Probiotics Pediococcus acidilactici GR-1 promotes the functional strains and remodels gut microbiota to reduce the Cr(VI) toxicity in a dual-chamber simulated intestinal system.

Numerous animal studies have demonstrated the toxicity of hexavalent chromium [Cr(VI)] and the bioremediative effects of probiotics on the composition and functions of gut microbiota. Since the precise mechanisms of Cr(VI) detoxification and its interactions with human gut microbiota were unknown, a novel dual-chamber simulated intestinal (DCSI) system was developed to maintain both the stability of the simulated system and the composition of the gut microbiota. Probiotic GR-1 was found to regulate intestinal gut microbiota, thereby reducing the toxicity of Cr(VI) within the DCSI system. The results indicate that Cr(VI) levels were reduced from 2.260 ± 0.2438 µg/g to 1.7086 ± 0.1950 µg/g in the gut microbiota cell pellet, and Cr(VI) permeability decreased from 0.5521 ± 0.1132 µg/L to 0.3681 ± 0.0178 µg/L after 48 h in simulated gut fluid. Additionally, the removal rate of 1,1-Diphenyl-2-picrylhydrazyl (DPPH), reducibility (Vitamin C), and total antioxidant capacity (T-AOC) increased by 50.83%, 31.70%, and 27.56%, respectively, following probiotic treatment. The increase in antioxidant capacity correlated with total Cr removal (P < 0.05, r from -0.80 to 0.73). 16S rRNA sequencing analysis showed that gut microbiota composition was reshaped by the addition of probiotics, which regulated the recovery of the functional gut microbiota to normal levels, rather than restoring the entire gut microbiota composition for community function. Thus, this study not only demonstrates the feasibility and stability of culturing gut microbiota but also offers a new biotechnological approach to synthesizing functional communities with functional strains for environmental risk management.

Fermented lily bulbs by "Jiangshui" probiotics improves lung health in mice.

Limited application in protecting lung health is attributed to the low levels of active compounds in lily plant bulbs. This study focused on enhancing the active compounds by fermenting Lilium davidii (Lanzhou Lily) bulbs with Limosilactobacillus fermentum GR-3, isolated from Jiangshui. Lily fermented bulbs with strain GR-3 (LFB+GR-3) increased the bioavailability of hexadecanoic acid methyl ester, 22-tetrahydroxy-5alpha-cholestan-6-one-3-O-beta-d-allopyranoside, 22-O-(6-deoxy-Alpha-l-mannopyranosyl)-3-O-beta-d-glucopyranosyl-pregn-5-en-20-one, 1-O-trans-feruloylglycerol, and 3,4 dihydroxybenzoic acid. LFB+GR-3 fraction was employed to treat the mice model exposed to the carbon black nanoparticles (CBNPs). Immunohistochemical analysis revealed that the deposition of CBNPs and damages in lung tissues were limited in the LFB+GR-3 treatment group, while TNF-α, IL-10, and IL-6 were elevated by 6.9, 4.3, and 7 folds in the CBNP exposure group. In addition, Lactobacillus, Escherichia, Lactococcus, and Muribacter were dominant in the lung microbiota of LFB+GR-3 than the CBNP group. The use of probiotic fermented lily bulbs might be helpful in lung infection treatment.

Gut microbes consume host energy and reciprocally provide beneficial factors to sustain a symbiotic relationship with the host.

The gut microbes thrive by utilizing host energy and, in return, provide valuable benefits, akin to the symbiotic relationship. To study the mutualistic association between the gut microbiota and host, a range of gut microbe populations (85 %, 66 %, 45 % and 38 % at the normal level) with comparable structures were constructed in broiler model. The results revealed that reductions in gut microbial population led to decreased energy consumption, resulting in increased host weight (10.26 %, 30.88 %, 17.65 % and - 12.77 %, respectively). Fecal metabolome revealed that among 85 % and 66 % of the normal population level, the gut microbes downregulated the immune-associated pathways of tryptophan metabolism and catecholamine biosynthesis, while the level of fatty acid oxidation was upregulated at 45 %. In the host, the concentration of gut microbes contributed to regulate functions related to lipid biosynthesis (from glycerophosphoserines to glycerophosphoethanolamines (9.63 %, 12.20 %, 6.66 % and 47.75 %) and glycerophosphocholines (10.78 %, 36.51 %, 2.00 % and 87.11 %)) and inflammation responses (methionine and betaine metabolism). From 85 % to 45 % of gut microbes, broiler showed an inhibited immunity (thymus gland, spleen, SIgG and IgA) and increased low-level inflammation response (ALT and T-SOD). However, at 38 %, the immune indexes exhibited an increase (thymus gland, spleen, SIgG, and IgA increased by 8.67 %, 8.50 %, 20.87 %, and 29.43 %, respectively), indicating the host lipid accumulation and inflammation response were negatively correlated with the immune reaction. Collectively, the gut microbiota maintains a symbiotic relationship with the host through the secretion of beneficial substances to interact with the host.

A gluten degrading probiotic Bacillus subtilis LZU-GM relieve adverse effect of gluten additive food and balances gut microbiota in mice.

Gluten accumulation damages the proximal small intestine and causes celiac disease (CeD) which has not been effectively treated except by using a gluten-free diet. In this study, strain Bacillus subtilis LZU-GM was isolated from Pakistani traditional fermented sourdough and could degrade 73.7% of gluten in 24 h in vitro. Strain LZU-GM was employed for practical application to investigate gluten degradation in mice models. The results showed that strain LZU-GM was colonized in mice and the survival rate was around 0.95 % (P < 0.0001). The gluten degradation was 3-fold higher in the small intestine of the strain LZU-GM treated mice group remaining 1511.96 ng/mL of gluten peptides than the untreated mice group (6500.38 ng/mL). Immunochemical analysis showed that gluten-treated mice established positive antigliadin antibodies (AGA) in serum (IgA, IgG, and anti-TG2 antibodies) as compared to the strain LZU-GM treatment group. Furthermore, the number of IFN-γ, TNF-α, IL-10, and COX-2 cells decrease in the lamina propria of the strain LZU-GM treatment group (P < 0.0001). Microbial community bar plot analysis showed that Lactobacillus, Dubosiella, and Enterococcus genera were restored and stabilized in the LZU-GM treatment group while Blautia and Ruminococcus were found lower. The oral gavage of probiotic strain LZU-GM might be useful for gluten metabolism in the intestine during digestion and would be a long-term dietary treatment for CeD management.

Nickel exposure induces gut microbiome disorder and serum uric acid elevation.

Serum uric acid elevation has been found in long-term nickel (Ni) exposure occupational workers, but the mechanism is unclear. In this study, the relationship between Ni exposure and uric acid elevation was explored in a cohort of 109 participants composed of a Ni-exposed workers group and a control group. The results showed that Ni concentration (5.70 ± 3.21 µg/L) and uric acid level (355.95 ± 67.87 µmol/L) in the serum were increased in the exposure group with a significant positive correlation (r = 0.413, p < 0.0001). The composition of gut microbiota and metabolome revealed that the abundance of uric acid-lowering bacteria, such as Lactobacillus, Lachnospiraceae_Unclassfied and Blautia were reduced while pathogenic bacteria including Parabacteriadies and Escherichia-Shigella were enriched in Ni group, accompanied by impaired intestinal degradation of purines and upregulated biosynthesis of primary bile acids. Consistent with human results, the mice experiments showed that Ni treatment significantly promotes uric acid elevation and systemic inflammation. Lactobacillus and Blautia in gut microbiota were reduced and inflammation-related taxa Alistipes and Mycoplasma were enriched in the Ni treatment. In addition, LC-MS/MS metabolomic analysis indicated that purine nucleosides were accumulated in mice feces, which increased purine absorption and uric acid elevation in the serum. In summary, this study provides evidence that UA elevation was correlated with heavy metals exposure and highlighted the role of gut microbiota in intestinal purine catabolism and in the pathogenesis of heavy metal-induced hyperuricemia.

Human supplementation with Pediococcus acidilactici GR-1 decreases heavy metals levels through modifying the gut microbiota and metabolome.

Exposure to heavy metals (HMs) is a threat to human health. Although probiotics can detoxify HMs in animals, their effectiveness and mechanism of action in humans have not been studied well. Therefore, we conducted this randomized, double-blind, controlled trial on 152 occupational workers from the metal industry, an at-risk human population, to explore the effectiveness of probiotic yogurt in reducing HM levels. Participants were randomly assigned to two groups: one consumed probiotic yogurt containing the HM-resistant strain Pediococcus acidilactici GR-1 and the other consumed conventional yogurt for 12 weeks. Analysis of metal contents in the blood revealed that the consumption of probiotic yogurt resulted in a higher and faster decrease in copper (34.45%) and nickel (38.34%) levels in the blood than the consumption of conventional yogurt (16.41% and 27.57%, respectively). Metagenomic and metabolomic studies identified a close correlation between gut microbiota (GM) and host metabolism. Significantly enriched members of Blautia and Bifidobacterium correlated positively with the antioxidant capacities of GM and host. Further murine experiments confirmed the essential role of GM and protective effect of GR-1 on the antioxidative role of the intestine against copper. Thus, the use of probiotic yogurt may be an effective and affordable approach for combating toxic metal exposure through the protection of indigenous GM in humans.ClinicalTrials.gov identifier: ChiCTR2100053222.

Feed-additive Limosilactobacillus fermentum GR-3 reduces arsenic accumulation in Procambarus clarkii.

Procambarus clarkii (crayfish) accumulates a high concentration of Arsenic (As) from the aquatic environment and causes considerable human health risks. In this study, Limosilactobacillus fermentum GR-3 strain was isolated from "Jiangshui" and applied for As(III) adsorption and antioxidant abilities. Strain GR-3 removed 50.67% of 50 mg/L As(III) and exhibited the high antioxidant potential of DPPH (1,1-Diphenyl-2-picrylhydrazyl) (87.63%) and hydroxyl radical (74.51%) scavenging rate in vitro. P. clarkii was feed with strain GR-3, the results showed that As(III) concentration reduced, and residual level in hepatopancreas was decreased by 36%, compared to As(III)-exposed group (control). Gut microbial sequencing showed that strain GR-3 restores gut microbiota dysbiosis caused by As(III) exposure. Further application in the field scale was performed and revealed a decrease in As(III) accumulation and increasing 50% aquaculture production of the total output. In summary, feed-additive probiotic is recommended as a novel strategy to minimize aquaculture foods toxicity and safe human health.

Protein biomethanation: insight into the microbial nexus.

Biomethanation of carbohydrates (e.g., lignocellulosic biomass) and lipids (e.g., waste oils) has been well studied. However, investigations on the biomethanation of protein-rich biowastes (PRBs) and associated microbial communities have not been reported. This review summarizes the challenges in the metabolic process of anaerobic digestion of PRBs and the microbial instability associated with it. We discuss the diversity of bacterial and archaeal communities via metagenomics under PRB mono- and codigestion. A stable community structure with enhanced metabolic activity is a core factor in PRB biomethanation. The application of strategies such as codigestion of PRBs with carbon-rich biomass and microbial stimulation/augmentation would make PRB biomethanation more feasible.

Chitooligosaccharides production from shrimp chaff in chitosanase cell surface display system.

Chitin refers to a natural biopolymer, which is economically significant to next-generation biorefineries. In this study, a novel high-yield method with cell surface-display chitosanase (CHI-1) was built to produce chitooligosaccharides (COS) from shrimp chaff through the co-fermentation in the presence of Bacillus subtilis and Acetobacter sp. Under the optimized co-fermentation conditions (5 g/L yeast extracts, 10 g/L KH2PO4, 6% ethanol, 50 g/L glucose), the final deproteinization (DP) and demineralization (DM) efficiency and the chitin yield were achieved as 94, 92 and 18%, respectively. The engineered E. coli BL21-pET23b(+)-NICHI maintained 81% of the initial enzyme activity after 40 days at room temperature. The crude CHI-1 was inactivated after one-day interacting with prepared chitosan. Moreover, E. coli BL21-pET23b(+)-NICHI still maintained excellent hydrolysis ability in 7 days, and the COS yield reached 41%. Accordingly, the proposed method exhibited excellent stability and a high hydrolysis efficiency to produce COS with whole engineered cells.

Bioaugmentation improves the anaerobic co-digestion of cadmium-containing plant residues and cow manure.

Phytoremediation causes a large quantity of phytoremediation residues rich in heavy metals (HMs). This kind of plant residue can be used as a substrate for anaerobic digestion (AD) to reduce the content of HM-containing biomass, but high concentrations of HMs will inhibit the digestion efficiency and reduce the conversion efficiency of plant residues. Bioaugmentation may be an effective method to improve the degradation efficiency and methane yield of plant residues rich in HMs. In this study, a cellulose-degrading anaerobic bacteria Paracoccus sp. Termed strain LZ-G1 was isolated from cow dung, which can degrade cellulose and simultaneously adsorb Cd2+. The Cd2+ (10 mg/L)-adsorbtion efficiency and cellulose (463.12 g/kg)-degradation rate were 65.1 % and 60.59 %, respectively. In addition, using the strain LZ-G1 bioaugmented Cd2+-containing plant residues and cow manure mixed AD system, the system's biogas and methane production significantly increased (98.97 % and 142.03 %, respectively). During the AD process, the strain LZ-G1 was successfully colonized in the digestion system. Furthermore, the microbial community analysis revealed that LZ-G1 bioaugmentation alleviates the toxicity of free Cd2+ to the microbial community in the AD system, regulates and restores the archaea genus dominant in the methanogenesis stage, and restores the relative abundance of dominant bacteria associated with biomass hydrolysis. The restoration of the microbial community increased the biogas yield and methane production rate. Thus, bioaugmentation provides an easy and a feasible method for the actual on-site treatment of HM-rich phytoremediation residues.

Biomethanation and microbial community response during agricultural biomass and shrimp chaff digestion.

Anaerobic digestion, a promising technology for waste utilization and bioenergy generation, is a suitable approach to convert the shrimp waste to biomethane, reducing its environmental impact. In this study, shrimp chaff (SC) was co-digested corn straw (CS), wheat straw (WS), and sugarcane bagasse (SB). In co-digestion, SC enhanced biomethane production of CS by 8.47-fold, followed by SC + WS (5.67-folds), and SC + SB (3.37-folds). SC addition to agricultural biomass digestion also promoted the volatile solids removal up to 85%. Microbial community analysis of SC and CS co-digestion presented the dominance of phylum Bacteroidetes, Firmicutes, Proteobacteria, and Euryarchaeota. Proteolytic bacteria were dominant (18.02%) during co-digestion of SC and CS, with Proteiniphilum as major bacterial genera (14%) that converts complex proteinaceous substrates to organic acids. Among the archaeal community, Methanosarcina responsible for conversion of acetate and hydrogen to biomethane, increased up to 70.77% in SC and CS digestion. Addition of SC to the digestion of agricultural wastes can significantly improve the biomethane production along with its effective management to reduce environmental risks.

Gut Escherichia coli expressing Pb2+-adsorption protein reduces lead accumulation in grass carp, Ctenopharyngodon idellus.

Lead (Pb2+) is easy to accumulate in fish which become a major source of Pb2+ exposure to humans. In this study, a recombinant Escherichia coli strain expressing Pb2+-specific surface-binding protein anchored by the ice nucleation protein was introduced into grass carp (Ctenopharyngodon idellus) gut to investigate its protective effect against dietary Pb2+ exposure. Pb2+ mostly precipitated on the surface of the engineered strain through Pb2+-specific surface-binding protein, with a maximum adsorption efficiency of 73% and an adsorption capacity of 163 µmol/g dry cells. The Pb2+ concentration in engineered bacteria-fed grass carp was reduced significantly, and the residual level of Pb2+ in feces was increased by 76%, compared with the control group. Meantime, the engineered bacteria were able to mitigate the oxidative stress and histological alterations of intestines and dysbiosis of gut microbiota induced by Pb2+exposure. Thus, the engineered bacterium that can effectively reduce Pb2+ residue in grass carp might be a useful tool for decontamintion of lead in aquatic organisms.

Feed-additive of bioengineering strain with surface-displayed laccase degrades sulfadiazine in broiler manure and maintains intestinal flora structure.

Sulfonamide antibiotics (SAs) are excreted into the ecosystem unchanged through feces and urine because of their low adsorption and degradation in the guts of humans and animals. In this study, a novel whole-cell biocatalyst with fungal laccase on the cell surface of Escherichia coli Nissle 1917 was developed to degrade sulfadiazine (SDZ). Engineered strain EcN-IL showed laccase enzyme activity of 2 ± 1 U/mg dry weight of cell and degraded 37 ± 1% of SDZ at temperature 40 °C and pH 5 within 3 h in vitro. Strain EcN-IL with 500 mg/kg of SDZ was employed as a food supplement to feed chicken broilers, which can reduce the residue of SDZ in broiler manure by 58 ± 2% and also reduced dysbiosis of the gut microbiota due to overuse of antibiotics. The genetically engineered EcN-IL has laid a foundation for degrading SDZ in broilers and their manure.

The guanidine thiocyanate-high EDTA method for total microbial RNA extraction from severely heavy metal-contaminated soils.

Molecular analyses relying on RNA, as a direct way to unravel active microbes and their functional genes, have received increasing attention from environmental researchers recently. However, extracting sufficient and high-quality total microbial RNA from seriously heavy metal-contaminated soils is still a challenge. In this study, the guanidine thiocyanate-high EDTA (GTHE) method was established and optimized for recovering high quantity and quality of RNA from long-term heavy metal-contaminated soils. Due to the low microbial biomass in the soils, we combined multiple strong denaturants and intense mechanical lysis to break cells for increasing RNA yields. To minimize RNAase and heavy metals interference on RNA integrity, the concentrations of guanidine thiocyanate and EDTA were increased from 0.5 to 0.625 ml g-1 soil and 10 to 100 mM, respectively. This optimized GTHE method was applied to seven severely contaminated soils, and the RNA recovery efficiencies were 2.80 ~ 59.41 µg g-1 soil. The total microbial RNA of non-Cr(VI) (NT) and Cr(VI)-treated (CT) samples was utilized for molecular analyses. The result of qRT-PCR demonstrated that the expressions of two tested genes, chrA and yieF, were respectively upregulated 4.12- and 62.43-fold after Cr(VI) treatment. The total microbial RNA extracted from NT and CT samples, respectively, reached to 26.70 µg and 30.75 µg, which were much higher than the required amount (5 µg) for metatranscriptomic library construction. Besides, ratios of mRNA read were more than 86%, which indicated the high-quality libraries constructed for metatranscriptomic analysis. In summary, the GTHE method is useful to study microbes of contaminated habitats.

Exploring novel Cr(VI) remediation genes for Cr(VI)-contaminated industrial wastewater treatment by comparative metatranscriptomics and metagenomics.

Microbial remediation is a promising method to treat Cr(VI) in industrial wastewater. The remediation efficiency and stress-resistance ability of Cr(VI) remediation genes in microbes are the limiting factors for their application in industrial wastewater treatment. To screen novel highly efficient Cr(VI) remediation genes, comparative metatranscriptomic and metagenomic analyses were performed on long-term Cr(VI)-contaminated riparian soil with/without additional Cr(VI) treatment. The most suitable Cr(VI) treatment time was determined to be 30 min according to the high quality RNA yield and fold changes in gene expression. Six novel genes, which had complete open reading frames (ORFs) in metagenomic libraries, were identified from unculturable microbes. In the phenotypic functional assay, all novel genes enhanced the Cr(VI) resistance/reduction ability of E. coli. In the industrial wastewater treatment, E-mcr and E-gsr presented at least 50% Cr(VI) removal efficiencies in the presence of 200-600 µM of Cr(VI), without a decrease in efficiency over 17 days. The stress resistance assay showed that gsr increased the growth rate of E. coli by at least 30% under different extreme conditions, and thus, gsr was identified as a general stress-response gene. In the Cr valence distribution assay, E-mcr presented ~40 µM higher extracellular Cr (III) compared to E-yieF. Additionally, transmission electron microscopy (TEM) of E-mcr showed bulk black agglomerates on the cell surface. Thus, mcr was identified as a membrane chromate reductase gene. This research provides a new idea for studying novel highly efficient contaminant remediation genes from unculturable microbes.

Tibet plateau probiotic mitigates chromate toxicity in mice by alleviating oxidative stress in gut microbiota.

Heavy metal contamination in food endangers human health. Probiotics can protect animals and human against heavy metals, but the detoxification mechanism has not been fully clarified. Here, mice were supplemented with Pediococcus acidilactici strain BT36 isolated from Tibetan plateau yogurt, with strong antioxidant activity but no chromate reduction ability for 20 days to ensure gut colonization. Strain BT36 decreased chromate accumulation, reduced oxidative stress, and attenuated histological damage in the liver of mice. 16S rRNA and metatranscriptome sequencing analysis of fecal microbiota showed that BT36 reversed Cr(VI)-induced changes in gut microbial composition and metabolic activity. Specifically, BT36 recovered the expressions of 788 genes, including 34 inherent Cr remediation-relevant genes. Functional analysis of 10 unannotated genes regulated by BT36 suggested the existence of a new Cr(VI)-reduction gene in the gut microbiota. Thus, BT36 can modulate the gut microbiota in response to Cr(VI) induced oxidative stress and protect against Cr toxicity.

A novel biosensor for zinc detection based on microbial fuel cell system.

Microbial fuel cell (MFC) biosensors are self-sustainable device for monitoring of various substrates; however, for heavy metals detection are still scarce. In this study, E. coli BL21 was engineered to express the zntR, ribB, and oprF genes with PzntA promoter, which could sense zinc (Zn2+) for riboflavin and porin production. The engineered strain produced high levels of riboflavin (2.4-3.6 µM) and improved cell membrane permeability, with a positive correlation of Zn2+ (0-400 µM). The strain was then employed in MFC biosensor under the following operational parameters: external resistance 1000 Ω, pH 9, and temperature 37 °C for Zn2+ sensing. The maximum voltages (160, 183, 260, 292, and 342 mV) of the constructed MFC biosensor have a linear relationship with Zn2+ concentrations (0, 100, 200, 300, and 400 µM, respectively) (R2 = 0.9777). An Android App was developed for the biosensor system that could sense Zn2+ in real-time and in situ. The biosensor was applied to wastewater with different Zn2+ concentrations and the results showed that the detection range for Zn2+ was 20-100 µM, which covers common Zn2+ safety standards. The results obtained with developed MFC biosensor were comparable to conventional methods such as colorimetric, flame atomic absorption spectroscopy (FAAS), and inductively coupled plasma optical emission spectroscopy (ICP-OES). In summary, MFC biosensor with biosynthetic strain is an efficient and affordable system for real-time monitoring and sensing of heavy metals.

Micro-aeration in anode chamber promotes p-nitrophenol degradation and electricity generation in microbial fuel cell.

Biodegradation of recalcitrant organic compounds in microbial fuel cell (MFC) is limited, due to its strong electron affinity and persisted in anaerobic condition. In this study, Pseudomonas monteilii LZU-3 degraded p-nitrophenol (PNP) and generated current at 100 mg L-1 of PNP in anode MFC with the addition of oxygen. The highest PNP degradation was 4, 37.75, and 99.89% in anaerobic, aerobic, and aerated anode of MFC respectively, at 7 h. The maximum voltage generation in aerated anode was 183 mV, which was comparatively higher than aerobic (150 mV) and anaerobic (68 mV). The qRT-PCR results confirmed that the oxygenase genes in strain LZU-3 were up-regulated from 17.51 to 39.39-fold at 1.6-4.5 mg L-1 of oxygen concentrations resulted in PNP degradation in anode MFC. This study demonstrated that supplementation of oxygen into the anode MFC might be a potential approach for biodegradation of recalcitrant compounds and electricity generation.

Improvements of thermophilic enzymes: From genetic modifications to applications.

Thermozymes (from thermophiles or hyperthermophiles) offer obvious advantages due to their excellent thermostability, broad pH adaptation, and hydrolysis ability, resulting in diverse industrial applications including food, paper, and textile processing, biofuel production. However, natural thermozymes with low yield and poor adaptability severely hinder their large-scale applications. Extensive studies demonstrated that using genetic modifications such as directed evolution, semi-rational design, and rational design, expression regulations and chemical modifications effectively improved enzyme's yield, thermostability and catalytic efficiency. However, mechanism-based techniques for thermozymes improvements and applications need more attention. In this review, stabilizing mechanisms of thermozymes are summarized for thermozymes improvements, and these improved thermozymes eventually have large-scale industrial applications.

Reducing methylmercury accumulation in fish using Escherichia coli with surface-displayed methylmercury-binding peptides.

Seafood consumption is widely considered as the primary route for human exposure to the neurotoxin methylmercury (MeHg) that is produced by certain anaerobic microorganisms and can bioaccumulate to high concentration levels in natural aquatic food webs. In this study, a novel methylmercury-binding peptide with seven amino acids was displayed on the cell surfaces of Escherichia coli strain W-1, which was isolated from fish feces and fused with ice nucleation protein. These cells exhibited high affinity and selectivity toward methylmercury. They efficiently removed more than 96% of 12 µM methylmercury, and accumulation of methylmercury in the engineered strain was four times higher than that in the wild type. Transmission electron microscopy confirmed methylmercury accumulation on cell membranes. Carassius auratus was fed by engineered bacteria, which showed a decrease in methylmercury concentration in muscles of about 36.3 ± 0.7%; whereas an increase in methylmercury concentration was observed in the feces (36.7 ± 0.8%) in comparison to the control group. The engineered strain in the gut captured methylmercury and prevented it's absorption by muscles, while some bacteria with methylmercury were excreted in the feces. The surface-engineered E. coli effectively protected fish from methylmercury contamination.