dissection.

[0046] (2) Gradual stress screening: Intestinal contents samples were serially diluted 10-fold with sterile physiological saline, and 10 samples were taken. -3 ~10 -5100 μL of each dilution was spread onto cadmium-free LB agar and incubated at 37°C for 48 h. Single colonies were then selected from plates exhibiting diverse colony morphologies and sequentially transferred to plates containing Cd. 2+ LB solid medium with concentrations of 20, 40, 60, 80, and 100 mg / L was used, and the medium was incubated at 37°C for 48 h at each gradient.

[0047] In the above steps, only 3-5 colonies survived on the 80 mg / L plate. The largest colony was selected and purified by streak cleaning five times to obtain a pure strain, named seqid1. This strain was then preserved and named *Serratia marcescens*. Serratia marcescens BJ827.

[0048] GenBank login ID: PQ780192.

[0049] Its gene sequence is shown in SEQ ID NO.1, specifically:

[0050] Experiment 1: Morphological and molecular identification of strain BJ827 from Example 1.

[0051] Figure 1 This is a colony morphology diagram of strain BJ827 from Example 1. Figure 1 a) and Gram staining diagram ( Figure 1 (b) in the middle.

[0052] from Figure 1 As can be seen from 'a', the colonies are 2-3 mm in diameter, with neat edges, smooth, moist, and glossy surfaces, ranging from milky white to light yellow, and some colonies are slightly raised.

[0053] from Figure 1 As shown in b, the bacteria are short rod-shaped, scattered or arranged in pairs, and stain pale red, indicating they are Gram-negative bacteria. No spores or capsules were observed under the microscope; the bacteria are uniform in shape and size.

[0054] 16S rDNA identification: Genomic DNA was extracted from BJ827 at a concentration of 236.2 ng / μL. 260 / A 280 =2.15. Amplification was performed using universal primers 27F / 1492R. The PCR products were sequenced and then assembled to obtain a 1425 bp sequence, the specific gene sequence of which is shown in SEQ ID NO.1. BLAST alignment showed... Serratia marcescens DFJ007 (OP947537.1) has a homology of 99%.

[0055] Figure 2 This is the phylogenetic tree of strain BJ827 from Example 1. Figure 2 The data shows that BJ827 clusters with the model strain.

[0056] Example 2 An application of strain BJ827 from Example 1 in the remediation of cadmium-contaminated environments. The application method includes: activating strain BJ827 and culturing it to the logarithmic phase; inoculating it into the cadmium-contaminated water body to be remediated at a 3% inoculum, adjusting the pH of the water body to 7, and culturing it in a shaker at 37°C for 97 h at a shaker speed of 120 rpm.

[0057] Experiment 2: To investigate the cadmium tolerance of strain BJ827 from Example 1.

[0058] Take several sterile conical flasks and add 100 mL of sterilized LB liquid culture medium to each flask. Then, aseptically add an appropriate amount of Cd to each flask. 2+ The stock solution was prepared to obtain Cd. 2+A series of culture media with final concentrations of 0 mg / L (control group), 20 mg / L, 40 mg / L, 60 mg / L, 80 mg / L, and 100 mg / L were prepared, with three biological replicates for each concentration. Seed culture of strain BJ827 was inoculated into each concentration of LB liquid medium at an inoculation volume of 1% (v / v). The inoculated conical flasks were placed in a constant-temperature shaker and cultured continuously at 37°C and 120 rpm for 60 h. Starting from the start of culture, aseptic samples of the culture medium from each concentration group were taken every 6 h, and the absorbance (OD) of the samples at 600 nm was measured using a UV-Vis spectrophotometer. 600 Record the OD values ​​at each time point and for each concentration group. 600 Data (each replicate sample was measured at least 3 times, and the average value was taken).

[0059] Inhibition rate (%) = [(Control group 60 h OD] 600 Average value - experimental group 60 h OD 600 (mean value) / control group 60 hOD 600 [Average] × 100%.

[0060] Tolerance Index (TI) = 60 h OD of the experimental group 600 Mean / Control Group 60 h OD 600 average value.

[0061] Different Cd 2+ The growth parameters of strain BJ827 at different concentrations are listed in Table 1.

[0062] Table 1: Different Cd 2+ Growth parameters of strain BJ827 at different concentrations.

[0063]

[0064] Note: Data are the mean ± standard deviation of three biological replicates.

[0065] Figure 3 For different Cd 2+ Growth curves of strain BJ827 at different concentrations; Note: The horizontal axis represents incubation time (h), and the vertical axis represents OD. 600 Values, each curve corresponds to a different Cd. 2+ Growth trend of concentration groups.

[0066] From Table 1 and Figure 3 The results showed that the control group (0 mg / L) entered a stable period after 24 hours, and the OD value was [missing value] at 60 hours. 600 The OD value reached 1.95 ± 0.03 in the 80 mg / L group over 60 hours. 600The value was 1.34±0.05, with an inhibition rate of 31.1%; the OD value of the 100 mg / L group was 60 h⁻¹. 600 The value was 1.24±0.04, with an inhibition rate of 36.4%, proving that the MIC of the strain was >80 mg / L.

[0067] Experiment 3: Effect of BJ827 strain on Cd 2+ Basic adsorption experiments.

[0068] The activated BJ827 strain was inoculated into LB liquid medium and cultured at 37°C and 120 rpm until the logarithmic growth phase. The OD of the bacterial culture was adjusted using a UV-Vis spectrophotometer. 600 The value was adjusted to 0.7 to obtain a standardized bacterial suspension for later use.

[0069] Take several sterile conical flasks and add 100 mL of sterilized LB liquid culture medium to each. Add an appropriate amount of Cd aseptically. 2+ The stock solution was prepared to obtain the initial Cd. 2+ A series of adsorption systems with concentrations of 20 mg / L, 40 mg / L, 60 mg / L, 80 mg / L, and 100 mg / L were established, with three biological replicates for each concentration.

[0070] The standardized bacterial suspension was added to each adsorption system at 1% (v / v) of the culture medium volume, and the conical flasks were placed in a constant temperature shaker and shaken at 37°C and 120 rpm for 48 h.

[0071] After the adsorption treatment, each system sample was centrifuged at 8000 rpm for 10 min, and the supernatant was collected. The remaining Cd in the supernatant was determined by atomic absorption spectrophotometry. 2+ concentration.

[0072] Removal rate (%) = [(initial Cd)] 2+ Concentration - Residual Cd 2+ Concentration) / Initial Cd 2+ [Concentration] × 100%.

[0073] Table 2 shows the effects of strain BJ827 on different concentrations of Cd. 2+ The initial removal rate.

[0074] Table 2: Effects of strain BJ827 on different concentrations of Cd² + The initial removal rate.

[0075]

[0076] Figure 4 For different Cd 2+ Initial removal rate at the specified concentration.

[0077] From Table 2 and Figure 4 The results showed that the 20 mg / L group had the highest removal rate, reaching 26.8% ± 1.2%; with increasing Cd concentration... 2+ As the concentration increased, the removal rate decreased, reaching 9.8% ± 0.5% in the 100 mg / L group; the removal amount increased with increasing concentration at low concentrations, and tended to saturate at 60 mg / L to 100 mg / L.

[0078] Experiment 4: Examining the stress screening conditions.

[0079] 4.1 Inoculation amount and Cd 2+ Concentration crossover experiment: After activating strain BJ827, culture it to the logarithmic growth phase; take a sterile conical flask, add 100 mL of sterile LB medium, and adjust the initial pH to 7 with hydrochloric acid or sodium hydroxide solution; add appropriate amounts of Cd. 2+ Stock solutions were prepared using the five concentration gradients of Cd mentioned above. 2+ -LB medium: 20, 40, 60, 80, 100 mg / L; inoculated at 5 different rates: 1%, 2%, 3%, 4%, 5% (v / v) into the corresponding Cd medium. 2+ The bacterial suspension was inoculated into the culture medium at a specific concentration and incubated at 37°C for 48 h in a constant-temperature shaker at 120 rpm. Samples were then centrifuged and the residual Cd was determined. 2+ Concentration and removal rate were calculated. Three biological replicates were set up for each group.

[0080] Figure 5 Inoculation amount and Cd 2+ The results of the concentration cross-screening experiment, from Figure 5 It can be seen from the low concentration of Cd 2+ Under the condition of (20 mg / L), the inoculum size significantly affected the removal rate: the removal rate reached 34.5% with an inoculum size of 3%, which was significantly higher than that of the 1% (P<0.05), 2% (P<0.05), 4% (P<0.05), and 5% (P<0.05) inoculum size groups, and was the optimal inoculum size at this concentration; for medium and high concentrations of Cd 2+ Within the range of (40–100 mg / L), the removal rate for all inoculum amounts increased with Cd. 2+ The removal rate decreased with increasing concentration, and there was no statistically significant difference in removal rate between different inoculum amounts at the same concentration (P>0.05); based on the removal rate data of 25 experimental groups, 20 mg / L Cd 2+ +3% inoculation rate is the globally optimal parameter combination, with the highest removal efficiency. Therefore, this combination is determined as the fixed condition for subsequent single-factor optimization experiments.

[0081] 4.2 Single-factor optimization of culture time: After activation, strain BJ827 was cultured to the logarithmic growth phase; 100 mL of sterile LB medium was added to a sterile conical flask, and the initial pH was adjusted to 7 with hydrochloric acid or sodium hydroxide solution; appropriate amounts of Cd were added respectively. 2+ Stock solution, prepared as 20 mg / L Cd 2+ -LB medium; inoculate at a rate of 3% (v / v) into the corresponding Cd medium. 2+ The bacterial suspension was inoculated into the culture medium at a specific concentration and placed in a constant-temperature shaker at 120 rpm for 48 h, 72 h, and 96 h at 37°C. Samples were then centrifuged and the residual Cd was determined. 2+ Concentration and removal rate were calculated. Three biological replicates were set up for each group.

[0082] Figure 6 The graph shows the effect of cultivation time on the removal rate. From... Figure 6 It can be seen that after 96 hours of cultivation, the strain showed resistance to Cd. 2+ The removal rate reached a peak of 33.1% ± 1.3%; the removal rate after 72 h of incubation was 31.8%, which was not statistically different from the 96 h group (P>0.05); the removal rate after 48 h of incubation was lower than the above two groups (specific values ​​can be supplemented based on experimental records), indicating that extending the incubation time to more than 72 h can improve the adsorption efficiency, but there is no significant gain after 96 h. Considering the overall efficiency, 96 h can be selected as the incubation time for subsequent experiments.

[0083] 4.3 Single-factor optimization of culture temperature: After activation, strain BJ827 was cultured to the logarithmic growth phase; 100 mL of sterile LB medium was added to a sterile conical flask, and the initial pH was adjusted to 7 with hydrochloric acid or sodium hydroxide solution; appropriate amounts of Cd were added respectively. 2+ Stock solution, prepared as 20 mg / L Cd 2+ -LB medium; inoculate at a rate of 3% (v / v) into the corresponding Cd medium. 2+ The bacterial suspension was inoculated into the culture medium at a concentration of [concentration] and placed in a constant-temperature shaker at 120 rpm. The cultures were then incubated at 30℃, 37℃, and 44℃ for 48 h, respectively. Samples were collected by centrifugation to determine the residual Cd. 2+ Concentration and removal rate were calculated. Three biological replicates were set up for each group.

[0084] Figure 7 The results show the effect of cultivation temperature on the removal rate. Figure 7 In this study, 37℃ was the optimal culture temperature for Cd. 2+ The removal rate reached 32.3% ± 1.4%; the removal rate at 30℃ was 30.5%, which was the second best temperature; the removal rate dropped significantly to 26.1% at 44℃, suggesting that high temperature may inhibit the activity of the strain and reduce the adsorption efficiency. Therefore, 37℃ was determined to be the optimal culture temperature.

[0085] 4.4 Initial pH Optimization: After activation, strain BJ827 was cultured to the logarithmic growth phase. A sterile conical flask was filled with 100 mL of sterile LB medium, and the initial pH was adjusted to 5, 7, and 9 respectively using hydrochloric acid or sodium hydroxide solution. An appropriate amount of Cd²⁺ was added. + Prepare a stock solution of 20 mg / L Cd 2+ -LB medium; inoculate at a rate of 3% (v / v) into the corresponding Cd medium. 2+ The bacterial suspension was inoculated into the culture medium at a specific concentration and incubated at 37°C for 48 h in a constant-temperature shaker at 120 rpm. Samples were then centrifuged and the residual Cd was determined. 2+ Concentration and removal rate were calculated. Three biological replicates were set up for each group.

[0086] Figure 8 The results show the effect of initial pH on the removal rate. Figure 8 In neutral conditions (pH 7), the strain is resistant to Cd²⁺. + The removal rate was the highest, reaching 34.8% ± 1.4%. Under acidic conditions (pH 5) and alkaline conditions (pH 9), the removal rates decreased significantly, to 23.2% and 25.3%, respectively. It is speculated that a pH deviation from neutrality will affect the cell wall charge properties or metabolic activity of the strain, thereby reducing the adsorption capacity. Therefore, the initial pH 7 was determined to be the optimal condition.

[0087] 4.5 Single-factor optimization of culture rotation speed: After activation, strain BJ827 was cultured to the logarithmic growth phase; 100 mL of sterile LB medium was added to a sterile conical flask, and the initial pH was adjusted to 7 with hydrochloric acid or sodium hydroxide solution; an appropriate amount of Cd was added. 2+ Prepare a stock solution of 20 mg / L Cd 2+ -LB medium; inoculate at a rate of 3% (v / v) into the corresponding Cd medium. 2+ Bacterial suspensions were inoculated into culture media of varying concentrations and placed in constant-temperature shakers at 80, 120, and 160 rpm, respectively, and incubated at 37°C for 48 h. Samples were then centrifuged and residual Cd was determined. 2+ Concentration and removal rate were calculated. Three biological replicates were set up for each group.

[0088] Figure 9 The effect of rotational speed on removal rate was investigated. The results showed that 120 rpm was optimal (30.2% ± 1.2%), while 80 rpm (26.5%) and 160 rpm (28.3%) were both lower.

[0089] Experiment 5: Orthogonal Experiment.

[0090] Using L9(3) 4An orthogonal array was used to investigate four factors at three levels: time (48, 72, 96 h), temperature (30℃, 37℃, 44℃), pH (6, 7, 8), and rotation speed (100 rpm, 120 rpm, 140 rpm). The inoculum size was fixed at 3%, and Cd was used. 2+ Concentration 20 mg / L.

[0091] The results of the orthogonal experiment are listed in Table 3.

[0092] Table 3: Results of orthogonal experiments and range analysis.

[0093]

[0094] Note: K1, K2, and K3 are the average removal rates corresponding to levels 1, 2, and 3 of each factor; R is the range. .

[0095] The results in Table 3 show that the order of influencing factors is time > pH > temperature > rotation speed; time is highly significant (P<0.01), while pH, temperature, and rotation speed are significant (P<0.05). The theoretically optimal combination is 96 h, 30℃, pH 7, and 120 rpm, under which the removal rate reaches 33.7% ± 1.2% (n=3), which is higher than all combinations in the orthogonal table.

[0096] Experiment 6: Dynamics and Isothermal Model Study.

[0097] Under optimal adsorption conditions (Cd) 2+ The Cd24 reaction was carried out under the following conditions: initial concentration 20 mg / L, inoculum size 3%, reaction temperature 30℃, initial pH 7, and shaker speed 120 rpm. 2+ Adsorption kinetics and isothermal adsorption model fitting study. 6.1 Adsorption Kinetics: Adsorption experiments were conducted under the above optimal conditions. Multiple time sampling points were set within the range of 0–96 h. After sampling, the samples were pretreated and detected, and the Cd at different times was calculated. 2+ Adsorption capacity. Pseudo-first-order and pseudo-second-order kinetic models were used to fit and analyze the experimental data.

[0098] Figure 10 It is a pseudo-level one ( Figure 10 a) and pseudo-secondary ( Figure 10 b) The fitting results of the dynamic model. Figure 10 The results show that the pseudo-second-order kinetic model has a higher fit to the adsorption process, with a higher correlation coefficient (R²). 2 =0.9606); the fitted theoretical equilibrium adsorption capacity is 60.62 mg / g, and the adsorption rate constant (k) is 0.9606. 2 =0.054h -1 Pseudo-second-order kinetic models are generally suitable for describing chemisorption processes, thus indicating that the strain in this experiment showed good chemisorption of Cd. 2+The adsorption is mainly dominated by chemical adsorption.

[0099] 6.2 Isothermal adsorption: Fix the inoculum amount of the strain at 3%, the reaction temperature at 30 °C, the initial pH of the system at 7, and the shaker speed at 120 rpm. Set the initial concentration of Cd 2+ to be in the gradient of 20 - 100 mg / L, and carry out isothermal adsorption experiments. After the adsorption reaction reaches equilibrium, take samples to measure the remaining concentration of Cd 2+ in the supernatant, and calculate the equilibrium adsorption capacity. Use the Langmuir isothermal adsorption model and the Freundlich isothermal adsorption model to fit the equilibrium adsorption data respectively.

[0100] Figure 11 For the fitting results of the Langmuir ( Figure 11 a in it) and Freundlich ( Figure 11 b in it) isothermal models. The figure shows that the Langmuir model has the best fit (R2 = 0.9919), the theoretical maximum adsorption capacity is 301.95 mg / g, and the separation factor RL = 0.020 (0 < RL < 1), indicating favorable adsorption.

[0101] Experiment 7: Multi-scale characterization experiment of adsorption mechanism.

[0102] To clarify the adsorption mechanism of the target bacteria on Cd, in this example, through desorption experiments combined with various microscopic characterization methods, multi-scale analysis is carried out from the macroscopic action type to the microscopic sites and bonding modes. The specific experimental process and results are as follows: 7.1 Desorption experiment: Use different desorbents to desorb the bacteria saturated with adsorbed Cd, and measure the desorption rate corresponding to each desorbent. Figure 12 For the desorption effects of different desorbents, it can be seen from Figure 12 that: the desorption rate of EDTA-Na2 is 76.0% ± 2.1%, which is significantly higher than that of KNO3 (43.8%) and ultrapure water (10.4%), confirming that chemical adsorption is the main one.

[0103] 7.2 SEM-EDS: Conduct SEM characterization and EDS element analysis on the bacteria before and after adsorbing Cd. Figure 13 For the SEM-EDS analysis results, Figure 13 a in Figure 13 is the surface morphology of the bacteria before adsorbing Cd; Figure 13 b in Figure 13In the figure, 'd' represents the elemental concentration detected by EDS after Cd adsorption. The results show that the mass fraction of Cd on the bacterial surface after Cd adsorption reached 1.47 wt%, while no Cd was detected in the control group of bacteria that did not adsorb Cd. These results directly confirm that Cd can be enriched on the bacterial surface through surface adsorption.

[0104] 7.3 FTIR: FTIR spectra were performed on the bacterial cells before and after Cd adsorption, and the peak shape and peak position changes of characteristic functional groups were compared and analyzed. Figure 14 This is a comparison of FTIR spectra. Line a represents the FTIR spectrum before adsorption, and line b represents the FTIR spectrum after adsorption. Figure 14 It can be seen from the data that after Cd adsorption, the infrared spectrum of the bacterial cells shows a correlation between OH / NH (3500 cm⁻¹). -1 C=O (1646 cm) -1 -COO - (1418 cm) -1 P=O (1242 cm) -1 COP (1095 cm) -1 The intensity of the related characteristic absorption peaks all decreased to varying degrees; meanwhile, at 617 cm⁻¹... -1 A new characteristic absorption peak (MO) appeared (M represents Cd). The above peak shape change confirms that multiple functional groups on the bacterial cell surface, such as hydroxyl, carboxyl, and phosphate groups, are involved in the coordination and binding process of Cd.

[0105] 7.4 XPS: XPS full-spectrum and high-resolution narrow-spectrum analysis was performed on the bacterial cells after Cd adsorption. Figure 15 This is a high-resolution XPS spectrum. Figure 15 In this context, 'a' represents the high-resolution narrow-spectrum C1s analysis before adsorption. Figure 15 In the figure, b represents the high-resolution narrow-spectrum C1s analysis after adsorption. Figure 15 In the figure, 'c' represents the high-resolution narrow-spectrum analysis of O1s before adsorption. Figure 15 In the figure, d represents the high-resolution narrow-spectrum analysis of O1s after adsorption. Figure 15 In the figure, 'e' represents the high-resolution narrow-spectrum analysis of Cd3d before adsorption. Figure 15 f in the figure represents the high-resolution narrow-spectrum analysis of Cd3d after adsorption. Figure 16 This is a full-spectrum XPS scan. Figure 16 In this context, 'a' represents the state before adsorption. Figure 16 In this context, 'b' represents the adsorption result.

[0106] As shown in the figure, the high-resolution narrow spectrum of Cd3d reveals characteristic peaks of Cd3d3 / 2 and Cd3d3 / 2 at 405.0 eV and 411.7 eV, respectively, corresponding to the characteristic binding energies of Cd. Further analysis of the C1s and O1s narrow spectra reveals a positive shift of 0.3 eV in the binding energy of the C=O bond after Cd adsorption, and a negative shift of 0.2 eV in the binding energy of the O1s bond. These shifts in binding energy confirm that Cd-O coordination bonds are formed between the O atoms in the functional groups on the bacterial cell surface and Cd.

[0107] 7.5 TEM: Ultrathin sections of bacterial cells before and after Cd adsorption were characterized by TEM. Figure 17 For TEM images, Figure 17 In the figure, 'a' represents the control group cells that did not adsorb Cd. Figure 17 In the diagram, b represents the bacterial cells in the experimental group after Cd adsorption. The results showed that the cell wall thickness of the control group without Cd adsorption was 20 nm–30 nm, while the cell wall thickness of the Cd-adsorbed cells increased to 40 nm–60 nm. Simultaneously, a large number of electron-dense particles of 5 nm–15 nm were observed in the periplasmic space. These morphological changes indicate that the cell wall is the main site for Cd adsorption, and Cd accumulates in the cell wall and periplasmic space.

[0108] Example 8: Investigating the adsorption capacity of heavy metal cadmium by strain BJ827.

[0109] Based on the excellent performance of strain BJ827 in simulated wastewater (20 mg / L Cd) of this invention 2+ The removal rate was 33.7%. The comparison results with other strains are shown in Table 4.

[0110] Table 4: Adsorption capacity of different strains for heavy metal cadmium.

[0111]

[0112] The results in Table 4 show that *Serratia marcescens* BJ827 has a good adsorption capacity for the heavy metal cadmium, indicating its potential application value. It is speculated that it has application potential in the treatment of cadmium-containing wastewater from electroplating, mining, and other industries. It is expected to be effective in the adsorption of cadmium. 2+ In actual wastewater with concentrations of 10 mg–50 mg / L and pH 6–8, this strain can achieve a removal rate of over 90% under optimized conditions (3% inoculum, 30℃, 120 rpm, 96 h), and the cadmium concentration after treatment is expected to be below 1.0 mg / L, approaching the requirements of the current national water pollutant discharge standards. Future research will focus on verifying the stability and reusability of this strain in the complex matrix of real industrial wastewater.

[0113] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A species of Serratia marcescens with highly cadmium-resistant gut-derived arachnid bacteria, characterized in that, The spider gut-derived, cadmium-resistant Serratia marcescens is Serratia marcescens (… Serratia marcescens BJ827 was deposited on January 9, 2026, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 37348.

2. The application of the spider gut-derived, highly cadmium-resistant Serratia marcescens as described in claim 1 in the in-situ remediation of cadmium-contaminated environments.

3. The application according to claim 2, characterized in that, The application method includes: S1. After activating Serratia marcescens strain BJ827, culture it to the logarithmic phase. S2. Inoculate the cadmium-contaminated water body to be remediated and cultivate it to achieve in-situ remediation of cadmium-contaminated environment.

4. The application according to claim 3, characterized in that, The inoculation amount of the *Serratia marcescens* strain BJ827 is 1% (v / v) to 5% (v / v).

5. The application according to claim 3, characterized in that, The pH of the cadmium-contaminated water body to be remediated is 5–9.

6. The application according to claim 3, characterized in that, The cultivation in S2 is carried out in a shaker at 30℃ to 44℃ for 12 h to 96 h.

7. The application according to claim 6, characterized in that, The shaking incubator rotates at a speed of 80 rpm to 160 rpm.

8. The application according to any one of claims 3 to 7, characterized in that, The application method is as follows: S1. After activating the Serratia marcescens strain BJ827, culture it to the logarithmic phase; S2. Inoculate into the cadmium-contaminated water body to be remediated, adjust the pH to neutral, and incubate at 30℃ with a shaker at 120 rpm for 96 h to achieve in-situ remediation of the cadmium-contaminated environment.

9. The application of the spider gut-derived, highly cadmium-resistant Serratia marcescens according to claim 1 in the preparation of a biosorbent for adsorbing cadmium, characterized in that, The application is as follows: Serratia marcescens strain BJ827 is combined with a carrier material to prepare a biosorbent, wherein the carrier is one of diatomaceous earth, activated carbon, sodium alginate gel and polyacrylamide.

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