Antioxidant activity changes of exopolysaccharides with different carbon sources from Lactobacillus plantarum LPC-1 and its metabolomic analysis

Transcriptome Analysis Reveals the Role of Sucrose in the Production of Latilactobacillus sakei L3 Exopolysaccharide

Latilactobacillus (L.) sakei is a species of lactic acid bacteria (LAB) mostly studied according to its application in food fermentation. Previously, L. sakei L3 was isolated by our laboratory and possessed the capability of high exopolysaccharide (EPS) yield during sucrose-added fermentation. However, the understanding of sucrose promoting EPS production is still limited. Here, we analyzed the growth characteristics of L. sakei L3 and alterations of its transcriptional profiles during sucrose-added fermentation. The results showed that L. sakei L3 could survive between pH 4.0 and pH 9.0, tolerant to NaCl (<10%, w/v) and urea (<6%, w/v). Meanwhile, transcriptomic analysis showed that a total of 426 differentially expressed genes and eight non-coding RNAs were identified. Genes associated with sucrose metabolism were significantly induced, so L. sakei L3 increased the utilization of sucrose to produce EPS, while genes related to uridine monophosphate (UMP), fatty acids and folate synthetic pathways were significantly inhibited, indicating that L. sakei L3 decreased self-growth, substance and energy metabolism to satisfy EPS production. Overall, transcriptome analysis provided valuable insights into the mechanisms by which L. sakei L3 utilizes sucrose for EPS biosynthesis. The study provided a theoretical foundation for the further application of functional EPS in the food industry.

Exploration of Exopolysaccharide from Leuconostoc mesenteroides HDE-8: Unveiling Structure, Bioactivity, and Food Industry Applications

A strain of Leuconostoc mesenteroides HDE-8 was isolated from homemade longan fermentation broth. The exopolysaccharide (EPS) yield of the strain was 25.1 g/L. The EPS was isolated and purified, and the structure was characterized using various techniques, including X-ray diffraction (XRD), nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, high-performance size exclusion chromatography (HPSEC), and scanning electron microscopy (SEM). The monosaccharide composition of the EPS was glucose, with a molecular weight (Mw) of 1.7 × 106 Da. NMR spectroscopy revealed that the composition of the HDE-8 EPS consisted of D-glucose pyranose linked by α-(1→4) and α-(1→6) bonds. The SEM analysis of the EPS showed an irregular sheet-like structure. Physicochemical analysis demonstrated that EPSs exhibit excellent thermal stability and high viscosity, making them suitable for fermentation in heat-processed and acidic foods. Additionally, milk coagulation tests showed that the presence of EPSs promotes milk coagulation when supplemented with sucrose. It suggests that EPSs have wide-ranging potential applications as food additives, improving the texture and taste of dairy products. This study provides practical guidance for the commercial use of HDE-8 EPSs in the food and related industries.

Genomic and transcriptomic analysis of genes involved in exopolysaccharide biosynthesis by Streptococcus thermophilus IMAU20561 grown on different sources of nitrogen

Exopolysaccharides (EPSs), which are produced by lactic acid bacteria, have been found to improve the texture and functionality of fermented dairy products. In a previous study, four nitrogen sources were identified as affecting the yield, molecular weight and structure of EPSs produced by Streptococcus thermophilus IMAU20561 in M17 medium. In this genomic and transcriptomics study, a novel eps gene cluster responsible for assembly of repeating units of EPS is reported. This eps cluster (22.3 kb), consisting of 24 open reading frames, is located in the chromosomal DNA. To explore the biosynthetic mechanisms in EPS, we completed RNA-seq analysis of S. thermophilus IMAU20561 grown in four different nitrogen sources for 5 h (log phase) or 10 h (stationary phase). GO functional annotation showed that there was a significant enrichment of differentially expressed genes (DEGs) involved in: amino acid biosynthesis and metabolism; ribonucleotide biosynthesis and metabolism; IMP biosynthesis and metabolism; and phosphorus metabolism. KEGG functional annotation also indicated enrichment of DEGs involved in amino acid biosynthesis, glycolysis, phosphotransferase system, fructose, and mannose metabolism. Our findings provide a better understanding the genetic traits of S. thermophilus, the biosynthetic pathways needed for the production of EPS, and a theoretical basis for screening dairy starter cultures.

Exploring the mechanism of exopolysaccharides in mitigating cadmium toxicity in rice through analyzing the changes of antioxidant system

Recently, exopolysaccharides (EPS) were found to alleviate cadmium (Cd) toxicity to crops by regulating the antioxidant system, but the mechanism remains unclear. Herein, by quantitative and transcriptomic approaches, a systematical map of the changes in the antioxidant system was drawn to dissected the underlying mechanism. The results demonstrated that the ascorbate-glutathione cycle (ASA-GSH cycle) is a major contributor. Specifically, compared to the control, the rice exposed to Cd exhibited a significant increase in the GSH pool (about 9-fold at 7 d), but a continuous decrease in the ASA pool (only 15.42% remained at 15 d) and an excessive accumulation of reactive oxygen species (ROS). Interestingly, with the addition of EPS, the increase of the GSH pool significantly slowed down (decreased by 180.18% at 7 d, compared to the Cd-stressed treatment), and the ASA pool remained high (consistently above 70.00% of the control group). ROS also maintained at a good level. Moreover, the activities of enzymatic antioxidants showed the similar trend. By RNA-Seq analysis, multiple genes enriched in ASA-GSH related pathway were screened (such as OsRBOHB, OsGST, OsPOD) for further study. This study provides a foundation for EPS application in agriculture, which also establishes a better way for analyzing antioxidant system.

Effects of Nutrients on the Growth of and Free Exopolysaccharide Biosynthesis by Streptococcus thermophilus 937 in a Chemically Defined Medium

The free exopolysaccharide (f-EPS) produced by Streptococcus thermophilus is a natural texture modifier with health-promoting properties and has thus become one of the most interesting metabolites for researchers. The present work aimed to further understand the nutritional requirements for the growth of and the f-EPS production by S. thermophilus. The types and concentrations of compounds in the complete chemically defined medium were changed in turn to evaluate the effects of single nutrients on the growth of and f-EPS production by S. thermophilus 937. The results showed that cysteine, glutamine, histidine, methionine, tryptophan, tyrosine, leucine, isoleucine, and valine played an important role in maintaining the rapid and stable growth of S. thermophilus 937. S. thermophilus 937 also required calcium pantothenate, niacin, pyridoxine, riboflavin, and thiamine hydrochloride as essential nutrients for growth. Increases in the concentrations of lactose, glutamate, histidine, or isoleucine significantly increased the production of free exopolysaccharide by S. thermophilus 937, and when the lactose concentration increased to 20 g·L-1 and the concentration of the three-amino-acid combination increased to 15 mM, the f-EPS yield increased to a maximum of 35.34 μg·mL-1. This finding indicated that lactose and the 3 amino acids exert synergistic effects on the promotion of f-EPS production. In addition, lactose and the three amino acids have strain specific promoting effects on f-EPS production by S. thermophilus. This study provides a further understanding of the effects of nutrients on the biosynthesis of f-EPS by S. thermophilus.

Optimization of Exopolysaccharide Produced by Lactobacillus plantarum R301 and Its Antioxidant and Anti-Inflammatory Activities

In this study, the yield of exopolysaccharide (EPS) from Lactobacillus plantarum R301 was optimized using a single-factor experiment and response surface methodology (RSM). After optimization, the EPS yield was increased with a fold-change of 0.85. The significant factors affecting EPS production, as determined through a Plackett-Burman design and Central Composite Design (CCD), were MgSO₄ concentration, initial pH, and inoculation size. The maximum yield was 97.85 mg/mL under the condition of 0.01% MgSO₄, an initial pH 7.4, and 6.4% of the inoculation size. In addition, the EPS exhibited strong antioxidant activity, as demonstrated by its ability to scavenge DPPH, ABTS, and hydroxyl radicals. The scavenging rate was up to 100% at concentrations of 4 mg/mL, 1 mg/mL, and 2 mg/mL, respectively. Moreover, the EPS also exhibited reducing power, which was about 30% that of ascorbic acid when both tended to be stable with the increased concentration. These results suggest that L. plantarum R301 EPS possesses different antioxidant mechanisms and warrants further investigation. In addition to its antioxidant activity, the EPS also demonstrated good anti-inflammatory activity by inhibiting the inflammation induced by lipopolysaccharide (LPS) in RAW 264.7 cells, which could decrease nitric oxide (NO) production and expression of the proinflammatory cytokine Il-6. These findings suggest that L. plantarum R301 EPS could be used as a potential multifunctional food additive in the food industry.

Mycelial biomass and intracellular polysaccharides production, characterization, and activities in Auricularia auricula-judae cultured with different carbon sources

The carbon source, an essential factor for submerged culture, affects fungal polysaccharides production, structures, and activities. This study investigated the impact of carbon sources, including glucose, fructose, sucrose, and mannose, on mycelial biomass and the production, structural characterization, and bioactivities of intracellular polysaccharides (IPS) produced by submerged culture of Auricularia auricula-judae. Results showed that mycelial biomass and IPS production varied with different carbon sources, where using glucose as the carbon source produced the highest mycelial biomass (17.22 ± 0.29 g/L) and IPS (1.62 ± 0.04 g/L). Additionally, carbon sources were found to affect the molecular weight (Mw) distributions, monosaccharide compositions, structural characterization, and activities of IPSs. IPS produced with glucose as the carbon source exhibited the best in vitro antioxidant activities and had the strongest protection against alloxan-damaged islet cells. Correlation analysis revealed that Mw correlated positively with mycelial biomass (r = 0.97) and IPS yield (r = 1.00), while IPS antioxidant activities correlated positively with Mw and negatively with mannose content; the protective activity of IPS was positively related to its reducing power. These findings indicate a critical structure-function relationship for IPS and lay the foundation for utilizing liquid-fermented A. aruicula-judae mycelia and the IPS in functional food production.

Microbial extracellular polymeric substances alleviate cadmium toxicity in rice (Oryza sativa L.) by regulating cadmium uptake, subcellular distribution and triggering the expression of stress-related genes

Cadmium (Cd) accumulation in crops causes potential risks to human health. Microbial extracellular polymeric substances (EPS) are a complex mixture of biopolymers that can bind various heavy metals. The present work examined the alleviating effects of EPS on Cd toxicity in rice and its detoxification mechanism. The 100 μM Cd stress hampered the overall plant growth and development, damaged the ultrastructures of both leaf and root cells, and caused severe lipid peroxidation in rice plants. However, applying EPS at a concentration of 100 mg/L during Cd stress resulted in increased biomass, reduced Cd accumulation and transport, and minimized the oxidative damage. EPS application also enhanced Cd retention in the shoot cell walls and root vacuoles, and actively altered the expression of genes involved in cell wall formation, antioxidant defense systems, transcription factors, and hormone metabolism. These findings provide new insights into EPS-mediated mitigation of Cd stress in plants and help us to develop strategies to improve crop yield in Cd-contaminated soils in the future.

Extraction and characterization of exopolysaccharides from Lactiplantibacillus plantarum strain PRK7 and PRK 11, and evaluation of their antioxidant, emulsion, and antibiofilm activities

Exopolysaccharides (EPS) are produced by probiotic bacteria Lactiplantibacillus plantarum PRK7 and L. plantarum PRK11. The structure of EPS-7 and EPS-11 was characterized by Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), gas chromatography-mass spectroscopy (GCMS), and thermogravimetric analysis (TGA). Further, in in vitro studies antioxidant, emulsion, and antibiofilm activity were investigated. The FTIR spectrum confirmed the presence of polysaccharides in EPS-7 and EPS-11, with absorbance at 1654.93 and 1655.33 cm^-1, respectively. H¹ NMR further confirmed the presence of glucose, galactose, xylose, and mannose. Sugar derivatives in EPS-7 and EPS-11 were further confirmed with GCMS. The SEM analysis revealed that EPS-7 had a weblike structure and EPS-11 had a smooth porous layer. The result of the TGA revealed that EPS-7 and EPS-11 had greater thermal stability at 319.1 and 300.1 °C, respectively. Furthermore, EPS-7 and EPS-11 showed a good percentage of free radical scavenging in DPPH (89.77 % and 93.1 %), ABTS (57.65 % and 58.63 %), hydroxyl radical scavenging (44.46 % and 40.308 %), and reducing power assay. The emulsion activity was confirmed with edible oils such as coconut oil, sesame oil, almond oil, castor oil, and neem oil. The highest emulsion activity for EPS-7 and EPS-11 was found be with coconut and castor oil. In addition, the antibiofilm activity against pathogens revealed that EPS possess can prevent biofilm formation. Thus, it was found that EPS-7 and EPS-11 possess good structural characteristics and their biological activity makes them ideal for applications in the food and pharmaceutical industry.

Root cell wall remodeling: A way for exopolysaccharides to mitigate cadmium toxicity in rice seedling

Exopolysaccharides (EPS) are macromolecules with environment beneficial properties. Currently, numerous studies focus on the absorption of heavy metals by EPS, but less attention has been paid to the effects of EPS on the plants. This study explored the effects of EPS from Lactobacillus plantarum LPC-1 on the structure and function of cell walls in rice seedling roots under cadmium (Cd) stress. The results showed that EPS could regulate the remodeling process of the cell walls of rice roots. EPS affects the synthesis efficiency and the content of the substances that made up the cell wall, and thus plays an essential role in limiting the uptake and transport of Cd in rice root. Furthermore, EPS could induce plant resistance to heavy metals by regulating the lignin biosynthesis pathway in rice roots. Finally, the cell wall remodeling induced by EPS likely contributes to plant stress responses by activating the reactive oxygen species (ROS) signaling.

Feeding Lactic Acid Bacteria with Different Sugars: Effect on Exopolysaccharides (EPS) Production and Their Molecular Characteristics

Exopolysaccharides (EPS) are complex molecules produced by some microorganisms and used in foods as texturizers and stabilizers, their properties depending on their chemical structure. In this work, three different lactic acid bacteria (LAB), were tested for their ability to produce EPS, by using five different mono- and disaccharides as their sole carbon source. The growth and acidifying ability were analysed, the EPSs were quantified by the official method AOAC 991.43, and their chemical structure was investigated. The amount of EPS varied from 0.71 g/L to 2.38 g/L, and maltose was the best sugar for EPS production by Lacticaseibacillus paracasei 2333. Lacticaseibacillus rhamnosus 1019 produced the highest amount when fed with lactose, whereas the EPS amount of Lactobacillus bulgaricus 1932 was not significantly different depending on the sugar type. The EPS chains consisted of fructose, galactose, glucose, mannose, ribose, glucosamine, galactosamine, and in some cases rhamnose in different proportions, depending on the strain and carbon source. The molecular weight of EPS ranged from <10 KDa to >500 KDa and was again highly dependent on the strain and the sugar used, suggesting the possibility of growing different strains under different conditions to obtain EPS with different potential applications in the food system.

Effect of Substrate Composition on Yield and Antioxidative Activity of Exopolysaccharides From Lactobacillus fermentum B62

Exopolysaccharides (EPS) can not only give food a unique texture but also has antioxidant capacities. To select the medium composition that influences the yield and antioxidative activity of EPS, Plackett–Burman (PB) design was employed to appraise the effects of carbon sources, nitrogen sources, and inorganic salts on yield and DPPH free radical scavenging (DPPH-FRS) rate of EPS in MRS medium fermented by Lactobacillus fermentum B62. The result indicated that sucrose (p<0.01), peptone (p<0.01), and KH2PO4 (p<0.001) had the most distinguishing comprehensive effects on yield and DPPH-FRS rate of EPS, and fructose also had a noticeable effect on the two factors (p<0.05, p<0.001, respectively). Additionally, glucose (p<0.05), soy protein (p<0.001), yeast extract (p<0.01), KH2PO4 (p<0.001) and Ca(H2PO4)2 (p<0.001) significantly positive affect the yield of EPS. And inulin (p<0.05), tryptone (p<0.001), beef extract powder(p<0.001), NaH2PO4 (p<0.01) and C2H3NaO2 (p<0.05) significantly positive affect the DPPH-FRS rate of EPS. Within the test ranges, sucrose, fructose, peptone and KH2PO4 all showed significant positive relativity to the yield and anti-oxidative activity of EPS.

Transcriptome analysis reveals the molecular mechanisms of the novel Lactobacillus pentosus pentocin against Bacillus cereus

The objective of this study was to investigate the antibacterial effect and mechanism of Lactobacillus pentosus pentocin against Bacillus cereus. The dynamic growth of B. cereus showed that the pentocin had strong antibacterial activity against the strain. The antibacterial mechanism focused on cytomembrane destruction, biofilms formation, DNA replication and protein synthesis of B. cereus. The scanning electron microscopy, transmission electron microscopy and flow cytometry analysis illustrated that the cytomembranes were destroyed, causing the leakage of internal cellular components. Transcriptome sequencing indicated that the genes (KinB, KinC and Spo0B) in two component systems signal pathway were down-regulated, which resulted in the inhibition of the spores and biofilms formation of B. cereus. The phosphorylation and autoinducer-2 import were inhibited by down-regulating the expression levels of LuxS and LsrB genes in quorum sensing signal pathway, which also suppressed biofilms formation of B. cereus. The K⁺ leakage activated the K⁺ transport channels by up-relating the genes (KdpA, KdpB and KdpC), promoting the entry of K⁺ from the extracellular. In addition, the pentocin interfered DNA replication and protein synthesis by regulating the genes associated with DNA replication (dnaX and holB), RNA degradation (cshA, rho, rnj, deaD, rny, dnaK, groEL and hfq) and ribosome function (rpsA, rpsO and rplS). In this article, we provide some novel insights into the molecular mechanism responsible for high antibacterial activity of the L. pentosus pentocin against B. cereus. And the pentocin might be a very promising natural preservative for controlling the B. cereus contaminations in foods.

Antioxidant and antimutagenic properties of probiotic Lactobacilli determined using LUX-biosensors

The initial screening of probiotic strains in vitro, carried out by different methods, may omit strains that are promising from the point of view of biotechnology or, conversely, mark as promising strains those that will lose activity when transferred in vivo. It is known that the release of metabolites by probiotic bacteria, in particular, lactobacilli, is highly dependent on the biochemical context. In this work, we modified the method that was previously successfully used for the selection of probiotics for poultry, based on their antioxidant and DNA-protective properties. A comparison was made of this activity on standard media and on an artificial intestinal medium that mimics the intestines of a bird. As a result, three Lactobacillus strains were selected, which not only exhibit antioxidant and DNA-protective properties but also do not lose these activities in an artificial intestinal medium.

Structural Characterisation and Assessment of the Novel Bacillus amyloliquefaciens RK3 Exopolysaccharide on the Improvement of Cognitive Function in Alzheimer's Disease Mice

In this study Bacillus amyloliquefaciens RK3 was isolated from a sugar mill effluent-contaminated soil and utilised to generate a potential polysaccharide with anti-Alzheimer's activity. Traditional and molecular methods were used to validate the strain. The polysaccharide produced by B. amyloliquefaciens RK3 was purified, and the yield was estimated to be 10.35 gL^-1. Following purification, the polysaccharide was structurally and chemically analysed. The structural analysis revealed the polysaccharide consists of α-d-mannopyranose (α-d-Manp) and β-d-galactopyranose (β-d-Galp) monosaccharide units connected through glycosidic linkages (i.e., β-d-Galp(1→6)β-d-Galp (1→6)β-d-Galp(1→2)β-d-Galp(1→2)[β-d-Galp(1→6)]β-d-Galp(1→2)α-d-Manp(1→6)α-d-Manp (1→6)α-d-Manp(1→6)α-d-Manp(1→6)α-d-Manp). The scanning electron microscopy and energy-dispersive X-ray spectroscopy imaging of polysaccharides emphasise their compactness and branching in the usual tubular heteropolysaccharide structure. The purified exopolysaccharide significantly impacted the plaques formed by the amyloid proteins during Alzheimer's disease. Further, the results also highlighted the potential applicability of exopolysaccharide in various industrial and pharmaceutical applications.

Genomic Analysis for Antioxidant Property of Lactobacillus plantarum FLPL05 from Chinese Longevity People

Antioxidant activity is one of the important probiotic characteristics for lactic acid bacteria including Lactobacillus plantarum, which is used for food fermentation or as a probiotic supplement. L. plantarum FLPL05 is a novel strain originally isolated from a healthy elderly individual of longevity. The organism has been demonstrated to exhibit high antioxidant property. However, there are limited genomic insights into the antioxidant properties of this organism. In this study, we performed whole-genome analysis regarding its antioxidant property. L. plantarum FLPL05 exhibited higher antioxidant activity compared with that of L. plantarum strains ATCC14917, ATCC8014, and WCFS1. The antioxidant capacity of L. plantarum FLPL05 was genetically linked to its antioxidant system, i.e., glutathione and thioredoxin involved in global regulation of defense against hydrogen peroxide challenge. L. plantarum FLPL05 was further examined for its antioxidant potential in D-Gal-induced aging mice and exhibited a significant increase in the activity of serum glutathione peroxidase (GSH-PX) and a decrease in the level of malondialdehyde (MDA). Moreover, our analyses exhibited a complete gene cluster including plnA, plnB, plnC, plnD, plnE, plnF, plnG, plnH, plnI, plnJ, plnK, plnM, plnN, plnO, plnP, plnQ, plnST, plnU, plnV, plnW, plnX, and plnY for production of bacteriocin. Our results suggest that L. plantarum FLPL05 could be a probiotic candidate.

Vaginal microbiota and the potential of Lactobacillus derivatives in maintaining vaginal health

Human vagina is colonised by a diverse array of microorganisms that make up the normal microbiota and mycobiota. Lactobacillus is the most frequently isolated microorganism from the healthy human vagina, this includes Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus iners, and Lactobacillus jensenii. These vaginal lactobacilli have been touted to prevent invasion of pathogens by keeping their population in check. However, the disruption of vaginal ecosystem contributes to the overgrowth of pathogens which causes complicated vaginal infections such as bacterial vaginosis (BV), sexually transmitted infections (STIs), and vulvovaginal candidiasis (VVC). Predisposing factors such as menses, pregnancy, sexual practice, uncontrolled usage of antibiotics, and vaginal douching can alter the microbial community. Therefore, the composition of vaginal microbiota serves an important role in determining vagina health. Owing to their Generally Recognised as Safe (GRAS) status, lactobacilli have been widely utilised as one of the alternatives besides conventional antimicrobial treatment against vaginal pathogens for the prevention of chronic vaginitis and the restoration of vaginal ecosystem. In addition, the effectiveness of Lactobacillus as prophylaxis has also been well-founded in long-term administration. This review aimed to highlight the beneficial effects of lactobacilli derivatives (i.e. surface-active molecules) with anti-biofilm, antioxidant, pathogen-inhibition, and immunomodulation activities in developing remedies for vaginal infections. We also discuss the current challenges in the implementation of the use of lactobacilli derivatives in promotion of human health. In the current review, we intend to provide insights for the development of lactobacilli derivatives as a complementary or alternative medicine to conventional probiotic therapy in vaginal health.

Exopolysaccharides from Lactobacillus kiferi as adjuvant enhanced the immuno-protective against Staphylococcus aureus infection

Exopolysaccharides from lactic acid bacteria (LAB) have gained more attention due to their health benefits. Most research on LAB EPS focuses on antitumor and antioxidant activities. To our knowledge, the immunoadjuvant activity of LAB EPS has not been thoroughly studied. In this study, the EPS produced by Lactobacillus kiferi WXD029 were purified by ethanol precipitation and column chromatography fractionation. The molecular weight of the EPS was 3.423 × 10⁵ Da and was mainly composed of Glu, GlcN, and GalN in a molar ratio of 3.1:1:1. In vitro, EPS could significantly enhance the proliferation and phagocytic activity as well as induce the production of NO, TNF-α, IL-1β, and IL-6 in RAW264.7 cells. In vivo, the EPS adjuvant could increase the titers of S.aureus antigen-specific antibodies and markedly enhanced T cell proliferation. Notably, EPS adjuvant also induced a strong potential Th1, Th2 and Th17-cell mixture responses. Furthermore, immunization with S.aureus antigen plus EPS adjuvant induced a protective effect when compared with S.aureus antigen alone in murine bacteremia, pneumonia and mastitis model. Collectively, these results suggest that EPS derived from probiotic Lactobacillus kiferi strain is promising as an efficient adjuvant candidate for the prevention of S. aureus infections.

The gut microbiota attenuates muscle wasting by regulating energy metabolism in chemotherapy-induced malnutrition rats

BACKGROUND

Malnutrition is a common clinical symptom in cancer patients after chemotherapy, which is characterized by muscle wasting and metabolic dysregulation. The regulation of muscle metabolism by gut microbiota has been studied recently. However, there is no direct convincing evidence proving that manipulating gut microbiota homeostasis could regulate muscle metabolic disorder caused by chemotherapy. Here, we investigate the potential role of gut microbiota in the regulation of the muscle metabolism in 5-fluorouracil (5-Fu)-induced malnutrition rat model.

METHODS

Male Sprague-Dawley rats were randomly divided into two groups (n = 8/group): control group and 5-Fu group. In the 5-Fu group, rats received 5-Fu (40 mg/kg/day) by intraperitoneal injection for 4 days, and all rats were raised for 8 days. Nutritional status, muscle function, muscle metabolites, and gut microbiota were assessed. Fecal microbiota transplantation (FMT) was applied to explore the potential regulation of gut microbiota on muscle metabolism.

RESULTS

5-Fu-treated rats exhibited loss of body weight and food intake compared to control group. 5-Fu decreased the levels of total protein and albumin in serum, and significantly increased the levels of IL-6 and TNF-α in muscle tissue. Rats that received 5-Fu displayed concurrent reduction of muscle function and fiber size. Moreover, 5-Fu group showed a distinct profile of gut microbiota compared to control group, including the relative lower abundance of Firmicutes and a higher abundance of Proteobacteria and Verrucomicrobia. Fourteen differential muscle metabolites were identified between two groups, which were mainly related to glycolysis, amino acid metabolism, and TCA cycle pathway. Furthermore, fecal transplantation from healthy rats improved nutritional status and muscle function in 5-Fu-treated rats. Notably, FMT inhibited the inflammatory response in muscle, and reversed the changes of several differential muscle metabolites and energy metabolism in 5-Fu-treated rats.

CONCLUSIONS

Our study demonstrated that gut microbiota played an important role in the regulation of muscle metabolism and promoting muscle energy production in 5-Fu-induced malnutrition rats, suggesting the potential attenuation of chemotherapy-induced muscle wasting by manipulating gut microbiota homeostasis.

Effects of tetracycline on the relationship between the microbial community and oxidative stress in earthworms based on canonical correlation analysis

In this study, Eisenia fetida was taken as the test organism and tetracycline was taken as the stress compound. The artificial soil test was conducted to study the utilization intensity of different carbon sources (the Biolog-microplate supplied) by microorganisms under different stress times and stress concentrations. The changes in the in vivo key enzymes activities of earthworms and oxidative stress indicators, such as malondialdehyde (MDA), were explored. The canonical correlation analysis method was the first used to establish a analysis-model to explore the relationship between the functional diversity of microbial community and the oxidative stress in earthworms in vivo under different stress times and concentrations. Research shows: 1) after tetracycline stress, in the earthworm, the CAT, POD, SOD, GPX were related to the microbes that use carbohydrate carbon sources; the GST and AChE were related to the microbes that use polymer carbon sources; the MDA was related to the microbes that use carbon sources: amino acid, carboxylic acid and phenolic acid. 2) Under low concentrations of tetracycline stress, there was no significant relationship between the functional diversity of the microbial communities and the effects of oxidative stress at this concentration. The high concentration of tetracycline can be utilized to screen probiotics that alleviate the effects of oxidative stress. 3) The utilization of carbon sources by microbial community in the earthworm after stress can be used as biomarker of ecotoxicology. It provides a basic theoretical for adding beneficial carbon sources to combat oxidative damage in vivo.

Characterizations of microbial diversity and machine oil degrading microbes in machine oil contaminated soil

Microbial diversity in machine oil contaminated soil was determined by high-throughput amplicon sequencing technology. The diversity of culturable microbes in the contaminated soil was further characterized using polymerase chain reaction method. Proteobacteria and Bacteroidetes were the most dominant phyla and occupied 52.73 and 16.77%, respectively, while the most abundant genera were Methylotenera (21.62%) and Flavobacterium (3.06%) in the soil. In the culturable microbes, the major phyla were Firmicutes (46.15%) and Proteobacteria (37.36%) and the most abundant genera were Bacillus (42.86%) and Aeromonas (34.07%). Four isolated microbes with high machine oil degradation efficiency were selected to evaluate their characteristics on the oil degradation. All of them reached their highest oil degradation rate after 7 days of incubation. Most of them significantly increased their oil degradation rate by additional carbon or organic nitrogen source in the incubation medium. The oil degradation rate by combination of the four microbes at the same inoculation level was also higher than the rate from each individual microbe. The protocol and findings of this study are very useful for developing micro-bioremediation method to eliminate machine oil contaminants from soil.

Plant Growth Promoting Rhizobacterial Mitigation of Drought Stress in Crop Plants: Implications for Sustainable Agriculture

Abiotic stresses arising from climate change negates crop growth and yield, leading to food insecurity. Drought causes oxidative stress on plants, arising from excessive production of reactive oxygen species (ROS) due to inadequate CO2, which disrupts the photosynthetic machinery of plants. The use of conventional methods for the development of drought-tolerant crops is time-consuming, and the full adoption of modern biotechnology for crop enhancement is still regarded with prudence. Plant growth-promoting rhizobacteria (PGPR) could be used as an inexpensive and environmentally friendly approach for enhancing crop growth under environmental stress. The various direct and indirect mechanisms used for plant growth enhancement by PGPR were discussed. Synthesis of 1-aminocyclopropane−1-carboxylate (ACC) deaminase enhances plant nutrient uptake by breaking down plant ACC, thereby preventing ethylene accumulation, and enable plants to tolerate water stress. The exopolysaccharides produced also improves the ability of the soil to withhold water. PGPR enhances osmolyte production, which is effective in reducing the detrimental effects of ROS. Multifaceted PGPRs are potential candidates for biofertilizer production to lessen the detrimental effects of drought stress on crops cultivated in arid regions. This review proffered ways of augmenting their efficacy as bio-inoculants under field conditions and highlighted future prospects for sustainable agricultural productivity.