Ferriphaselus amnicola strain GF-20, a new iron- and thiosulfate-oxidizing bacterium isolated from a hard rock aquifer.

Ferriphaselus amnicola GF-20 is the first Fe-oxidizing bacterium isolated from the continental subsurface. It was isolated from groundwater circulating at 20 m depth in the fractured-rock catchment observatory of Guidel-Ploemeur (France). Strain GF-20 is a neutrophilic, iron- and thiosulfate-oxidizer and grows autotrophically. The strain shows a preference for low oxygen concentrations, which suggests an adaptation to the limiting oxygen conditions of the subsurface. It produces extracellular stalks and dreads when grown with Fe(II) but does not secrete any structure when grown with thiosulfate. Phylogenetic analyses and genome comparisons revealed that strain GF-20 is affiliated with the species F. amnicola and is strikingly similar to F. amnicola strain OYT1, which was isolated from a groundwater seep in Japan. Based on the phenotypic and phylogenetic characteristics, we propose that GF-20 represents a new strain within the species F. amnicola.

Gut microbiota-derived short-chain fatty acids promote prostate cancer progression via inducing cancer cell autophagy and M2 macrophage polarization.

We have previously demonstrated abnormal gut microbial composition in castration-resistant prostate cancer (CRPC) patients, here we revealed the mechanism of gut microbiota-derived short-chain fatty acids (SCFAs) as a mediator linking CRPC microbiota dysbiosis and prostate cancer (PCa) progression. By using transgenic TRAMP mouse model, PCa patient samples, in vitro PCa cell transwell and macrophage recruitment assays, we examined the effects of CRPC fecal microbiota transplantation (FMT) and SCFAs on PCa progression. Our results showed that FMT with CRPC patients' fecal suspension increased SCFAs-producing gut microbiotas such as Ruminococcus, Alistipes, Phascolarctobaterium in TRAMP mice, and correspondingly raised their gut SCFAs (acetate and butyrate) levels. CRPC FMT or SCFAs supplementation significantly accelerated mice's PCa progression. In vitro, SCFAs enhanced PCa cells migration and invasion by inducing TLR3-triggered autophagy that further activated NF-κB and MAPK signalings. Meanwhile, autophagy of PCa cells released higher level of chemokine CCL20 that could reprogramme the tumor microenvironment by recruiting more macrophage infiltration and simultaneously polarizing them into M2 type, which in turn further strengthened PCa cells invasiveness. Finally in a cohort of 362 PCa patients, we demonstrated that CCL20 expression in prostate tissue was positively correlated with Gleason grade, pre-operative PSA, neural/seminal vesical invasion, and was negatively correlated with post-operative biochemical recurrence-free survival. Collectively, CRPC gut microbiota-derived SCFAs promoted PCa progression via inducing cancer cell autophagy and M2 macrophage polarization. CCL20 could become a biomarker for prediction of prognosis in PCa patients. Intervention of SCFAs-producing microbiotas may be a useful strategy in manipulation of CRPC.

Effects of hemoglobin extracted from Tegillarca granosa on the gut microbiota in iron deficiency anemia mice.

Iron deficiency anemia (IDA) is a serious threat to the health of humans around the world. Tegillarca granosa (T. granosa) is considered as an excellent source of iron due to its abundant iron-binding protein hemoglobin. This study aimed to investigate the effects of hemoglobin from T. granosa on the gut microbiota and iron bioavailability in IDA mice. Compared to normal mice, IDA mice showed reduced microbiota diversity and altered relative abundance (reduced Muribaculaceae and increased Bacteroides). After 4 weeks of administration, hemoglobin restored the dysbiosis of the intestinal microbiota induced by IDA and decreased the Firmicutes/Bacteroidota ratio and the abundance of Proteobacteria. Analysis of the hemoglobin regeneration efficiency of mice treated with hemoglobin confirmed that hemoglobin exhibited high iron bioavailability, particularly at low-dose administration, suggesting that a small amount of hemoglobin from T. granosa markedly elevated the blood hemoglobin level in mice. These findings suggested that IDA could be alleviated by administration of hemoglobin with excellent iron bioavailability, and its therapeutic mechanism may be partially attributed to the regulation of the intestinal microbiota composition and relative abundance. These results indicated that T. granosa hemoglobin may be a promising iron supplement to treat IDA and promote the utilization of aquatic-derived proteins.

Fermentation of resistant starch from the starch-ferulic acid inclusion complex compared with high-amylose corn starch.

Fermentation of resistant starch from the starch-ferulic acid inclusion complex, one representative of the starch-polyphenol inclusion complex, was investigated in this study. It was found that this complex-based resistant starch, high-amylose corn starch and the mixture of ferulic acid and high-amylose corn starch were mainly utilized at the initial 6 h as indicated by the gas production and pH. Besides, the supplement of high-amylose corn starch, the mixture and the complex promoted production of short-chain fatty acids (SCFAs), reduced the ratio of Firmicutes/Bacteroidetes (F/B) and selectively stimulated the proliferation of some beneficial bacteria. Specifically, the production of SCFAs in the control and high-amylose starch, mixture and complex groups was 29.33 mM, 140.82 mM, 144.12 mM, and 167.4 mM after fermentation for 48 h, respectively. Moreover, the F/B ratio of those groups was 1.78, 0.78, 0.8 and 0.69, respectively. These results suggested that the supplement of the complex-based resistant starch led to the most SCFAs and the lowest F/B ratio (P < 0.05). Moreover, the complex group had the largest abundance of beneficial bacteria, including Bacteroides, Bifidobacterium and Lachnospiraceae_UCG-001 (P < 0.05). In summary, the resistant starch from the starch-ferulic acid inclusion complex exhibited stronger prebiotic activity than high-amylose corn starch and the mixture.

Pectin alleviates the pulmonary inflammatory response induced by PM2.5 from a pig house by modulating intestinal microbiota.

This study aimed to investigate whether dietary fiber pectin can alleviate PM2.5-induced pulmonary inflammation and the potential mechanism. PM2.5 samples were collected from a nursery pig house. The mice were divided into three groups: the control group, PM2.5 group and PM2.5 + pectin group. The mice in the PM2.5 group were intratracheally instilled with PM2.5 suspension twice a week for four consecutive weeks, and those in the PM2.5 + pectin group were subject to the same PM2.5 exposure, but fed with a basal diet supplemented with 5% pectin. The results showed that body weight and feed intake were not different among the treatments (p > 0.05). However, supplementation with pectin relieved PM2.5-induced pulmonary inflammation, presenting as slightly restored lung morphology, decreased mRNA expression levels of IL-1ß, IL-6 and IL-17 in the lung, decreased MPO content in bronchoalveolar lavage fluid (BLAF), and even decreased protein levels of IL-1ß and IL-6 in the serum (p < 0.05). Dietary pectin altered the composition of the intestinal microbiota, increasing the relative abundance of Bacteroidetes and decreasing the ratio of Firmicutes/Bacteroidetes. At the genus level, short-chain fatty acid (SCFA)-producing bacteria, such as Bacteroides, Anaerotruncus, Prevotella 2, Parabacteroides, Ruminococcus 2 and Butyricimonas, were enriched in the PM2.5 +pectin group. Accordingly, dietary pectin increased the concentrations of SCFAs, including acetate, propionate, butyrate and valerate, in mice. In conclusion, dietary fermentable fiber pectin can relieve PM2.5-induced pulmonary inflammation via alteration of intestinal microbiota composition and SCFA production. This study provides a new insight into reducing the health risk associated with PM2.5 exposure.

Iron Deficiency Modulates Metabolic Landscape of Bacteroidetes Promoting Its Resilience during Inflammation.

Bacteria have to persist under low iron conditions in order to adapt to the nutritional immunity of a host. Since the knowledge of iron stimulon of Bacteroidetes is sparse, we examined oral (Porphyromonas gingivalis and Prevotella intermedia) and gut (Bacteroides thataiotaomicron) representatives for their ability to adapt to iron deplete and iron replete conditions. Our transcriptomics and comparative genomics analysis show that many iron-regulated mechanisms are conserved within the phylum. They include genes upregulated in low iron, as follows: fldA (flavodoxin), hmu (hemin uptake operon), and loci encoding ABC transporters. Downregulated genes were frd (ferredoxin), rbr (rubrerythrin), sdh (succinate dehydrogenase/fumarate reductase), vor (oxoglutarate oxidoreductase/dehydrogenase), and pfor (pyruvate:ferredoxin/flavodoxin oxidoreductase). Some genus-specific mechanisms, such as the sus of B. thetaiotaomicron coding for carbohydrate metabolism and the xusABC coding for xenosiderophore utilization were also identified. While all bacteria tested in our study had the nrfAH operon coding for nitrite reduction and were able to reduce nitrite levels present in culture media, the expression of the operon was iron dependent only in B. thetaiotaomicron. It is noteworthy that we identified a significant overlap between regulated genes found in our study and the B. thetaiotaomicron colitis study (W. Zhu, M. G. Winter, L. Spiga, E. R. Hughes et al., Cell Host Microbe 27:376-388, 2020, http://dx.doi.org/10.1016/j.chom.2020.01.010). Many of those commonly regulated genes were also iron regulated in the oral bacterial genera. Overall, this work points to iron being the master regulator enabling bacterial persistence in the host and paves the way for a more generalized investigation of the molecular mechanisms of iron homeostasis in Bacteroidetes. IMPORTANCE Bacteroidetes are an important group of anaerobic bacteria abundant both in the oral and gut microbiomes. Although iron is a required nutrient for most living organisms, the molecular mechanisms of adaptation to the changing levels of iron are not well known in this group of bacteria. We defined the iron stimulon of Bacteroidetes by examination of the transcriptomic response of Porphyromonas gingivalis and Prevotella intermedia (both belong to the oral microbiome) and Bacteroidetes thetaiotaomicron (belongs to the gut microbiome). Our results indicate that many of the iron-regulated operons are shared among the three genera. Furthermore, using bioinformatics analysis, we identified a significant overlap between our in vitro studies and transcriptomic data derived from a colitis study, thus underscoring the biological significance of our work. Defining the iron-dependent stimulon of Bacteroidetes can help to identify the molecular mechanisms of iron-dependent regulation as well as better understand the persistence of the anaerobes in the human host.

The gut microbiome: a core regulator of metabolism.

The human body is inhabited by numerous bacteria, fungi, and viruses, and each part has a unique microbial community structure. The gastrointestinal tract harbors approximately 100 trillion strains comprising more than 1000 bacterial species that maintain symbiotic relationships with the host. The gut microbiota consists mainly of the phyla Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Of these, Firmicutes and Bacteroidetes constitute 70-90% of the total abundance. Gut microbiota utilize nutrients ingested by the host, interact with other bacterial species, and help maintain healthy homeostasis in the host. In recent years, it has become increasingly clear that a breakdown of the microbial structure and its functions, known as dysbiosis, is associated with the development of allergies, autoimmune diseases, cancers, and arteriosclerosis, among others. Metabolic diseases, such as obesity and diabetes, also have a causal relationship with dysbiosis. The present review provides a brief overview of the general roles of the gut microbiota and their relationship with metabolic disorders.

Firmicutes/Bacteroidetes Ratio in the Gut Microbiota and IL-1ß, IL-6, IL-8, TLR2, TLR4, TLR5 Gene Expressions in Type 2 Diabetes.

BACKGROUND: The aim of this study was to determine the Firmicutes/Bacteroidetes ratio in the gut microbiota and IL-1ß, IL-6, IL-8, TLR2, TLR4 and TLR5 gene expression levels in the blood of adult type 2 diabetes (T2D) patients and compare it with that of adult nondiabetic healthy controls (HC). METHODS: Between May 2016 and April 2017, 99 T2D patients and 99 HCs were enrolled in the study. Bacteroidetes and Firmicutes levels were assessed from stool sample DNA and IL-1ß, IL-6, IL-8, TLR2, TLR4, and TLR5 gene expression levels assesed from blood sample RNA via qPCR from both T2D patients and healthy controls. RESULTS: The Firmicutes/Bacteroidetes ratio detected in the stool of type 2 diabetes patients was found to be higher with a statistically significant difference (p < 0.0001). Gene expression levels of IL-1ß, IL-6, IL-8, TLR2, TLR4, and TLR5 were found to be upregulated. CONCLUSIONS: The highest upregulation was detected in IL-6 with 11 fold in T2D patients comparing with HCs. F/B ratio and gene expression levels were elevated in T2D patients. Firmicutes were positively correlated with studied gene expressions. A better understanding of the complex interaction between gut microbiota, environment, and diabetes will allow for more effective prevention and treatment strategies for T2D.

Biochemical characterization of the first step in sulfonolipid biosynthesis in Alistipes finegoldii.

Sulfonolipids are unusual lipids found in the outer membranes of Gram-negative bacteria in the phylum Bacteroidetes. Sulfonolipid and its deacylated derivative, capnine, are sulfur analogs of ceramide-1-phosphate and sphingosine-1-phosphate, respectively; thus, sulfonolipid biosynthesis is postulated to be similar to the sphingolipid biosynthetic pathway. Here, we identify the first enzyme in sulfonolipid synthesis in Alistipes finegoldii as the product of the alfi_1224 gene, cysteate acyl-acyl carrier protein (ACP) transferase (SulA). We show SulA catalyzes the condensation of acyl-ACP and cysteate (3-sulfo-alanine) to form 3-ketocapnine. Acyl-CoA is a poor substrate. We show SulA has a bound pyridoxal phosphate (PLP) cofactor that undergoes a spectral redshift in the presence of cysteate, consistent with the transition of the lysine-aldimine complex to a substrate-aldimine complex. Furthermore, the SulA crystal structure shows the same prototypical fold found in bacterial serine palmitoyltransferases (Spts), enveloping the PLP cofactor bound to Lys251. We observed the SulA and Spt active sites are identical except for Lys281 in SulA, which is an alanine in Spt. Additionally, SulA(K281A) is catalytically inactive but binds cysteate and forms the external aldimine normally, highlighting the structural role of the Lys281 side chain in walling off the active site from bulk solvent. Finally, the electropositive groove on the protein surface adjacent to the active site entrance provides a landing pad for the electronegative acyl-ACP surface. Taken together, these data identify the substrates, products, and mechanism of SulA, the PLP-dependent condensing enzyme that catalyzes the first step in sulfonolipid synthesis in a gut commensal bacterium.

Bioactive natural products from Bacteroidetes.

Covering: up to end of January 2022Bacteria representing the phylum Bacteroidetes produce a diverse range of natural products, including polyketides, peptides and lactams. Here, we discuss unique aspects of the bioactive compounds discovered thus far, and the corresponding biosynthetic pathways if known, providing a comprehensive overview of the Bacteroidetes as a natural product reservoir.

Nitrite as a causal factor for nitrate-dependent anaerobic corrosion of metallic iron induced by Prolixibacter strains.

Microbially influenced corrosion (MIC) may contribute significantly to overall corrosion risks, especially in the gas and petroleum industries. In this study, we isolated four Prolixibacter strains, which belong to the phylum Bacteroidetes, and examined their nitrate respiration- and Fe0 -corroding activities, together with two previously isolated Prolixibacter strains. Four of the six Prolixibacter strains reduced nitrate under anaerobic conditions, while the other two strains did not. The anaerobic growth of the four nitrate-reducing strains was enhanced by nitrate, which was not observed in the two strains unable to reduce nitrate. When the nitrate-reducing strains were grown anaerobically in the presence of Fe0 or carbon steel, the corrosion of the materials was enhanced by more than 20-fold compared to that in aseptic controls. This enhancement was not observed in cultures of the strains unable to reduce nitrate. The oxidation of Fe0 in the anaerobic cultures of nitrate-reducing strains occurred concomitantly with the formation of nitrite. Since nitrite chemically oxidized Fe0 under anaerobic and aseptic conditions, the corrosion of Fe0 - and carbon steel by the nitrate-reducing Prolixibacter strains was deduced to be mainly enhanced via the biological reduction of nitrate to nitrite, followed by the chemical oxidation of Fe0 to Fe2+ and Fe3+ coupled to the reduction of nitrite.

Microbiota regulate innate immune signaling and protective immunity against cancer.

Microbiota play critical roles in regulating colitis and colorectal cancer (CRC). However, it is unclear how the microbiota generate protective immunity against these disease states. Here, we find that loss of the innate and adaptive immune signaling molecule, TAK1, in myeloid cells (Tak1ΔM/ΔM) yields complete resistance to chemical-induced colitis and CRC through microbiome alterations that drive protective immunity. Tak1ΔM/ΔM mice exhibit altered microbiota that are critical for resistance, with antibiotic-mediated disruption ablating protection and Tak1ΔM/ΔM microbiota transfer conferring protection against colitis or CRC. The altered microbiota of Tak1ΔM/ΔM mice promote IL-1ß and IL-6 signaling pathways, which are required for induction of protective intestinal Th17 cells and resistance. Specifically, Odoribacter splanchnicus is abundant in Tak1ΔM/ΔM mice and sufficient to induce intestinal Th17 cell development and confer resistance against colitis and CRC in wild-type mice. These findings identify specific microbiota strains and immune mechanisms that protect against colitis and CRC.

Effects of Anthocyanin on Intestinal Health: A Systematic Review.

Intestinal health relies on the association between the mucosal immune system, intestinal barrier and gut microbiota. Bioactive components that affect the gut microbiota composition, epithelial physical barrier and intestinal morphology were previously studied. The current systematic review evaluated evidence of anthocyanin effects and the ability to improve gut microbiota composition, their metabolites and parameters of the physical barrier; this was conducted in order to answer the question: "Does food source or extract of anthocyanin promote changes on intestinal parameters?". The data analysis was conducted following the PRISMA guidelines with the search performed at PubMed, Cochrane and Scopus databases for experimental studies, and the risk of bias was assessed by the SYRCLE tool. Twenty-seven studies performed in animal models were included, and evaluated for limitations in heterogeneity, methodologies, absence of information regarding allocation process and investigators' blinding. The data were analyzed, and the anthocyanin supplementation demonstrated positive effects on intestinal health. The main results identified were an increase of Bacteroidetes and a decrease of Firmicutes, an increase of short chain fatty acids production, a decrease of intestinal pH and intestinal permeability, an increase of the number of goblet cells and tight junction proteins and villi improvement in length or height. Thus, the anthocyanin supplementation has a potential effect to improve the intestinal health. PROSPERO (CRD42020204835).

Enrichment of novel Verrucomicrobia, Bacteroidetes, and Krumholzibacteria in an oxygen-limited methane- and iron-fed bioreactor inoculated with Bothnian Sea sediments.

Microbial methane oxidation is a major biofilter preventing larger emissions of this powerful greenhouse gas from marine coastal areas into the atmosphere. In these zones, various electron acceptors such as sulfate, metal oxides, nitrate, or oxygen can be used. However, the key microbial players and mechanisms of methane oxidation are poorly understood. In this study, we inoculated a bioreactor with methane- and iron-rich sediments from the Bothnian Sea to investigate microbial methane and iron cycling under low oxygen concentrations. Using metagenomics, we investigated shifts in microbial community composition after approximately 2.5 years of bioreactor operation. Marker genes for methane and iron cycling, as well as respiratory and fermentative metabolism, were identified and used to infer putative microbial metabolism. Metagenome-assembled genomes representing novel Verrucomicrobia, Bacteroidetes, and Krumholzibacteria were recovered and revealed a potential for methane oxidation, organic matter degradation, and iron cycling, respectively. This work brings new hypotheses on the identity and metabolic versatility of microorganisms that may be members of such functional guilds in coastal marine sediments and highlights that microorganisms potentially composing the methane biofilter in these sediments may be more diverse than previously appreciated.

Transport and Polymerization of Porphyromonas gingivalis Type V Pili.

Adhesive pili (or fimbriae) in bacteria are classified into five types, among which type V pili have been most recently described. Type V pili differ from other pili types with respect to transport mechanism, structure, and pilin synthesis. Genes of type V pili are restricted to the phylum Bacteroidetes. Protein subunits that compose type V pili are transported to the cell surface as lipoprotein precursors and then polymerized into a pilus through a strand-exchange mechanism, which is demonstrated by several experiments, including palmitic acid labeling and Cys-Cys cross-linking analysis. Here, we describe the use of these methods to analyze type V pili.

Microbial Butyrate Synthesis Indicates Therapeutic Efficacy of Azathioprine in IBD Patients.

BACKGROUND AND AIMS: The microbial ecosystem seems to be an important player for therapeutic intervenption in inflammatory bowel disease [IBD]. We assessed longitudinal microbiome changes in IBD patients undergoing therapy with either azathioprine [AZA] or anti-tumour necrosis factor [anti-TNF] antibodies. We predicted the metabolic microbial community exchange and linked it to clinical outcome. METHODS: Faecal and blood samples were collected from 65 IBD patients at baseline and after 12 and 30 weeks on therapy. Clinical remission was defined as Crohn's Disease Activity Index [CDAI] < 150 in Crohn´s disease [CD], partial Mayo score <2 in ulcerative colitis [UC], and faecal calprotectin values <150 µg/g and C-reactive protein <5 mg/dl. 16S rRNA amplicon sequencing was performed. To predict microbial community metabolic processes, we constructed multispecies genome-scale metabolic network models. RESULTS: Paired Bray-Curtis distance between baseline and follow-up time points was significantly different for UC patients treated with anti-TNF antibodies. Longitudinal changes in taxa composition at phylum level showed a significant decrease of Proteobacteria and an increase of Bacteroidetes in CD patients responding to both therapies. At family level, Lactobacilli were associated with persistent disease and Bacteroides abundance with remission in CD. In-silico simulations of microbial metabolite exchange predicted a 1.7-fold higher butyrate production capacity of patients in remission compared with patients without remission [p = 0.041]. In this model, the difference in butyrate production between patients in remission and patients without remission was most pronounced in the CD group treated with AZA [p = 0.008]. CONCLUSIONS: In-silico simulation identifies microbial butyrate synthesis predictive of therapeutic efficacy in IBD.

Dietary cellulose induces anti-inflammatory immunity and transcriptional programs via maturation of the intestinal microbiota.

Although it is generally accepted that dietary fiber is health promoting, the underlying immunological and molecular mechanisms are not well defined, especially with respect to cellulose, the most ubiquitous dietary fiber. Here, the impact of dietary cellulose on intestinal microbiota, immune responses and gene expression in health and disease was examined. Lack of dietary cellulose disrupted the age-related diversification of the intestinal microbiota, which subsequently remained in an immature state. Interestingly, one of the most affected microbial genera was Alistipes which is equipped with enzymes to degrade cellulose. Absence of cellulose changed the microbial metabolome, skewed intestinal immune responses toward inflammation, altered the gene expression of intestinal epithelial cells and mice showed increased sensitivity to colitis induction. In contrast, mice with a defined microbiota including A. finegoldii showed enhanced colonic expression of intestinal IL-22 and Reg3γ restoring intestinal barrier function. This study supports the epidemiological observations and adds a causal explanation for the health promoting effects of the most common biopolymer on earth.

Clostridium butyricum modulates gut microbiota and reduces colitis associated colon cancer in mice.

We investigate the effects of Clostridium butyricum(CB) on gut microbiota and colitis associated colon cancer(CAC) in mice.6-8 weeks old C57BL/6 mice were randomly divided into control, azoxymethane (AOM) + dextran sodium sulphate (DSS) and AOM + DSS + CB groups. Mice in the latter two groups received an intraperitoneal injection of AOM (12.5 mg/kg), followed by three cycles of DSS diluted in water (2.5% w/v). Mice in treatment group received CB (2 × 108 CFU in 200 ul normal saline) by gavage administration three times one week. Microbiota composition was assessed by 16S rRNA high-throughput sequencing. Colon samples were collected to examine severity of colitis and tumorigenesis. Cytokines including TNF-a, IL-6 and Cyclo-oxygenase-2 (COX-2) were detected by RT-qPCR. Expression of Bcl-2, Bax and the state of components of NF-κB signaling pathway were detected by western blot. The results revealed that CB regulated structure of intestinal flora and changed the microbial composition; decreased Firmicutes/ Bacteroidetes ratio in phylum level and increased the relative abundance of probiotics; decreased colitis, decreased incidence and size of colorectal cancer(CRC) and increased apoptosis of tumor cells; decreased cytokines including TNF-a and IL-6; decreased level of COX-2; decreased phosphorylation of NF-κB; decreased level of Bcl-2 and increased expression of Bax. In conclusion, CB could regulate structure and composition of gut microbiota and reduces colitis associated colon cancer in mice, the mechanism may be inhibiting NF-κB pathway and promoting apoptosis.

The Genus Alistipes: Gut Bacteria With Emerging Implications to Inflammation, Cancer, and Mental Health.

Alistipes is a relatively new genus of bacteria isolated primarily from medical clinical samples, although at a low rate compared to other genus members of the Bacteroidetes phylum, which are highly relevant in dysbiosis and disease. According to the taxonomy database at The National Center for Biotechnology Information, the genus consists of 13 species: Alistipes finegoldii, Alistipes putredinis, Alistipes onderdonkii, Alistipes shahii, Alistipes indistinctus, Alistipes senegalensis, Alistipes timonensis, Alistipes obesi, Alistipes ihumii, Alistipes inops, Alistipes megaguti, Alistipes provencensis, and Alistipes massiliensis. Alistipes communis and A. dispar, and the subspecies A. Onderdonkii subspecies vulgaris (vs. onderdonkii subsp.) are the newest strains featured outside that list. Although typically isolated from the human gut microbiome various species of this genus have been isolated from patients suffering from appendicitis, and abdominal and rectal abscess. It is possible that as Alistipes spp. emerge, their identification in clinical samples may be underrepresented as novel MS-TOF methods may not be fully capable to discriminate distinct species as separate since it will require the upgrading of MS-TOF identification databases. In terms of pathogenicity, there is contrasting evidence indicating that Alistipes may have protective effects against some diseases, including liver fibrosis, colitis, cancer immunotherapy, and cardiovascular disease. In contrast, other studies indicate Alistipes is pathogenic in colorectal cancer and is associated with mental signs of depression. Gut dysbiosis seems to play a role in determining the compositional abundance of Alistipes in the feces (e.g., in non-alcoholic steatohepatitis, hepatic encephalopathy, and liver fibrosis). Since Alistipes is a relatively recent sub-branch genus of the Bacteroidetes phylum, and since Bacteroidetes are commonly associated with chronic intestinal inflammation, this narrative review illustrates emerging immunological and mechanistic implications by which Alistipes spp. correlate with human health.

Fish oil extracted from Coregonus peled improves obese phenotype and changes gut microbiota in a high-fat diet-induced mouse model of recurrent obesity.

Recurrent obesity is rapidly emerging as a public health problem. Previous studies have confirmed that fish oil supplementation can alleviate obesity in mice; however, the effect of fish oil on recurrent obesity remains unclear. In the present study, the modulatory effects of fish oil extracted from Coregonus peled on the phenotypes and gut microbiota of recurrent obese mice were evaluated by MRI, OGTT, and bioinformatics analysis. We found that fish oil supplementation could significantly reduce the body weight gain, net weight gain, body fat distribution, and glucose tolerance. In addition, the composition and structure of gut microbiota were significantly shifted toward those of the control group by fish oil treatment. Moreover, the relative abundance of gut microbiota, such as Bacteroidetes, Bacteroidia, Lachnospiraceae, and Bifidobacterium, was markedly responding to the rapid dietary changes between fish oil and high-fat diet. Overall, our results confirmed that the alleviation of recurrent obesity using fish oil supplementation might be modulated by altering the hysteretic behavior and memory-like function of gut microbiota. We proposed that further studies are needed to elucidate the modulation mechanism.