Polysaccharide Degradation by the Intestinal Microbiota and Its Influence on Human Health and Disease

Polysaccharides From the Roots of Millettia Speciosa Champ Modulate Gut Health and Ameliorate Cyclophosphamide-Induced Intestinal Injury and Immunosuppression

Cyclophosphamide (CTX), a common anticancer drug, can cause a variety of side effects such as immunosuppression and intestinal mucosal injury. Polysaccharides are the major bioactive components of the roots of Millettia Speciosa Champ and have gained attention for their immunomodulatory activity. This study was designed to evaluate the immunomodulatory effect of Millettia Speciosa Champ polysaccharide (MSCP) on CTX-induced mice and the possible mechanism. The results showed that MSCP attenuated the CTX-induced decrease in body weight and immune organ indices in mice and promoted the secretion of immune-related cytokines (IL-2, IL-4, IL-10, TNF-α, and IgG). Meanwhile, MSCP restored intestinal morphology, increased the ratio of villus height/crypt depth (V/C), and improved the number of goblet cells and mucins expression. At the mRNA level, MSCP activated the TLRs/MyD88/NF-κB p65 pathway and enhanced the expression of genes related to intestinal mucosal integrity (Occludin1, Claudin1, and MUC-2). In addition, MSCP as a prebiotic improved microbial community diversity, regulated the relative abundance of dominant microbiota from the phylum level to the genus level, restored CTX-induced gut microbial dysbiosis, and promoted short-chain fatty acid production in mice. Based on the present findings, MSCP may modulate the immune response depending on enhancing intestinal health, suggesting that MSCP holds promise as a promising immunostimulant in functional foods and drugs.

Dietary fibre complexity and its influence on functional groups of the human gut microbiota

The aim of this review is to provide an overview of the complex interactions between dietary fibre and the resident microbial community in the human gut. The microbiota influences both health maintenance and disease development. In the large intestine, the microbiota plays a crucial role in the degradation of dietary carbohydrates that remain undigested in the upper gut (non-digestible carbohydrates or fibre). Dietary fibre contains a variety of different types of carbohydrates, and its breakdown is facilitated by many different microbial enzymes. Some microbes, termed generalists, are able to degrade a range of different carbohydrates, whereas others are more specialised. Furthermore, the physicochemical characteristics of dietary fibre, such as whether it enters the gut in soluble or insoluble form, also likely influence which microbes can degrade it. A complex nutritional network therefore exists comprising primary degraders able to attack complex fibre and cross feeders that benefit from fibre breakdown intermediates or fermentation products. This leads predominately to the generation of the short-chain fatty acids (SCFA) acetate, propionate and butyrate, which exert various effects on host physiology, including the supply of energy, influencing glucose and lipid metabolism and anti-carcinogenic and anti-inflammatory actions. In order to effectively modulate the gut microbiota through diet, there is a need to better understand the complex competitive and cooperative interactions between gut microbes in dietary fibre breakdown, as well as how gut environmental factors and the physicochemical state of fibre originating from different types of diets influence microbial metabolism and ecology in the gut.

Dietary Energy Level Impacts the Performance of Donkeys by Manipulating the Gut Microbiome and Metabolome

Considerable evidence suggests that dietary energy levels and gut microbiota are pivotal for animal health and productivity. However, little information exists about the correlations among dietary energy level, performance, and the gut microbiota and metabolome of donkeys. The objective of this study was to investigate the mechanisms by which dietary energy content dictates the growth performance by modulating the intestinal microbiome and metabolome of donkeys. Thirty-six nine-month-old male Dezhou donkeys with similar body weights were randomly assigned to two groups fed low- or high-energy diets (LE or HE). The results showed that donkeys fed HE had increased (p < 0.05) the average daily gain (ADG) and feed efficiency (G/F) compared with those that received LE diet. The gut microbiota in both groups was dominated by the phyla Firmicutes and Bacteroidetes regardless of the dietary energy level. However, feeding HE to donkeys significantly decreased (p < 0.05) the ratio of Firmicutes to Bacteroidetes (F/B). Compared to the LE group, feeding HE specifically increased the abundances of unidentified_Prevotellaceae (p = 0.02) while decreasing the richness of unidentified_Ruminococcaceae (p = 0.05). Compared to the LE group, feeding the HE diet significantly (p < 0.05) upregulated certain metabolic pathways involving the aspartate metabolism and the urea cycle. In addition, the increased bacteria and metabolites in the HE-fed group exhibited a positive correlation with improved growth performance of donkeys. Taken together, feeding the HE diet increased the richness of Prevotellaceae and upregulated growth-related metabolic pathways, which may have contributed to the ameliorated growth performance of donkeys. Thus, it is a recommendable dietary strategy to feed HE diets to fattening donkeys for superior product performance and feed efficiency.

Supplementation of Alhagi honey polysaccharides contributes to the improvement of the intestinal immunity regulating the structure of intestinal flora in mice

Alhagi honey polysaccharides (AH), a main active component of Alhagi honey, are known to possess excellent pharmacological activities and have been widely used as dietary supplements in traditional Chinese medicine for thousands of years. This study is aimed to investigate the heath effect of AH on murine intestinal mucosal immune function and composition of the gut microbiome. ICR mice received daily intragastric administration of AH (three dosages, 200 mg kg^-1, 400 mg kg^-1, and 800 mg kg^-1) or saline for 7 consecutive days. Results indicated an improvement in the intestinal barrier function through increases in secretory immunoglobulin A (sIgA) and β-defensins. Simultaneously, AH also significantly stimulated IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ, and TNF-α cytokine secretion as compared to the control samples. Moreover, hematoxylin and eosin staining showed that AH enhanced the number of intraepithelial lymphocytes (IELs) in the small intestine. An obvious increase in the ratio of IgA⁺ cells of AH-treatment samples in the lamina propria was also detected by immunohistochemical staining. In addition, the CD3⁺, CD4⁺ and CD8⁺ T-cell ratio in mesenteric lymph nodes and Peyer's patches in the AH-treatment was significantly higher than that in the control group. Furthermore, 16S rDNA gene sequencing was used to monitor the dynamic changes in the gut microbiota. The result revealed that AH significantly increased the indexes of Shannon and obviously decreased the indexes of Simpson, suggesting the enhancement of the diversity and richness of the intestinal microbiome. Moreover, AH modulated the gut microbiome via increasing the abundance of probiotics and decreasing the levels of pathogenic bacteria. In summary, these results indicated that AH could be used as a prebiotic to enhance murine intestinal mucosal immunity and to modulate the gut microbiome.

Analysis of six tonB gene homologs in Bacteroides fragilis revealed that tonB3 is essential for survival in experimental intestinal colonization and intra-abdominal infection

The opportunistic, anaerobic pathogen and commensal of the human large intestinal tract, Bacteroides fragilis strain 638R, contains six predicted TonB proteins, termed TonB1-6, four ExbBs orthologs, ExbB1-4, and five ExbDs orthologs, ExbD1-5. The inner membrane TonB/ExbB/ExbD complex harvests energy from the proton motive force (Δp) and the TonB C-terminal domain interacts with and transduces energy to outer membrane TonB-dependent transporters (TBDTs). However, TonB's role in activating nearly one hundred TBDTs for nutrient acquisition in B. fragilis during intestinal colonization and extraintestinal infection has not been established. In this study, we show that growth was abolished in the ΔtonB3 mutant when heme, vitamin B12, Fe(III)-ferrichrome, starch, mucin-glycans, or N-linked glycans were used as a substrate for growth in vitro. Genetic complementation of the ΔtonB3 mutant with the tonB3 gene restored growth on these substrates. The ΔtonB1, ΔtonB2, ΔtonB4, ΔtonB5, and ΔtonB6 single mutants did not show a growth defect. This indicates that there was no functional compensation for the lack of TonB3, and it demonstrates that TonB3, alone, drives the TBDTs involved in the transport of essential nutrients. The ΔtonB3 mutant had a severe growth defect in a mouse model of intestinal colonization compared to the parent strain. This intestinal growth defect was enhanced in the ΔtonB3 ΔtonB6 double mutant strain which completely lost its ability to colonize the mouse intestinal tract compared to the parent strain. The ΔtonB1, ΔtonB2, ΔtonB4, and ΔtonB5 mutants did not significantly affect intestinal colonization. Moreover, the survival of the ΔtonB3 mutant strain was completely eradicated in a rat model of intra-abdominal infection. Taken together, these findings show that TonB3 was essential for survival in vivo. The genetic organization of tonB1, tonB2, tonB4, tonB5, and tonB6 gene orthologs indicates that they may interact with periplasmic and nonreceptor outer membrane proteins, but the physiological relevance of this has not been defined. Because anaerobic fermentation metabolism yields a lower Δp than aerobic respiration and B. fragilis has a reduced redox state in its periplasmic space - in contrast to an oxidative environment in aerobes - it remains to be determined if the diverse system of TonB/ExbB/ExbD orthologs encoded by B. fragilis have an increased sensitivity to PMF (relative to aerobic bacteria) to allow for the harvesting of energy under anaerobic conditions.

In vitro digestibility and prebiotic activities of a bioactive polysaccharide from Moringa oleifera leaves

In this study, the digestion and fermentation properties of a bioactive polysaccharide (MOP-2) purified from Moringa oleifera leaves and its impact on the human colonic microbiota were determined using simulated saliva-gastrointestinal digestion and human fecal fermentation models in vitro. The results showed that the simulated saliva and gastric juices had no effect on the average molecular weight (MW) of MOP-2. The MW of MOP-2 slightly decreased from 155.29 to 145.02 kDa during intestinal digestion, and the reducing sugar content increased from 0.159 to 0.234 mg/ml, indicating that MOP-2 was partially degraded during intestinal digestion. During fermentation, MOP-2 was largely used by human fecal inoculums. Notably, MOP-2 could significantly regulate the structure of the microbial community by improving the relative abundances of some beneficial gut microbiota, such as Phascolarctobacterium, Coprococcus, Roseburia, and Bacteroides. Additionally, after fermentation for 48 hr, MOP-2 could significantly improve the production of short-chain fatty acids, especially n-butyric acid, acetic acid, propionic acid, and n-valeric acid. These results suggested that MOP-2 could potentially be a gut microbiota manipulator aimed at promoting gut health. PRACTICAL APPLICATIONS: Gut microbial community is an important part of the human intestinal environment. The health of gut microbiota is closely associated with host heath. This work reported that a polysaccharide (MOP-2) purified from Moringa oleifera leaves could modulate the microbial structure by improving the relative abundances of some beneficial gut microbiota, which provided useful information for the application of MOP-2 as a prebiotic additive in food industry.

Influence of the Microbiome on Chronic Rhinosinusitis With and Without Polyps: An Evolving Discussion

Chronic rhinosinusitis (CRS) is widely prevalent within the population and often leads to decreased quality of life, among other related health complications. CRS has classically been stratified by the presence of nasal polyps (CRSwNP) or the absence nasal polyps (CRSsNP). Management of these conditions remains a challenge as investigators continue to uncover potential etiologies and therapeutic targets. Recently, attention has been given to the sinunasal microbiota as both an inciting and protective influence of CRS development. The healthy sinunasal microbiologic environment is largely composed of bacteria, with the most frequent strains including Staphylococcus aureus, Streptococcus epidermidis, and Corynebacterium genera. Disruptions in this milieu, particularly increases in S. aureus concentration, have been hypothesized to perpetuate both Th1 and Th2 inflammatory changes within the nasal mucosa, leading to CRS exacerbation and potential polyp formation. Other contributors to the sinunasal microbiota include fungi, viruses, and bacteriophages which may directly contribute to underlying inflammation or impact bacterial prevalence. Modifiable risk factors, such as smoking, have also been linked to microbiota alterations. Research interest in CRS continues to expand, and thus the goal of this review is to provide clinicians and investigators alike with a current discussion on the microbiologic influence on CRS development, particularly with respect to the expression of various phenotypes. Although this subject is rapidly evolving, a greater understanding of these potential factors may lead to novel research and targeted therapies for this often difficult to treat condition.

Align resistant starch structures from plant-based foods with human gut microbiome for personalized health promotion

Resistant starch (RS) is beneficial for human health through its interactions with gut microbiota. However, the alignment between RS structures with gut microbiota profile and consequentially health benefits remain elusive. This review summarizes current understanding of RS complex structures and their interactions with the gut microbiota, aiming to highlight the possibility of manipulating RS structures for a targeted and predictable gut microbiota shift for human health in a personalized way. Current definition of RS types is strongly associated with starch digestion behaviors in small intestine, which does not precisely reflect their interactions with human gut microbiota. Distinct alterations of gut microbiota could be associated with the same RS type. The principles to describe the specificity of different RS structural characteristics in terms of aligning with human gut microbiota shift was proposed in this review, which could result in new definitions of RS types from the microbial perspectives. To consider the highly variable personal features, a machine-learning algorithm to integrate different personalized factors and better understand the complex interaction between RS and gut microbiota and its effects on individual health was explained. This review contains important information to bring interactions between RS and gut microbiota to translational practice.

Gut microbiota response to sulfated sea cucumber polysaccharides in a differential manner using an in vitro fermentation model

Sea cucumber Stichopus japonicus has been consumed as high-valued seafood in Asian, and its sulfated polysaccharide (SCSPsj) has been inferred to benefit the host health via modulating gut microbiota composition. The present study compared the responses of gut microbiota communities from different donors to SCSPsj, and the key bacteria were identified by 16S rRNA gene sequencing analysis and in vitro fermentation with specific bacteria. Gut microbiota communities from 6 donors (A ~ F) utilized the polysaccharides to different degrees in vitro fermentation. Further comparison of Samples A and C demonstrated that Sample C with the relatively strong SCSPsj utilization capability possessed more Parabacteroides while Sample A contained more Bacteroides. Further in vitro fermentation of SCSPsj with 10 Parabacteroides and Bacteroides species suggests that Parabacteroides distasonis, enriched in Sample C, plays a critical role in the utilization of the polysaccharides. Moreover, short chain fatty acids and the metabolite profiles of Samples A and C were also compared, and the results showed that more beneficial metabolites were accumulated by the microbiota community consuming more sulfated sea cucumber polysaccharides. Our findings revealed that certain key members of gut microbiota, such as Parabacteroides distasonis, are critical for SCSPsj utilization in gut so as to influence the benefits of the polysaccharide supplement for host. Thus, to obtain better functional outcome for sulfated sea cucumber polysaccharides and sea cucumber, more attention needs to be paid to the effects of inter-individual differences in microbiota community structure.

In vitro Colon Fermentation of Soluble Arabinoxylan Is Modified Through Milling and Extrusion

Dietary fibers such as arabinoxylan (AX) are promising food constituents to prevent particular diet-related chronic diseases because of their prebiotic properties. Arabinoxylan fermentation by the gut microbiota depends on the structural architecture of AX, which can be modified during food processing and consequently affect its prebiotic potential, but it is little investigated. Therefore, the aim of this study was to evaluate the effects of naturally occurring and processing-induced structural alterations of the soluble AX of wheat bran and rye flour on the in vitro human colon fermentation. It was found that fermentation behavior is strongly linked to the AX fine structure and their processing-induced modifications. The short-chain fatty acid (SCFA) metabolism, acidification kinetics, bacterial growth, and bacterial composition revealed that wheat bran AX (WBAX) was fermented faster than rye flour AX. Increased levels of bound phenolic acids resulting from processing were identified as the inhibiting factor for AX fermentation kinetics. Bacterial genera promoted by AX varied between AX source and processing type, but also between microbiota. Extruded WBAX promoted butyrate production and growth of butyrate-producing Faecalibacterium in the butyrogenic microbiota while it did not enhance fermentation and inhibited the growth of Prevotella in the propiogenic microbiota. We anticipate that the findings of this study are a starting point for further investigation on the impact of processing-induced changes on the prebiotic potential of dietary fibers prior to human studies.

Tripartite relationship between gut microbiota, intestinal mucus and dietary fibers: towards preventive strategies against enteric infections

The human gut is inhabited by a large variety of microorganims involved in many physiological processes and collectively referred as to gut microbiota. Disrupted microbiome has been associated with negative health outcomes and especially could promote the onset of enteric infections. To sustain their growth and persistence within the human digestive tract, gut microbes and enteric pathogens rely on two main polysaccharide compartments, namely dietary fibers and mucus carbohydrates. Several evidences suggest that the three-way relationship between gut microbiota, dietary fibers and mucus layer could unravel the capacity of enteric pathogens to colonise the human digestive tract and ultimately lead to infection. The review starts by shedding light on similarities and differences between dietary fibers and mucus carbohydrates structures and functions. Next, we provide an overview of the interactions of these two components with the third partner, namely, the gut microbiota, under health and disease situations. The review will then provide insights into the relevance of using dietary fibers interventions to prevent enteric infections with a focus on gut microbial imbalance and impaired-mucus integrity. Facing the numerous challenges in studying microbiota-pathogen-dietary fiber-mucus interactions, we lastly describe the characteristics and potentialities of currently available in vitro models of the human gut.

Architecturally complex O-glycopeptidases are customized for mucin recognition and hydrolysis

A challenge faced by peptidases is the recognition of highly diverse substrates. A feature of some peptidase families is the capacity to specifically use post-translationally added glycans present on their protein substrates as a recognition determinant. This is ultimately critical to enabling peptide bond hydrolysis. This class of enzyme is also frequently large and architecturally sophisticated. However, the molecular details underpinning glycan recognition by these O-glycopeptidases, the importance of these interactions, and the functional roles of their ancillary domains remain unclear. Here, using the Clostridium perfringens ZmpA, ZmpB, and ZmpC M60 peptidases as model proteins, we provide structural and functional insight into how these intricate proteins recognize glycans as part of catalytic and noncatalytic substrate recognition. Structural, kinetic, and mutagenic analyses support the key role of glycan recognition within the M60 domain catalytic site, though they point to ZmpA as an apparently inactive enzyme. Wider examination of the Zmp domain content reveals noncatalytic carbohydrate binding as a feature of these proteins. The complete three-dimensional structure of ZmpB provides rare insight into the overall molecular organization of a highly multimodular enzyme and reveals how the interplay of individual domain function may influence biological activity. O-glycopeptidases frequently occur in host-adapted microbes that inhabit or attack mucus layers. Therefore, we anticipate that these results will be fundamental to informing more detailed models of how the glycoproteins that are abundant in mucus are destroyed as part of pathogenic processes or liberated as energy sources during normal commensal lifestyles.

Beneficial Effects of Holothuria leucospilota Polysaccharides on Fermentability In Vivo and In Vitro

This work aimed to investigate the in-vitro and in-vivo fermentation behaviors of Holothuria leucospilota Polysaccharides (HLP) and the impact on mouse liver antioxidant activity. HLP showed excellent fermentability during in vitro experiments, which was characterized by increased levels of total sugar consumption and short-chain fatty acids (SCFAs). During in vitro fecal fermentation, the fucose contents in the HLP fermentation products (0.174 mg/mL) were higher than those of xylose and galactosamine during the first three hours, and fucose disappeared after 24 h. The concentrations of the generated SCFAs increased to 111.13 mmol/mL after in-vitro fermentation at 48 h. After 28 days of oral administration, the SCFA contents that were detected in the feces of mice treated with high HLP doses were significantly higher than those in the feces of mice treated with lower doses and the normal group. In addition, histological observations demonstrated that HLP increased the number of goblet cells without causing hepatocellular injury. Moreover, the increased glutathione peroxidase (GSH-Px) and superoxidase dismutase (SOD) activities and decreased malondialdehyde (MDA) contents in the mouse livers treated with HLP suggested the good performance of HLP with respect to liver antioxidants.

Simulated digestion and fecal fermentation behaviors of exopolysaccharides from Paecilomyces cicadae TJJ1213 and its effects on human gut microbiota

This study aimed to explore the in vitro simulated digestion and fecal fermentation behaviors of two purified exopolysaccharide fractions (EPS1 and EPS2) from Paecilomyces cicadae TJJ1213 and its effects on human gut microbiota composition. Results showed that EPS1 and EPS2 could not be digested by saliva-gastrointestinal. After fecal fermentation, however, the molecular weight of EPS1 and EPS2 significantly decreased, and the molar ratios of the monosaccharide composition remarkably changed, indicating that EPS1 and EPS2 could be degraded and consumed by human gut microbiota. Notably, EPS1 and EPS2 could significantly modulate the composition, via increasing the relative abundances of Bacteroides and Phascolarctobacterium and decreasing the pathogenic bacteria Escherichia-Shigella, Klebsiella and Fusobacterium. In addition, EPS1 and EPS2 also could promote the production of short-chain fatty acids during fermentation for 24 h. These results suggest that EPS from Paecilomyces cicadae TJJ1213 can be used as a functional food to improve health and prevent diseases by promoting gut health.

Exploring the impact of gut microbiota and diet on breast cancer risk and progression

There is emerging evidence that resident microbiota communities, that is, the microbiota, play a key role in cancer outcomes and anticancer responses. Although this has been relatively well studied in colorectal cancer and melanoma, other cancers, such as breast cancer (BrCa), have been largely overlooked to date. Importantly, many of the environmental factors associated with BrCa incidence and progression are also known to impact the microbiota, for example, diet and antibiotics. Here, we explore BrCa risk factors from large epidemiology studies and microbiota associations, and more recent studies that have directly profiled BrCa patients' gut microbiotas. We also discuss how in vivo studies have begun to unravel the immune mechanisms whereby the microbiota may influence BrCa responses, and finally we examine how diet and specific nutrients are also linked to BrCa outcomes. We also consider future research avenues and important considerations with respect to study design and implementation, and we highlight some of the important unresolved questions, which currently limit our overall understanding of the mechanisms underpinning microbiota-BrCa responses.

Arc1 and the microbiota together modulate growth and metabolic traits in Drosophila

Perturbations to animal-associated microbial communities (the microbiota) have deleterious effects on various aspects of host fitness, but the molecular processes underlying these impacts are poorly understood. Here, we identify a connection between the microbiota and the neuronal factor Arc1 that affects growth and metabolism in Drosophila. We find that Arc1 exhibits tissue-specific microbiota-dependent expression changes, and that germ-free flies bearing a null mutation of Arc1 exhibit delayed and stunted larval growth, along with a variety of molecular, cellular and organismal traits indicative of metabolic dysregulation. Remarkably, we show that the majority of these phenotypes can be fully suppressed by mono-association with a single Acetobacter sp. isolate, through mechanisms involving both bacterial diet modification and live bacteria. Additionally, we provide evidence that Arc1 function in key neuroendocrine cells of the larval brain modulates growth and metabolic homeostasis under germ-free conditions. Our results reveal a role for Arc1 in modulating physiological responses to the microbial environment, and highlight how host-microbe interactions can profoundly impact the phenotypic consequences of genetic mutations in an animal host.

Polysaccharide Structures and Their Hypocholesterolemic Potential

Several classes of polysaccharides have been described to have hypocholesterolemic potential, namely cholesterol bioaccessibility and bioavailability. This review will highlight the main mechanisms by which polysaccharides are known to affect cholesterol homeostasis at the intestine, namely the effect (i) of polysaccharide viscosity and its influence on cholesterol bioaccessibility; (ii) on bile salt sequestration and its dependence on the structural diversity of polysaccharides; (iii) of bio-transformations of polysaccharides and bile salts by the gut microbiota. Different quantitative structure–hypocholesterolemic activity relationships have been explored depending on the mechanism involved, and these were based on polysaccharide physicochemical properties, such as sugar composition and ramification degree, linkage type, size/molecular weight, and charge. The information gathered will support the rationalization of polysaccharides’ effect on cholesterol homeostasis and highlight predictive rules towards the development of customized hypocholesterolemic functional food.

Prebiotic inulin as a treatment of obesity related nonalcoholic fatty liver disease through gut microbiota: a critical review

The microbial-derived products, including short chain fatty acids, lipopolysaccharide and secondary bile acids, have been shown to participate in the regulation of hepatic lipid metabolism. Previous studies have demonstrated that prebiotics, such as oligosaccharide and inulin, have abilities to change the concentration of microbial-derived products through modulating the microbial community structure, thus controlling body weight and alleviating hepatic fat accumulation. However, recent evidence indicates that there are individual differences in host response upon inulin treatment due to the differences in host microbial composition before dietary intervention. Probably it is because of the multiple relationships among bacterial species (e.g., competition and mutualism), which play key roles in the degradation of inulin and the regulation of microbial structure. Thereby, analyzing the composition and function of initial gut microbiota is essential for improving the efficacy of prebiotics supplementation. Furthermore, considering that different structures of polysaccharides can be used by different microorganisms, the chemical structure of processed inulin should be tested before using prebiotic inulin to treat obesity related nonalcoholic fatty liver disease.

Impact of Phlorotannin Extracts from Fucus vesiculosus on Human Gut Microbiota

Recent studies indicate that plant polyphenols could be pointed as potential prebiotic candidates since they may interact with the gut microbiota, stimulating its growth and the production of metabolites. However, little is known about the fate of brown seaweeds' phlorotannins during their passage throughout the gastrointestinal tract. This work aimed to evaluate the stability and bioaccessibility of Fucus vesiculosus phlorotannins after being submitted to a simulated digestive process, as well as their possible modulatory effects on gut microbiota and short-chain fatty acids production following a fermentation procedure using fecal inoculates to mimic the conditions of the large intestine. The stability of phlorotannins throughout the gastrointestinal tract was reduced, with a bioaccessibility index between 2 and 14%. Moreover, slight alterations in the growth of certain commensal bacteria were noticed, with Enterococcus spp. being the most enhanced group. Likewise, F. vesiculosus phlorotannins displayed striking capacity to enhance the levels of propionate and butyrate, which are two important short-chain fatty acids known for their role in intestinal homeostasis. In summary, this work provides valuable information regarding the behavior of F. vesiculosus phlorotannins along the gastrointestinal tract, presenting clear evidence that these compounds can positively contribute to the maintenance of a healthy gastrointestinal condition.

Fermentation Profile and Probiotic-Related Characteristics of Bifidobacterium longum MC-42

This article presents new data on Bifidobacterium longum MC-42—a strain that has been actively used for the preparation of commercial dairy products in Russia for almost 40 years. It was demonstrated that this strain possesses high activities of β-galactosidase, α-glucosidase, and leucine arylaminidase; inhibits the growth of pathogens such as Salmonella typhimurium, Staphylococcus aureus, and Escherichia coli; and can efficiently remove cholesterol from the cultural medium. The resistance of B. longum MC-42 determined for 15 commonly used antibiotics was in agreement with those previously reported for Bifidobacterium spp. The absence of frequently transmittable antibiotic resistance genes in the genome and the lack of undesirable activity of β-glucuronidase proved the safe use of B. longum МС-42 as a probiotic and starter culture. Additionally, the impact of two growth-promoting additives—yeast extract or milk protein hydrolysate containing supplementation—on the B. longum MC-42 fermentation profile was assessed. The introduction of these additives increases the maximum attainable viable cell count by orders of magnitude, significantly changed the profile of aminopeptidase activities in extracellular extracts, and influenced the antioxidant and antihypertensive properties of the obtained fermented products.

A polysaccharide from natural Cordyceps sinensis regulates the intestinal immunity and gut microbiota in mice with cyclophosphamide-induced intestinal injury

A polysaccharide from Cordyceps sinensis (NCSP) was reported to attenuate intestinal injury and regulate the balance of T helper (Th)1/Th2 cells in immunosuppressed mice. However, whether it influences Th17 and regulatory T (Treg) cells as well as gut ecology remains unknown. In the present study, the intestinal injury mouse model was also established by intraperitoneal injection of cyclophosphamide (Cy) for three consecutive days. NCSP was found to increase the number of CD4⁺ T cells, stimulate the secretion of interleukins (IL)-17 and IL-21, and the expression of transcription factor (retinoic acid-related orphan receptor (ROR)-γt). The levels of transforming growth factor (TGF)-β3 and transcription factor (forkhead box (Fox)p-3) were increased in NCSP-treated groups. Moreover, NCSP upregulated the mRNA expression of toll like receptors (TLR-2, -6 and -9), while it downregulated the TLR-4 expression. In addition, NCSP modulated the intestinal microbiota composition and increased the levels of SCFAs. These findings indicated that NCSP may enhance intestinal immunity and have the potential to become a prebiotic to regulate intestinal microbiota.

Reshaping of bacterial molecular hydrogen metabolism contributes to the outgrowth of commensal E. coli during gut inflammation

The composition of gut-associated microbial communities changes during intestinal inflammation, including an expansion of Enterobacteriaceae populations. The mechanisms underlying microbiota changes during inflammation are incompletely understood. Here, we analyzed previously published metagenomic datasets with a focus on microbial hydrogen metabolism. The bacterial genomes in the inflamed murine gut and in patients with inflammatory bowel disease contained more genes encoding predicted hydrogen-utilizing hydrogenases compared to communities found under non-inflamed conditions. To validate these findings, we investigated hydrogen metabolism of Escherichia coli, a representative Enterobacteriaceae, in mouse models of colitis. E. coli mutants lacking hydrogenase-1 and hydrogenase-2 displayed decreased fitness during colonization of the inflamed cecum and colon. Utilization of molecular hydrogen was in part dependent on respiration of inflammation-derived electron acceptors. This work highlights the contribution of hydrogenases to alterations of the gut microbiota in the context of non-infectious colitis.

Human Gut Faecalibacterium prausnitzii Deploys a Highly Efficient Conserved System To Cross-Feed on β-Mannan-Derived Oligosaccharides

β-Mannans are hemicelluloses that are abundant in modern diets as components in seed endosperms and common additives in processed food. Currently, the collective understanding of β-mannan saccharification in the human colon is limited to a few keystone species, which presumably liberate low-molecular-weight mannooligosaccharide fragments that become directly available to the surrounding microbial community. Here, we show that a dominant butyrate producer in the human gut, Faecalibacterium prausnitzii, is able to acquire and degrade various β-mannooligosaccharides (β-MOS), which are derived by the primary mannanolytic activity of neighboring gut microbiota. Detailed biochemical analyses of selected protein components from their two β-MOS utilization loci (F. prausnitzii β-MOS utilization loci [FpMULs]) supported a concerted model whereby the imported β-MOS are stepwise disassembled intracellularly by highly adapted enzymes. Coculturing experiments of F. prausnitzii with the primary degraders Bacteroides ovatus and Roseburia intestinalis on polymeric β-mannan resulted in syntrophic growth, thus confirming the high efficiency of the FpMULs' uptake system. Genomic comparison with human F. prausnitzii strains and analyses of 2,441 public human metagenomes revealed that FpMULs are highly conserved and distributed worldwide. Together, our results provide a significant advance in the knowledge of β-mannan metabolism and the degree to which its degradation is mediated by cross-feeding interactions between prominent beneficial microbes in the human gut. IMPORTANCE Commensal butyrate-producing bacteria belonging to the Firmicutes phylum are abundant in the human gut and are crucial for maintaining health. Currently, insight is lacking into how they target otherwise indigestible dietary fibers and into the trophic interactions they establish with other glycan degraders in the competitive gut environment. By combining cultivation, genomic, and detailed biochemical analyses, this work reveals the mechanism enabling F. prausnitzii, as a model Ruminococcaceae within Firmicutes, to cross-feed and access β-mannan-derived oligosaccharides released in the gut ecosystem by the action of primary degraders. A comprehensive survey of human gut metagenomes shows that FpMULs are ubiquitous in human populations globally, highlighting the importance of microbial metabolism of β-mannans/β-MOS as a common dietary component. Our findings provide a mechanistic understanding of the β-MOS utilization capability by F. prausnitzii that may be exploited to select dietary formulations specifically boosting this beneficial symbiont, and thus butyrate production, in the gut.

Molecular-structure evolution during in vitro fermentation of granular high-amylose wheat starch is different to in vitro digestion

This study investigates the evolution of the distributions of whole molecular size and of chain length of granular wheat starches (37 ~ 93% amylose content), subjected to in vitro fermentation with a porcine faecal inoculum or digestion with pancreatic enzymes. The results showed that the molecular structures of high-amylose starch (HAS) unfermented residues largely remained unchanged during the fermentation process, while wild-type starch (37% amylose content) showed a preferential degradation of the amylopectin fraction. In contrast, under simulated digestion conditions, the undigested residues of HAS showed structural changes, including a decrease in amylose content, a shift of amylose peak position towards lower degrees of polymerisation, and an enzyme-resistant fraction. These changes of starch structure are likely to be dependent on the different starch-degrading enzyme activities present in pancreatic vs. microbial systems. Molecular changes in response to fermentation metabolism revealed by size-exclusion chromatography can help understand the microbial utilization of resistant starch.

Similar hypoglycemic effects of glucomannan and its enzyme degraded products from Amorphophallus albus on type 2 diabetes mellitus in mice and potential mechanisms

In the present study, the hypoglycemic effects of glucomannan (AGM) and its enzyme-degraded products from Amorphophallus albus were investigated. Four degraded products were prepared through ultrafiltration of β-glucanase-degraded products of AGM. The hypoglycemic activities were evaluated in HFD-STZ-induced type 2 diabetes mellitus (T2DM) mice, and the diversity of gut bacteria was analyzed by 16S rRNA gene sequencing; the fecal short chain fatty acids (SCFAs) and endogenous metabolites were determined by UPLC-QTOF-MS/MS. It was found that AGM and its enzyme-degraded products, though with different molecular weights, had similar β-glycosidic bonds and monosaccharide compositions, exerted similar strength of hypoglycemic effects, and reinstated with a similar extent the disordered gut microbiota and the contents of SCFAs and endogenous metabolites. It was speculated that the hypoglycemic activity of AGM is decided by not the molecular weight but the glycosidic bonds/monosaccharide composition of AGM, which might be structurally specific to the gut bacteria, and thus certain SCFAs and endogenous metabolites that are related to the occurrence and therapy of T2DM. This study provides a scientific basis for using AGM as potential prebiotics beneficial for prevention or therapeutic treatment of T2DM.

A Nitrogen Metabolic Enzyme Provides Salmonella Fitness Advantage by Promoting Utilization of Microbiota-Derived Carbon Source

Microbes support their growth in vertebrate hosts by exploiting a large variety of dietary components as nutrients, which determines the composition of gut microbiota. A pathogen Salmonella expands by utilizing 1,2-propanediol, a microbiota-fermented product, during mucosal inflammation. However, it remains largely unknown how the pathogen decides which nutrient to consume from the complex mixture in the gut. Here, we show that Salmonella enterica serovar Typhimurium utilizes 1,2-propanediol by EIIANtr (a nitrogen-metabolic PTS component implicated in virulence)-mediated regulation of the pdu operon, thereby expanding in the murine intestine. Propionyl-CoA, a metabolic intermediate produced by 1,2-propanediol catabolism, elevates EIIANtr protein amounts, entailing positive feedback, thereby boosting the 1,2-propanediol-utilization process. EIIANtr promotes pdu expression by enhancing glutathione synthesis. CRP (cAMP receptor protein) induces pdu genes by increasing EIIANtr expression in response to glucose availability. Notably, EIIANtr-mediated 1,2-propanediol-utilization conferred a growth benefit even under high glucose conditions which reduces CRP activity. The EIIANtr-mediated activation is likely conserved in pathogenic enterobacteria including Escherichia coli. Collectively, our findings suggest that Salmonella promotes its fitness by precisely modulating the utilization system for microbiota-derived carbon source. They also suggest that Salmonella may integrate signals, processed via EIIANtr, into its metabolic program as well as virulence circuit.

Classification, structural biology, and applications of mucin domain-targeting proteases

Epithelial surfaces throughout the body are coated by mucins, a class of proteins carrying domains characterized by a high density of O-glycosylated serine and threonine residues. The resulting mucosal layers form crucial host-microbe interfaces that prevent the translocation of microbes while also selecting for distinct bacteria via the presented glycan repertoire. The intricate interplay between mucus production and breakdown thus determines the composition of the microbiota maintained within these mucosal environments, which can have a large influence on the host during both homeostasis and disease. Most research to date on mucus breakdown has focused on glycosidases that trim glycan structures to release monosaccharides as a source of nutrients. More recent work has uncovered the existence of mucin-type O-glycosylation-dependent proteases that are secreted by pathogens, commensals, and mutualists to facilitate mucosal colonization and penetration. Additionally, immunoglobulin A (IgA) proteases promote bacterial colonization in the presence of neutralizing secretory IgA through selective cleavage of the heavily O-glycosylated hinge region. In this review, we summarize families of O-glycoproteases and IgA proteases, discuss known structural features, and review applications of these enzymes to glycobiology.

The Synergistic Effects of Polysaccharides and Ginsenosides From American Ginseng (Panax quinquefolius L.) Ameliorating Cyclophosphamide-Induced Intestinal Immune Disorders and Gut Barrier Dysfunctions Based on Microbiome-Metabolomics Analysis

Cyclophosphamide (CTX), used in cancer chemotherapy, a high dose of which would cause immunosuppressive effect and intestinal mucosa damage. American ginseng (Panax quinquefolius L.) has a long history of functional food use for immunological disorder, colitis, cancer, and so on. This study aimed to illustrate the underlying mechanism of American ginseng’s immunomodulatory effect in CTX-induced mice. In this study, all groups of American ginseng (American ginseng polysaccharide [AGP], American ginseng ginsenoside [AGG], co-treated with American ginseng polysaccharide and ginsenoside [AGP_AGG]) have relieve the immune disorder by reversing the lymphocyte subsets ratio in spleen and peripheral blood, as well as stimulating CD4⁺T cells and IgA-secreting cells in small intestine. These three treatment groups, especially AGP_AGG co-treated group recovered the intestine morphology that up-regulated villus height (VH)/crypt depth (CD) ratio, areas of mucins expression, quantity of goblet cells, and expression of tight junction proteins (ZO-1, occludin). Importantly, the microbiome-metabolomics analysis was applied in this study to illustrate the possible immuno-modulating mechanism. The synergistic effect of polysaccharides and ginsenosides (AGP_AGG group) restored the gut microbiota composition and increased various beneficial mucosa-associated bacterial taxa Clostridiales, Bifidobacterium, and Lachnospiraceae, while decreased harmful bacteria Escherichia-Shigella and Peptococcaceae. Also, AGP_AGG group altered various fecal metabolites such as uric acid, xanthurenic acid, acylcarnitine, 9,10-DHOME, 13-HDoHE, LysoPE15:0, LysoPC 16:0, LysoPI 18:0, and so on, that associated with immunometabolism or protective effect of gut barrier. These results suggest AG, particularly co-treated of polysaccharide and ginsenoside may be used as immunostimulants targeting microbiome-metabolomics axis to prevent CTX-induced side effects in cancer patients.

Health effects of dietary sulfated polysaccharides from seafoods and their interaction with gut microbiota

Various dietary sulfated polysaccharides (SPs) have been isolated from seafoods, including edible seaweeds and marine animals, and their health effects such as antiobesity and anti-inflammatory activities have attracted remarkable interest. Sulfate groups have been shown to play important roles in the bioactivities of these polysaccharides. Recent in vitro and in vivo studies have suggested that the biological effects of dietary SPs are associated with the modulation of the gut microbiota. Dietary SPs could regulate the gut microbiota structure and, accordingly, affect the production of bioactive microbial metabolites. Because of their differential chemical structures, dietary SPs may specifically affect the growth of certain gut microbiota and associated metabolite production, which may contribute to variable health effects. This review summarizes the latest findings on the types and structural characteristics of SPs, the effects of different processing techniques on the structural characteristics and health effects of SPs, and the current understanding of the role of gut microbiota in the health effects of SPs. These findings might help in better understanding the mechanism of the health effects of SPs and provide a scientific basis for their application as functional food.

The anti-obesity effects exerted by different fractions of Artemisia sphaerocephala Krasch polysaccharide in diet-induced obese mice

Artemisia sphaerocephala Krasch polysaccharide (ASKP) consists of two main fractions, 60P (molecular weight at 551 kDa) and 60S (molecular weight at 39 kDa). The anti-obesity effects of ASKP and its two fractions were investigated in high-fat-diet-fed mice and showed similar capability in efficiently preventing the development of obesity. The final body weight and body weight gain of obesity mice model were reduced by 12.44% and 35.33% by ASKP, 10.63% and 34.35% by 60P, and 7.82% and 20.04% by 60S. They also showed similar efficiency to ameliorate dyslipidemia, systematic inflammation, and gut dysbiosis. The colonic genes of barrier integrity were significantly upregulated and the genes of hepatic lipid metabolism and that of colonic inflammatory response were suppressed. They attenuated the gut dysbiosis in obese mice, such as the significant enrichment of beneficial genera (Bifidobacterium and Olsenella) and suppression of harmful ones (Mucispirillum and Helicobacter). Significant enrichment of carbohydrate metabolism associated with the promotion of short-chain fatty acid production and decrease of the metabolisms related to obesity and gut dysbiosis (valine, leucine, and isoleucine biosynthesis, and nitrogen metabolism) were also observed by the administration of ASKP, 60P, and 60S. Overall, these polysaccharides showed potential in acting as prebiotics in preventing high-fat-diet-induced obesity.

Natural resources to control COVID-19: could lactoferrin amend SARS-CoV-2 infectivity?

The world population is still facing the second wave of the COVID-19 pandemic. Such a challenge requires complicated tools to control, namely vaccines, effective cures, and complementary agents. Here we present one candidate for the role of an effective cure and/or complementary agent: lactoferrin. It is the cross-talking mediator between many organs/cellular systems in the body. It serves as a physiological, immunological, and anti-microbial barrier, and acts as a regulator molecule. Furthermore, lactoferrin has receptors on most tissues cells, and is a rich source for bioactive peptides, particularly in the digestive system. In the past months, in vitro and in vivo evidence has accumulated regarding lactoferrin's ability to control SARS-CoV-2 infectivity in different indicated scenarios. Also, lactoferrin or whey milk (of human or other mammal's origin) is a cheap, easily available, and safe agent, the use of which can produce promising results. Pharmaceutical and/or food supplementary formulas of lactoferrin could be particularly effective in controlling the gastrointestinal COVID-19-associated symptoms and could limit the fecal-oral viral infection transmission, through mechanisms that mimic that of norovirus infection control by lactoferrin via induction of intestinal innate immunity. This natural avenue may be effective not only in symptomatic patients, but could also be more helpful in asymptomatic patients as a main or adjuvant treatment.

Acceptive Immunity: The Role of Fucosylated Glycans in Human Host-Microbiome Interactions

The growth in the number of chronic non-communicable diseases in the second half of the past century and in the first two decades of the new century is largely due to the disruption of the relationship between the human body and its symbiotic microbiota, and not pathogens. The interaction of the human immune system with symbionts is not accompanied by inflammation, but is a physiological norm. This is achieved via microbiota control by the immune system through a complex balance of pro-inflammatory and suppressive responses, and only a disturbance of this balance can trigger pathophysiological mechanisms. This review discusses the establishment of homeostatic relationships during immune system development and intestinal bacterial colonization through the interaction of milk glycans, mucins, and secretory immunoglobulins. In particular, the role of fucose and fucosylated glycans in the mechanism of interactions between host epithelial and immune cells is discussed.

Health benefits of edible mushroom polysaccharides and associated gut microbiota regulation

Edible mushrooms have been an important part of the human diet for thousands of years, and over 100 varieties have been cultivated for their potential human health benefits. In recent years, edible mushroom polysaccharides (EMPs) have been studied for their activities against obesity, inflammatory bowel disease (IBD), and cancer. Particularly, accumulating evidence on the exact causality between these health risks and specific gut microbiota species has been revealed and characterized, and most of the beneficial health effects of EMPs have been associated with its reversal impacts on gut microbiota dysbiosis. This demonstrates the key role of EMPs in decreasing health risks through gut microbiota modulation effects. This review article compiles and summarizes the latest studies that focus on the health benefits and underlying functional mechanisms of gut microbiota regulation via EMPs. We conclude that EMPs can be considered a dietary source for the improvement and prevention of several health risks, and this review provides the theoretical basis and technical guidance for the development of novel functional foods with the utilization of edible mushrooms.

Side-by-side and exo-pitting degradation mechanism revealed from in vitro human fecal fermentation of granular starches

The in vitro fecal fermentation characteristics and microbiota responses to A- and B-type polymorphic starches as model (whole) foods enriched with resistant starch was investigated. Marked difference in fermentation rate as well as microbial genera was observed during fermentation, the degradation pattern as well as structural evolution during fermentation was almost similar. The final butyrate concentrations of both HAMS and PS (ca. 38 mM) were significantly higher than that of WMS (23 mM) and NMS (33 mM), which was associated with the increase of the relative abundance of Roseburia, Blautia, and Lachnospiraceae. A-type polymorphic starches, on the other hand had remarkably faster fermentation rate and promoted Megamonas. X-ray diffraction and size-exclusion chromatography of residual starch during the fermentation course demonstrated the "side-by-side" fermentation pattern. Based on the structural changes observed, we conclude that in vitro fecal fermentation of starch granules predominantly controlled by the surface features rather than the molecular and supra-molecular structure.

Comparative analysis of the gut microbiota cultured in vitro using a single colon versus a 3-stage colon experimental design

The importance of the gut microbiota in human health and disease progression makes it a target for research in both the biomedical and nutritional fields. To date, a number of in vitro systems have been designed to recapitulate the gut microbiota of the colon ranging in complexity from the application of a single vessel to cultivate the community in its entirety, to multi-stage systems that mimic the distinct regional microbial communities that reside longitudinally through the colon. While these disparate types of in vitro designs have been employed previously, information regarding similarities and differences between the communities that develop within was less defined. Here, a comparative analysis of the population dynamics and functional production of short-chain fatty acids (SCFAs) was performed using the gut microbiota of the same donor cultured using a single vessel and a 3-stage colon system. The results found that the single vessel communities maintained alpha diversity at a level comparable to the distal regions of the 3-stage colon system. Yet, there was a marked difference in the type and abundance of taxa, particularly between families Enterobacteriaceae, Bacteroidaceae, Synergistaceae, and Fusobacteriaceae. Functionally, the single vessel community produced significantly less SCFAs compared to the 3-stage colon system. These results provide valuable information on how culturing technique effects gut microbial composition and function, which may impact studies relying on the application of an in vitro strategy. This data can be used to justify experimental strategy and provides insight on the application of a simplified versus complex study design. KEY POINTS : • A mature gut microbiota community can be developed in vitro using different methods. • Beta diversity metrics are affected by the in vitro culturing method applied. • The type and amount of short-chain fatty acids differed between culturing methods.

In vitro digestion of polysaccharides: InfoGest protocol and use of small intestinal extract from rat

Starch, dextran, pectin and modified citrus pectin were subjected to intestinal digestion following InfoGest protocol and a rat small intestine extract (RSIE) treatment. Gastric stage did not show any modification in the structure of the carbohydrates, except for modified pectin. Regarding intestinal phases, starch was hydrolyzed by different ways, resulting in a complementary behavior between InfoGest and RSIE. Contrarily, digestion of dextran was only observed using RSIE. Similar situation occurred in the case of pectins with RSIE, obtaining a partial hydrolysis, especially in the modified citrus pectin. However, citrus pectin was the less prone to hydrolysis by enzymes. The results demonstrated that InfoGest method underestimates the significance of the carbohydrates hydrolysis at the small intestine, thus indicating that RSIE is a very reliable and useful method for a more realistic study of polysaccharides digestion.

Alleviating effects of noni fruit polysaccharide on hepatic oxidative stress and inflammation in rats under a high-fat diet and its possible mechanisms

Non-alcoholic fatty liver disease is associated with gut microbiota, oxidative stress, and inflammation. We aimed to investigate the possible mechanism by which noni fruit polysaccharide (NFP) improved hepatic oxidative stress and inflammation in rats under a high-fat diet (HFD) by modulating short-chain fatty acids (SCFAs), the intestinal barrier, and gut microbiota. Hepatic oxidative stress, inflammation, and gut dysbiosis in rats were induced through HFD feeding for 4 weeks, followed by intervention with NFP treatment (100 mg per kg bw) for 5 weeks. The results showed that NFP reduced body weight gain and improved lipid metabolism, hepatic oxidative stress, and inflammation in rats under a HFD. Aside from these beneficial effects, NFP positively affected the SCFA production and reversed the HFD-induced gut dysbiosis as indicated by improved microbiota diversity and composition. The levels of Lactobacillus, Ruminococcaceae_UCG_014, Parasutterella, [Eubacterium]_coprostanoligenes_group, and Ruminococcus_1 improved, whereas the levels of Prevotella_9, Collinsella, Bacteroides, and Turicibacter decreased. Furthermore, NFP maintained the colonic barrier integrity (increased the mRNA relative expression of CCL5, ZO-1, and occludin in the colon, and decreased the serum CCL5 level), and decreased the serum lipopolysaccharide level. Thus, NFP may modulate the gut microflora and SCFA production and reduce the permeability of the colonic barrier and metabolic endotoxemia, thereby alleviating hepatic oxidative stress and inflammation in rats under a HFD.

Effect of copper sulfate on the external microbiota of adult common snook (Centropomus undecimalis)

BACKGROUND

The environment exerts a strong influence on the fish external microbiota, with lower diversity and increased abundances of opportunistic bacterial groups characterizing cultured fish compared to their wild counterparts. Deviation from a healthy external microbiota structure has been associated with increased susceptibility to bacterial pathogens. Treatment of wild-caught broodstock with copper sulfate for the removal of external parasites is a common aquaculture practice. Despite the microbiota's importance to fish health, the effects of copper sulfate on mucosal bacterial communities and their ability to recover following this chemical treatment have not been examined. The skin microbiota of adult common snook was characterized from wild individuals (Wild), and wild-caught fish maintained in recirculating aquaculture systems (RAS) immediately following a month-long copper sulfate treatment (Captive-1), and then two-weeks (Captive-2) and 2 years (Captive-3) after cessation of copper treatment.

RESULTS

The skin microbiota of wild fish were characterized by high diversity and taxa including Synechocococcus, SAR11, and a member of the Roseobacter clade. Bacterial diversity decreased in Captive individuals during the 2-year sampling period. Captive fish harbored greater abundances of Firmicutes, which may reflect glycan differences between aquaculture and natural feeds. Bacterial taxa with copper resistance mechanisms and indicative of metal contamination were enriched in Captive-1 and Captive-2 fish. Vibrionaceae were dominant in Captive fish, particularly immediately and 2 weeks following copper treatment. Based on our observations and previous literature, our results suggest putatively beneficial taxa amass over time in captivity. Within 2 years, Captive individuals harbored Bacillus which contains numerous probiotic candidates and the complex carbon degraders of the family Saprospiraceae. Predicted butanoate metabolism exceeded that of Wild fish, and its reported roles in immunity and energy provision suggest a prebiotic effect for fishes.

CONCLUSIONS

The mucosal microbiota contains bacterial taxa that may act as bioindicators of environmental pollution. Increases in mutualistic groups indicate a return to a beneficial skin microbiota following copper sulfate treatment. Our data also suggests that vastly different taxa, influenced by environmental conditions, can be associated with adult fish without noticeable health impairment, perhaps due to establishment of various mutualists to maintain fish mucosal health.

Modulating the Gut Microbiota of Humans by Dietary Intervention with Plant Glycans

The human colon contains a community of microbial species, mostly bacteria, which is often referred to as the gut microbiota. The community is considered essential to human well-being by conferring additional energy-harvesting capacity, niche exclusion of pathogens, and molecular signaling activities that are integrated into human physiological processes. Plant polysaccharides (glycans, dietary fiber) are an important source of carbon and energy that supports the maintenance and functioning of the gut microbiota. Therefore, the daily quantity and quality of plant glycans consumed by the human host have the potential to influence health. Members of the gut microbiota differ in ability to utilize different types of plant glycans. Dietary interventions with specific glycans could modulate the microbiota, counteracting ecological perturbations that disrupt the intricate relationships between microbiota and host (dysbiosis). This review considers prospects and research options for modulation of the gut microbiota by the formulation of diets that, when consumed habitually, would correct dysbiosis by building diverse consortia that boost functional resilience. Traditional "prebiotics" favor bifidobacteria and lactobacilli, whereas dietary mixtures of plant glycans that are varied in chemical complexity would promote high-diversity microbiotas. It is concluded that research should aim at improving knowledge of bacterial consortia that, through shared nourishment, degrade and ferment plant glycans. The consortia may vary in composition from person to person, but functional outputs will be consistent in a given context because of metabolic redundancy among bacteria. Thus, the individuality of gut microbiotas could be encompassed, functional resilience encouraged, and correction of dysbiosis achieved.

Comparison of Fecal Microbiota of Horses Suffering from Atypical Myopathy and Healthy Co-Grazers

Equine atypical myopathy (AM) is caused by hypoglycin A (HGA) and methylenecyclopropylglycine (MCPG) intoxication resulting from the ingestion of seeds or seedlings of some Acer tree species. Interestingly, not all horses pasturing in the same toxic environment develop signs of the disease. In other species, it has been shown that the intestinal microbiota has an impact on digestion, metabolism, immune stimulation and protection from disease. The objective of this study was to characterize and compare fecal microbiota of horses suffering from AM and healthy co-grazers. Furthermore, potential differences in fecal microbiota regarding the outcome of diseased animals were assessed. This prospective observational study included 59 horses with AM (29 survivors and 30 non-survivors) referred to three Belgian equine hospitals and 26 clinically healthy co-grazers simultaneously sharing contaminated pastures during spring and autumn outbreak periods. Fresh fecal samples (rectal or within 30 min of defecation) were obtained from all horses and bacterial taxonomy profiling obtained by 16S amplicon sequencing was used to identify differentially distributed bacterial taxa between AM-affected horses and healthy co-grazers. Fecal microbial diversity and evenness were significantly (p < 0.001) higher in AM-affected horses as compared with their non-affected co-grazers. The relative abundance of families Ruminococcaceae, Christensenellaceae and Akkermansiaceae were higher (p ≤ 0.001) whereas those of the Lachnospiraceae (p = 0.0053), Bacteroidales (p < 0.0001) and Clostridiales (p = 0.0402) were lower in horses with AM, especially in those with a poor prognosis. While significant shifts were observed, it is still unclear whether they result from the disease or might be involved in the onset of disease pathogenesis.

Mechanism of Intestinal Flora and Proteomics on Regulating Immune Function of Durio zibethinus Rind Polysaccharide

In this study, cyclophosphamide was injected intraperitoneally to establish an immunosuppressive mouse model to study the immune regulating effects of Durio zibethinus Murr rind polysaccharide (DZMP) through proteomics and intestinal flora. The results showed that the thymus and spleen indexes of the high-dose DZMP (200 mg/kg) group were significantly increased, and the tissue structure of the spleen was improved compared with the model group ( $P<0.01$ ). The contents of IL-2, IL-4, IL-6, and TNF-α in the high-dose group of DZMP were significantly increased ( $P<0.001$ ). Activities of acid phosphatase (ACP), lactate dehydrogenase (LDH), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) were increased in serum ( $P<0.01$ ). In the liver, catalase (CAT) activity was increased ( $P<0.001$ ) while the malondialdehyde (MDA) content was decreased and immune activity was increased ( $P<0.001$ ). Proteomics studies showed that the drug group could significantly increase the low-affinity immunoglobulin gamma Fc receptor III (FcγRIII) protein and protein kinase C-α (PKC-α) compared with the model group ( $P<0.001$ ). In addition, the result showed that those proteins were likely involved in the regulation of the metabolic pathways of autoimmune thyroid disease, Staphylococcus aureus infection, and NF-κB signaling pathway. Intestinal microbial studies showed that short-chain fatty acid (SCFA) content was increased as well as the relative abundance of beneficial bacteria Akkermansia, Bacteroides, and Paraprevotella, while the relative abundance of Ruminococcus and Oscillospira was decreased compared with the model group ( $P<0.001$ ). The results showed that DZMP might play a beneficial role in immune regulation by improving intestinal flora.