Microbial Cues Research Articles

HDAC3 integrates TGF-β and microbial cues to program tuft cell biogenesis and diurnal rhythms in mucosal immune surveillance.

The intestinal mucosal surface is directly exposed to daily fluctuations in food and microbes driven by 24-hour light and feeding cycles. Intestinal epithelial tuft cells are key sentinels that surveil the gut luminal environment, but how these cells are diurnally programmed remains unknown. Here, we show that histone deacetylase 3 (HDAC3) controls tuft cell specification and the diurnal rhythm of its biogenesis, which is regulated by the gut microbiota and feeding schedule. Disruption of epithelial HDAC3 decreases tuft cell numbers, impairing antihelminth immunity and norovirus infection. Mechanistically, HDAC3 functions noncanonically to activate transforming growth factor-β (TGF-β) signaling, which promotes rhythmic expression of Pou2f3, a lineage-defining transcription factor of tuft cells. Our findings reveal an environmental-epigenetic link that controls the diurnal differentiation of tuft cells and promotes rhythmic mucosal surveillance and immune responses in anticipation of exogenous challenges.

Microbial signatures and continuum in endometrial cancer and benign patients

BackgroundEndometrial cancer is a multifactorial disease with inflammatory, metabolic and potentially microbial cues involved in disease pathogenesis. The endometrial cancer microbiome has been poorly characterised so far and studies have often overestimated bacterial biomass due to lack of integration of appropriate contamination controls. There is also a scarcity of evidence on the functionality of microbial microenvironments in endometrial cancer. This work addresses that knowledge gap by interrogating the genuine, contamination-free microbial signatures in the female genital tract and rectum of women with endometrial cancer and the mechanistic role of microbiome on carcinogenic processes.ResultsHere we sampled different regions of the reproductive tract (vagina, cervix, endometrium, fallopian tubes and ovaries) and rectum of 61 patients (37 endometrial cancer; 24 benign controls). We performed 16S rRNA gene sequencing of the V1–V2 hypervariable regions and qPCR of the 16S rRNA gene to qualitatively and quantitatively assess microbial communities and used 3D benign and endometrial cancer organoids to evaluate the effect of microbial products of L. crispatus, which was found depleted in endometrial cancer patients following primary analysis, on endometrial cell proliferation and inflammation. We found that the upper genital tract of a subset of women with and without endometrial cancer harbour microbiota quantitatively and compositionally distinguishable from background contaminants. Endometrial cancer was associated with reduced cervicovaginal and rectal bacterial load together with depletion of Lactobacillus species relative abundance, including L. crispatus, increased bacterial diversity and enrichment of Porphyromonas, Prevotella, Peptoniphilus and Anaerococcus in the lower genital tract and endometrium. Treatment of benign and malignant endometrial organoids with L. crispatus conditioned media exerted an anti-proliferative effect at high concentrations but had minimal impact on cytokine and chemokine profiles.ConclusionsOur findings provide evidence that the upper female reproductive tract of some women contains detectable levels of bacteria, the composition of which is associated with endometrial cancer. Whether this is a cause or consequence of cancer pathophysiology and what is the functional significance of this finding remain to be elucidated to guide future screening tools and microbiome-based therapeutics.7srhokZSHNZrvrGZNmjDS4Video

Endothelial sensing of AHR ligands regulates intestinal homeostasis

Endothelial cells line the blood and lymphatic vasculature, and act as an essential physical barrier, control nutrient transport, facilitate tissue immunosurveillance and coordinate angiogenesis and lymphangiogenesis1,2. In the intestine, dietary and microbial cues are particularly important in the regulation of organ homeostasis. However, whether enteric endothelial cells actively sense and integrate such signals is currently unknown. Here we show that the aryl hydrocarbon receptor (AHR) acts as a critical node for endothelial cell sensing of dietary metabolites in adult mice and human primary endothelial cells. We first established a comprehensive single-cell endothelial atlas of the mouse small intestine, uncovering the cellular complexity and functional heterogeneity of blood and lymphatic endothelial cells. Analyses of AHR-mediated responses at single-cell resolution identified tissue-protective transcriptional signatures and regulatory networks promoting cellular quiescence and vascular normalcy at steady state. Endothelial AHR deficiency in adult mice resulted in dysregulated inflammatory responses and the initiation of proliferative pathways. Furthermore, endothelial sensing of dietary AHR ligands was required for optimal protection against enteric infection. In human endothelial cells, AHR signalling promoted quiescence and restrained activation by inflammatory mediators. Together, our data provide a comprehensive dissection of the effect of environmental sensing across the spectrum of enteric endothelia, demonstrating that endothelial AHR signalling integrates dietary cues to maintain tissue homeostasis by promoting endothelial cell quiescence and vascular normalcy.

Effects of bacterial composition and aquatic habitat metabolites on malaria vector larval availability in irrigated and non-irrigated sites of Homa Bay county, western Kenya.

Gravid Anopheles malaria vectors depend on both chemical and physical (including microbial) cues for selection of preferred habitats for oviposition. This study focused on assessing the effects of bacterial composition and habitat metabolites on malaria vector larval availability in irrigated and non-irrigated potential larval sources. Water samples were collected from larval positive and negative habitats in the irrigated and non- irrigated areas of Homa Bay county. Bacteria cultured from the water samples were subjected to Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) for species identification. DNA was extracted from the colonies and polymerase chain reaction (PCR) and sequencing done. Finally, the metabolite composition of larval positive and negative habitats was determined. MALDI-TOF MS results revealed that Bacillus was the only genera identified from larval sources in the non-irrigated zone. In the irrigated area, Shigella was the dominant genera (47%) while Escherichia coli was the abundant species (13/51). Of the sequenced isolates, 65% were Bacillus. Larvicidal isolates Brevibacillus brevis, Bacillus subtilis, and Exiguobacterium profundum were isolated and grouped with Bacillus mojavensis, Bacillus tequilensis, Bacillus stercoris, and Brevibacillus agri. Irrigated areas with larvae had reduced crude fat (0.01%) and protein content (0.13%) in comparison to those without larvae. In irrigated and non- irrigated areas, larval presence was evident in habitats with high total chlorophyll content (1.12 μg/g vs 0.81μg/g and 3.37 μg/g vs 0.82). Aquatic habitats with larvae in both irrigated and non-irrigated areas exhibited higher sugar concentration than habitats without larvae; however, when compared, non-irrigated areas with larvae had higher sugar concentration than similar habitats in irrigated areas. In addition, substantial concentrations of Manganese, Calcium, and Copper were found in aquatic habitats containing larvae in both irrigated and non-irrigated areas. These results allow for prospective examination as potential larvicidal or adulticidal agents and could be considered when designing potential vector control interventions.

Microbial cues stimulate linear growth in undernourished mice.

Microbial cues stimulate linear growth in undernourished mice.

Comparative Genomic Insights into Bacterial Induction of Larval Settlement and Metamorphosis in the Upside-Down Jellyfish Cassiopea.

Bacteria are important mediators of the larval transition from pelagic to benthic environments for marine organisms. Bacteria can therefore dictate species distribution and success of an individual. Despite the importance of marine bacteria to animal ecology, the identity of inductive microbes for many invertebrates are unknown. Here, we report the first successful isolation of bacteria from natural substrates capable of inducing settlement and metamorphosis of the planula larvae stage of a true jellyfish, the upside-down jellyfish Cassiopea xamachana. Inductive bacteria belonged to multiple phyla, with various capacity to induce settlement and metamorphosis. The most inductive isolates belonged to the genus Pseudoalteromonas, a marine bacterium known to induce the pelago-benthic transition in other marine invertebrates. In sequencing the genome of the isolated Pseudoalteromonas and a semiinductive Vibrio, we found biosynthetic pathways previously implicated in larval settlement were absent in Cassiopea inducing taxa. We instead identified other candidate biosynthetic gene clusters involved in larval metamorphosis. These findings could provide hints to the ecological success of C. xamachana compared to sympatric congeneric species within mangrove environments and provide avenues to investigate the evolution of animal-microbe interactions. IMPORTANCE The pelagic to benthic transition for the larvae of many marine invertebrate species are thought to be triggered by microbial cues. The microbial species and exact cue that initiates this transition remains unknown for many animals. Here, we identify two bacterial species, a Pseudoalteromonas and a Vibrio, isolated from natural substrate that induce settlement and metamorphosis of the upside-down jellyfish Cassiopea xamachana. Genomic sequencing revealed both isolates lacked genes known to induce the life history transition in other marine invertebrates. Instead, we identified other gene clusters that may be important for jellyfish settlement and metamorphosis. This study is the first step to identifying the bacterial cue for C. xamachana, an ecologically important species to coastal ecosystems and an emerging model system. Understanding the bacterial cues provides insight into marine invertebrate ecology and evolution of animal-microbe interactions.

M cell maturation and cDC activation determine the onset of adaptive immune priming in the neonatal Peyer’s patch

Early-life immune development is critical to long-term host health. However, the mechanisms that determine the pace of postnatal immune maturation are not fully resolved. Here, we analyzed mononuclear phagocytes (MNPs) in small intestinal Peyer's patches (PPs), the primary inductive site of intestinal immunity. Conventional type 1 and 2 dendritic cells (cDC1 and cDC2) and RORgt+ antigen-presenting cells (RORgt+ APC) exhibited significant age-dependent changes in subset composition, tissue distribution, and reduced cell maturation, subsequently resulting in a lack in CD4+ Tcell priming during the postnatal period. Microbial cues contributed but could not fully explain the discrepancies in MNP maturation. Type I interferon (IFN) accelerated MNP maturation but IFN signaling did not represent the physiological stimulus. Instead, follicle-associated epithelium (FAE) M cell differentiation was required and sufficient to drive postweaning PP MNP maturation. Together, our results highlight the role of FAE M cell differentiation and MNP maturation in postnatal immune development.

Structure-function analysis of Lactiplantibacillus plantarum DltE reveals D-alanylated lipoteichoic acids as direct cues supporting Drosophila juvenile growth.

Metazoans establish mutually beneficial interactions with their resident microorganisms. However, our understanding of the microbial cues contributing to host physiology remains elusive. Previously, we identified a bacterial machinery encoded by the dlt operon involved in Drosophila melanogaster's juvenile growth promotion by Lactiplantibacillus plantarum. Here, using crystallography combined with biochemical and cellular approaches, we investigate the physiological role of an uncharacterized protein (DltE) encoded by this operon. We show that lipoteichoic acids (LTAs) but not wall teichoic acids are D-alanylated in Lactiplantibacillus plantarumNC8 cell envelope and demonstrate that DltE is a D-Ala carboxyesterase removing D-Ala from LTA. Using the mutualistic association of L. plantarumNC8 and Drosophila melanogaster as a symbiosis model, we establish that D-alanylated LTAs (D-Ala-LTAs) are direct cues supporting intestinal peptidase expression and juvenile growth in Drosophila. Our results pave the way to probing the contribution of D-Ala-LTAs to host physiology in other symbiotic models.

NF-κB Regulation by Gut Microbiota Decides Homeostasis or Disease Outcome During Ageing.

Human beings and their indigenous microbial communities have coexisted for centuries, which led to the development of co-evolutionary mechanisms of communication and cooperation. Such communication machineries are governed by sophisticated multi-step feedback loops, which typically begin with the recognition of microbes by pattern recognition receptors (PRRs), followed by a host transcriptional response leading to the release of effector molecules. Our gastrointestinal tract being the main platform for this interaction, a variety of host intestinal cells tightly regulate these loops to establish tolerance towards the microbial communities of the gut and maintain homeostasis. The transcription factor, nuclear factor kappa B (NF-κB) is an integral component of such a communication apparatus, which plays a critical role in determining the state of homeostasis or inflammation associated with dysbiosis in the host. Here we outline the crucial role of NF-κB in host response to microbial cues in the context of ageing and associated diseases.

246-LB: Neonatal Microbes Stimulate Beta-Cell Development

Newborns are exposed to environmental microbes that colonize the gut and increase in diversity during childhood to establish the resident microbiota. Concurrently, insulin-producing β-cells enter a postnatal window of proliferation and maturation. We found that germ-free animal models exhibit significant reductions in β-cell mass compared to their microbe-carrying counterparts, revealing a role for microbes in the establishment of these cells. By mining this unique source, we uncovered mechanisms of bacterially driven β-cell development. Neonatal mice given strategically timed doses of broad-spectrum antibiotics incurred lasting reductions in β-cell mass, revealing a critical period of microbial influence on β-cells. Though reconstituted with a normal microbiota after antibiotic treatment, as adults these animals had reduced glucose tolerance and insulin secretion, and were more susceptible to metabolic disease. Treatment of neonatal mice with selective antibiotics resulted in variations in β-cell mass, blood glucose, and insulin levels, suggesting unique bacterial taxa or products influence these traits. Sequencing revealed that distinct microbes were enriched within each antibiotic treatment, allowing us to identify candidate bacterial taxa that we show are sufficient to stimulate β-cell expansion and restore insulin function. Further, we have identified multiple islet associated cell types that respond to these microbial cues. Previously, we identified the bacterial protein, BefA, that directly stimulates β-cell proliferation, and we anticipate finding additional bacterial modulators of this important tissue. Reduced microbiota diversity can be predictive of diabetes in susceptible children, suggesting that early life microbial exposures are critical to prevent disease. Our results indicate loss of specific bacteria may result in reduced insulin production capacity prior to autoimmunity. If we can reinstate these lost microbes, we may be able to bolster the β-cell population against loss. Disclosure J. H. Hill: None. K. Guillemin: None. C. L. Murtaugh: None. J. Round: None. Funding Junior Diabetes Research Foundation (3-PDF-2019-747-A-N)

Marine biofilms: diversity, interactions and biofouling

Marine biofilms are ubiquitous in the marine environment. These complex microbial communities rapidly respond to environmental changes and encompass hugely diverse microbial structures, functions and metabolisms. Nevertheless, knowledge is limited on the microbial community structures and functions of natural marine biofilms and their influence on global geochemical cycles. Microbial cues, including secondary metabolites and microbial structures, regulate interactions between microorganisms, with their environment and with other benthic organisms, which affects their community succession and metamorphosis. Furthermore, marine biofilms are key mediators of marine biofouling, which greatly affect marine industries. In this Review, we discuss marine biofilm dynamics, including their diversity, abundance and functions. We also highlight knowledge gaps, areas for future research and potential biotechnological applications of marine biofilms.

High fat diet disrupts diurnal interactions between small intestinal host innate immune factor REG3γ and gut microbiota resulting in metabolic dysfunction

BackgroundCircadian rhythms are ubiquitous in nature, driving many bodily processes and behaviors, including sleep‐wake cycles and feeding patterns over 24 hours. We and others revealed gut microbes and their functional outputs also exhibit diurnal rhythms that are responsive to how much, what, and when food is consumed. These microbial cues are integrated into host circadian networks, serving as key regulators of metabolism. High fat (HF) diet disrupts diurnal microbial oscillations, impacting diet‐induced obesity (DIO). Apart from feeding, host factors that drive microbial oscillations, specifically in the small intestine, are complex and remain poorly understood. We hypothesized that HF diet disrupts coordination of diurnal rhythms between host‐derived antimicrobial peptides, particularly the host C‐type lectin Regenerating islet‐derived 3 gamma(Reg3γ), and gut microbial community membership, contributing to DIO and metabolic dysfunction.ResultsDistal ileal tissue and luminal contents were collected every 4 hours over a 12:12 LD cycle from regular chow (RC) vs. HF‐fed germ‐free (GF) and conventionally raised (CONV) C57Bl/6 age and sex‐matched mice. Ileal tissue gene expression analysis reveals diurnal Reg3γ expression is only observed in RC‐fed, but not HF‐fed, CONV mice. Illumina MiSeq 16S rRNA gene amplicon sequencing of ileal luminal contents indicates that HF diet significantly shifts microbial community membership with a corresponding reduction in oscillations relative to RC. Specific Lactobacillaceae bacteria selected by RC oscillate and exhibit positive correlation with Reg3γ expression, while HF promotes expansion of Clostridiales bacteria that negatively correlate with Reg3γ. Using both in vitro intestinal organoid and in vivomonoassociation of GF mice, we identified that exposure to bacterial strains representative of those selected by RC or HF diet elicit a bi‐directional interaction with Reg3γ; only RC‐driven Lactobacillus rhamnosus GG (LGG) induces diurnal Reg3γ expression, suggesting a bacteria‐specific effect. While dietary composition remains the primary driver of microbial oscillators, host factors such as Reg3γ provide secondary cues to drive abundance and oscillation of key gut microbes that are essential for host metabolic homeostasis.ConclusionsTogether, these results demonstrate transkingdom co‐evolved biological rhythms that are primarily influenced by diet, and reciprocal sensor‐effector signals between host and microbial components. The diurnal dynamics of host innate immune factors and specific diet‐induced ileal gut microbes are key for the maintenance of regional intestinal host‐microbe interactions and metabolic homeostasis.

Biofluids in orofacial pain

Orofacial pain is a dental specialty that focuses on diagnosing and treating long-term, complicated facial discomfort caused by oromotor disorders. This pain is similar to pain elsewhere in the body and is generally caused by tissue damages. The pathogenesis of orofacialpain might be caused by orofacial structures illness, musculoskeletal system disorders, peripheral or central nervous system disorders, systemic diseases, psychological problems, or the result of inadequate sleep. One method to diagnose is evaluating the molecular and microbial cues of biological fluids, which may indicate the occurrence or progression of the disease. This article provides an overview of these biofluids and biomarkers and their role in progression of orofacial diseases.

Cell-intrinsic Aryl Hydrocarbon Receptor signalling is required for the resolution of injury-induced colonic stem cells

The aryl hydrocarbon receptor (AHR) is an environmental sensor that integrates microbial and dietary cues to influence physiological processes within the intestinal microenvironment, protecting against colitis and colitis-associated colorectal cancer development. Rapid tissue regeneration upon injury is important for the reinstatement of barrier integrity and its dysregulation promotes malignant transformation. Here we show that AHR is important for the termination of the regenerative response and the reacquisition of mature epithelial cell identity post injury in vivo and in organoid cultures in vitro. Using an integrative multi-omics approach in colon organoids, we show that AHR is required for timely termination of the regenerative response through direct regulation of transcription factors involved in epithelial cell differentiation as well as restriction of chromatin accessibility to regeneration-associated Yap/Tead transcriptional targets. Safeguarding a regulated regenerative response places AHR at a pivotal position in the delicate balance between controlled regeneration and malignant transformation.

P059 Diet controls segmented filamentous bacteria in driving Crohn’s disease-like inflammation in TNFdeltaARE mice

Abstract Background Crohn’s disease (CD)-like inflammation in TNFdeltaARE mice (ARE) mice is triggered by dysbiotic gut microbial communities. Similar to the therapeutic effect of exclusive enteral nutrition in CD, dietary intervention using semi-synthetic experimental diet prevents disease development in ARE mice. The aim of this study is to identify the causal microbial cues responsible for CD-like inflammation and to dissect the protective role of diet in ARE mice. Methods Bacterial communities in ARE and wildtype (WT) mice were profiled by 16S rRNA gene sequencing, FISH and qPCR. Germfree WT and ARE mice were colonized with segmented filamentous bacteria (SFB) from dysbiotic ARE mice. Disease activity, cytokine expression, mucosal immune cell infiltrates as well as Paneth and goblet cells phenotypes were assessed in murine ileal and colonic tissue. To assess the influence of diet on disease development, ARE mice were fed either chow, purified semi-synthetic experimental diet (SED) or fiber-rich diet. Impact of SFB on ileo-colonic inflammation was tested in additional mouse models (XIAP-/- and IL10 -/-). Mucosal biopsies from adult and pediatric IBD patients (N=407) were screened for the presence of human SFB using SFB-specific PCR primers. Results Under specific pathogen-free (SPF) conditions, ARE mice developed CD-like ileal inflammation which correlated strongly with increasing abundance of SFB. Mono-colonization of germfree ARE mice with SFB resulted in severe enterocolitis. Parallel to high tissue levels of TNF and IL-17, SPF-mediated inflammation was associated with neutrophil infiltration and the expansion of IFNγ expressing Th1 cells in the mucosa. Loss of Paneth and goblet cell function allowed SFB to penetrate mucus layers towards the epithelium. SED eradicated SFB and completely abolished inflammation in ARE mice. In contrast, fiber-rich diet partially restored SFB colonization and led to increased levels of inflammatory cytokines. SFB mono-colonization of GF XIAP-/- and IL10 -/- failed to induce inflammation, emphasizing host specificity to the mucosa-adherent SFB. Presence of SFB was confirmed in 12 ileal and 11 colonic mucosal biopsies from IBD patients with active or inactive disease. Conclusion We identified a novel pathogenic role of SFB in driving severe CD-like ileo-colonic inflammation characterized by loss of Paneth and goblet cell functions in ARE mice. Detection of SFB in mucosal biopsies of patients with IBD opens new perspectives about therapeutic strategies targeting SFB-mediated processes. Purified diet antagonized SFB colonization and prevented disease development in ARE mice in contrast to fiber-rich diet, clearly demonstrating the important role of diet in modulating a novel IBD-relevant pathobiont.

Intestinal Gpr17 deficiency improves glucose metabolism by promoting GLP-1 secretion.

SUMMARYG protein-coupled receptors (GPCRs) in intestinal enteroendocrine cells (EECs) respond to nutritional, neural, and microbial cues and modulate the release of gut hormones. Here we show that Gpr17, an orphan GPCR, is co-expressed in glucagon-like peptide-1 (GLP-1)-expressing EECs in human and rodent intestinal epithelium. Acute genetic ablation of Gpr17 in intestinal epithelium improves glucose tolerance and glucose-stimulated insulin secretion (GSIS). Importantly, inducible knockout (iKO) mice and Gpr17 null intestinal organoids respond to glucose or lipid ingestion with increased secretion of GLP-1, but not the other incretin glucose-dependent insulinotropic polypeptide (GIP). In an in vitro EEC model, overexpression or agonism of Gpr17 reduces voltage-gated calcium currents and decreases cyclic AMP (cAMP) production, and these are two critical factors regulating GLP-1 secretion. Together, our work shows that intestinal Gpr17 signaling functions as an inhibitory pathway for GLP-1 secretion in EECs, suggesting intestinal GPR17 is a potential target for diabetes and obesity intervention.

Toward Elucidating the Human Gut Microbiota-Brain Axis: Molecules, Biochemistry, and Implications for Health and Diseases.

In recent years, a substantial amount of data have supported an active role of gut microbiota in mediating mammalian brain function and health. Mining gut microbiota and their metabolites for neuroprotection is enticing but requires that the fundamental biochemical details underlying such microbiota-brain crosstalk be deciphered. While a neuronal gut-brain axis (through the vagus nerve) is not disputable, accumulating studies also point to a humoral route (via blood/lymphatic circulation) by which innumerable microbial molecular cues translocate from local gut epithelia to circulation with potentials to further cross the blood-brain barrier and reach the brain. In this Perspective, we review a realm of gut microbial molecules to evaluate their fate, function, and neuroactivities in vivo as mediated by microbiota. We turn to seminal studies of neurophysiology and neurologic disease models for the elucidation of biochemical pathways that link microbiota to gut-brain signaling. In addition, we discuss opportunities and challenges for advancing the microbiota-brain axis field while calling for high-throughput discovery of microbial molecules and studies for resolving the interspecies, interorgan, and interclass interaction among these neuroactive microbial molecules.

Gut Microbial Metabolite-Mediated Regulation of the Intestinal Barrier in the Pathogenesis of Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD) is a chronic inflammatory disease. The disease has a multifactorial aetiology, involving genetic, microbial as well as environmental factors. The disease pathogenesis operates at the host–microbe interface in the gut. The intestinal epithelium plays a central role in IBD disease pathogenesis. Apart from being a physical barrier, the epithelium acts as a node that integrates environmental, dietary, and microbial cues to calibrate host immune response and maintain homeostasis in the gut. IBD patients display microbial dysbiosis in the gut, combined with an increased barrier permeability that contributes to disease pathogenesis. Metabolites produced by microbes in the gut are dynamic indicators of diet, host, and microbial interplay in the gut. Microbial metabolites are actively absorbed or diffused across the intestinal lining to affect the host response in the intestine as well as at systemic sites via the engagement of cognate receptors. In this review, we summarize insights from metabolomics studies, uncovering the dynamic changes in gut metabolite profiles in IBD and their importance as potential diagnostic and prognostic biomarkers of disease. We focus on gut microbial metabolites as key regulators of the intestinal barrier and their role in the pathogenesis of IBD.

Bacterial marginolactones trigger formation of algal gloeocapsoids, protective aggregates on the verge of multicellularity

Photosynthetic microorganisms including the green alga Chlamydomonas reinhardtii are essential to terrestrial habitats as they start the carbon cycle by conversion of CO 2 to energy-rich organic carbohydrates. Terrestrial habitats are densely populated, and hence, microbial interactions mediated by natural products are inevitable. We previously discovered such an interaction between Streptomyces iranensis releasing the marginolactone azalomycin F in the presence of C. reinhardtii . Whether the alga senses and reacts to azalomycin F remained unknown. Here, we report that sublethal concentrations of azalomycin F trigger the formation of a protective multicellular structure by C. reinhardtii , which we named gloeocapsoid. Gloeocapsoids contain several cells which share multiple cell membranes and cell walls and are surrounded by a spacious matrix consisting of acidic polysaccharides. After azalomycin F removal, gloeocapsoid aggregates readily disassemble, and single cells are released. The presence of marginolactone biosynthesis gene clusters in numerous streptomycetes, their ubiquity in soil, and our observation that other marginolactones such as desertomycin A and monazomycin also trigger the formation of gloeocapsoids suggests a cross-kingdom competition with ecological relevance. Furthermore, gloeocapsoids allow for the survival of C. reinhardtii at alkaline pH and otherwise lethal concentrations of azalomycin F. Their structure and polysaccharide matrix may be ancestral to the complex mucilage formed by multicellular members of the Chlamydomonadales such as Eudorina and Volvox . Our finding suggests that multicellularity may have evolved to endure the presence of harmful competing bacteria. Additionally, it underlines the importance of natural products as microbial cues, which initiate interesting ecological scenarios of attack and counter defense.

Aryl Hydrocarbon Receptor Deficiency in Intestinal Epithelial Cells Aggravates Alcohol-Related Liver Disease.

Background & AimsThe ligand-activated transcription factor, aryl hydrocarbon receptor (AHR) can sense xenobiotics, dietary, microbial, and metabolic cues. Roles of Ahr in intestinal epithelial cells (IECs) have been much less elucidated compared with those in intestinal innate immune cells. Here, we explored whether the IEC intrinsic Ahr could modulate the development of alcohol-related liver disease (ALD) via the gut–liver axis.MethodsMice with IEC specific Ahr deficiency (AhrΔIEC) were generated and fed with a control or ethanol diet. Alterations of intestinal microbiota and metabolites were investigated by 16S ribosomal RNA sequencing, metagenomics, and untargeted metabolomics. AHR agonists were used to evaluate the therapeutic potentials of intestinal Ahr activation for ALD treatment.ResultsAhrΔIEC mice showed more severe liver injury after ethanol feeding than control mice. Ahr deficiency in IECs altered the intestinal metabolite composition, creating an environment that promoted the overgrowth of Helicobacter hepaticus and Helicobacter ganmani in the gut, enhancing their translocation to mesenteric lymph nodes and liver. Among the altered metabolites, isobutyric acid was increased in the cecum of ethanol-fed AhrΔIEC mice relative to control mice. Furthermore, both H.hepaticus and isobutyric acid administration aggravated ethanol-induced liver injury in vivo and in vitro. Supplementation with AHR agonists, 6-formylindolo[3,2-b]carbazole and indole-3-carbinol, protected mice from ALD development by specifically activating intestinal Ahr without affecting liver Ahr function. Alcoholic patients showed lower intestinal AHR expression and higher H.hepaticus levels compared with healthy individuals.ConclusionsOur results indicate that targeted restoration of IEC intrinsic Ahr function may present as a novel approach for ALD treatment.