Akkermansia muciniphila is a well-studied anaerobic bacterium specialized in mucus degradation and associated with human health. Because of the structural resemblance of mucus glycans and free human ...milk oligosaccharides (HMOs), we studied the ability of A. muciniphila to utilize human milk oligosaccharides. We found that A. muciniphila was able to grow on human milk and degrade HMOs. Analyses of the proteome of A. muciniphila indicated that key-glycan degrading enzymes were expressed when the bacterium was grown on human milk. Our results display the functionality of the key-glycan degrading enzymes (α-L-fucosidases, β-galactosidases, exo-α-sialidases and β-acetylhexosaminidases) to degrade the HMO-structures 2'-FL, LNT, lactose, and LNT2. The hydrolysation of the host-derived glycan structures allows A. muciniphila to promote syntrophy with other beneficial bacteria, contributing in that way to a microbial ecological network in the gut. Thus, the capacity of A. muciniphila to utilize human milk will enable its survival in the early life intestine and colonization of the mucosal layer in early life, warranting later life mucosal and metabolic health.
The discovery of Akkermansia muciniphila has opened new avenues for the use of this abundant intestinal symbiont in next generation therapeutic products, as well as targeting microbiota dynamics. ...A. muciniphila is known to colonize the mucosal layer of the human intestine where it triggers both host metabolic and immune responses. A. muciniphila is particularly effective in increasing mucus thickness and increasing gut barrier function. As a result host metabolic markers ameliorate. The mechanism of host regulation is thought to involve the outer membrane composition, including the type IV pili of A. muciniphila, that directly signal to host immune receptors. At the same time the metabolic activity of A. muciniphila leads to the production of short chain fatty acids that are beneficial to the host and microbiota members. This contributes to host-microbiota and microbe-microbe syntrophy The mucolytic activity and metabolite production make A. muciniphila a key species in the mucus layer, stimulating beneficial mucosal microbial networks.
This well studied member of the microbiota has been studied in three aspects that will be further described in this review: i) A. muciniphila characteristics and mucin adaptation, ii) its role as key species in the mucosal microbiome, and iii) its role in host health.
Gut barrier function is key in maintaining a balanced response between the host and its microbiome. The microbiota can modulate changes in gut barrier as well as metabolic and inflammatory responses. ...This highly complex system involves numerous microbiota-derived factors. The gut symbiont Akkermansia muciniphila is positively correlated with a lean phenotype, reduced body weight gain, amelioration of metabolic responses and restoration of gut barrier function by modulation of mucus layer thickness. However, the molecular mechanisms behind its metabolic and immunological regulatory properties are unexplored. Herein, we identify a highly abundant outer membrane pili-like protein of A. muciniphila MucT that is directly involved in immune regulation and enhancement of trans-epithelial resistance. The purified Amuc_1100 protein and enrichments containing all its associated proteins induced production of specific cytokines through activation of Toll-like receptor (TLR) 2 and TLR4. This mainly leads to high levels of IL-10 similar to those induced by the other beneficial immune suppressive microorganisms such as Faecalibacterium prausnitzii A2-165 and Lactobacillus plantarum WCFS1. Together these results indicate that outer membrane protein composition and particularly the newly identified highly abundant pili-like protein Amuc_1100 of A. muciniphila are involved in host immunological homeostasis at the gut mucosa, and improvement of gut barrier function.
Obesity and type 2 diabetes are associated with low-grade inflammation and specific changes in gut microbiota composition. We previously demonstrated that administration of Akkermansia muciniphila to ...mice prevents the development of obesity and associated complications. However, the underlying mechanisms of this protective effect remain unclear. Moreover, the sensitivity of A. muciniphila to oxygen and the presence of animal-derived compounds in its growth medium currently limit the development of translational approaches for human medicine. We have addressed these issues here by showing that A. muciniphila retains its efficacy when grown on a synthetic medium compatible with human administration. Unexpectedly, we discovered that pasteurization of A. muciniphila enhanced its capacity to reduce fat mass development, insulin resistance and dyslipidemia in mice. These improvements were notably associated with a modulation of the host urinary metabolomics profile and intestinal energy absorption. We demonstrated that Amuc_1100, a specific protein isolated from the outer membrane of A. muciniphila, interacts with Toll-like receptor 2, is stable at temperatures used for pasteurization, improves the gut barrier and partly recapitulates the beneficial effects of the bacterium. Finally, we showed that administration of live or pasteurized A. muciniphila grown on the synthetic medium is safe in humans. These findings provide support for the use of different preparations of A. muciniphila as therapeutic options to target human obesity and associated disorders.
Akkermansia muciniphila
has evolved to specialize in the degradation and utilization of host mucus, which it may use as the sole source of carbon and nitrogen. Mucus degradation and fermentation by
...A. muciniphila
are known to result in the liberation of oligosaccharides and subsequent production of acetate, which becomes directly available to microorganisms in the vicinity of the intestinal mucosa. Coculturing experiments of
A
.
muciniphila
with non-mucus-degrading butyrate-producing bacteria
Anaerostipes caccae
,
Eubacterium hallii
, and
Faecalibacterium prausnitzii
resulted in syntrophic growth and production of butyrate. In addition, we demonstrate that the production of pseudovitamin B
12
by
E. hallii
results in production of propionate by
A. muciniphila
, which suggests that this syntrophy is indeed bidirectional. These data are proof of concept for syntrophic and other symbiotic microbe-microbe interactions at the intestinal mucosal interface. The observed metabolic interactions between
A
.
muciniphila
and butyrogenic bacterial taxa support the existence of colonic vitamin and butyrate production pathways that are dependent on host glycan production and independent of dietary carbohydrates. We infer that the intestinal symbiont
A. muciniphila
can indirectly stimulate intestinal butyrate levels in the vicinity of the intestinal epithelial cells with potential health benefits to the host.
The intestinal microbiota is said to be a stable ecosystem where many networks between microorganisms are formed. Here we present a proof of principle study of microbial interaction at the intestinal mucus layer. We show that indigestible oligosaccharide chains within mucus become available for a broad range of intestinal microbes after degradation and liberation of sugars by the species
Akkermansia muciniphila
. This leads to the microbial synthesis of vitamin B
12
, 1,2-propanediol, propionate, and butyrate, which are beneficial to the microbial ecosystem and host epithelial cells.
Host glycans are paramount in regulating the symbiotic relationship between humans and their gut bacteria. The constant flux of host-secreted mucin at the mucosal layer creates a steady niche for ...bacterial colonization. Mucin degradation by keystone species subsequently shapes the microbial community. This study investigated the transcriptional response during mucin-driven trophic interaction between the specialised mucin-degrader
Akkermansia muciniphila
and a butyrogenic gut commensal
Anaerostipes caccae
.
A. muciniphila
monocultures and co-cultures with non-mucolytic
A. caccae
from the
Lachnospiraceae
family were grown anaerobically in minimal media supplemented with mucin. We analysed for growth, metabolites (HPLC analysis), microbial composition (quantitative reverse transcription PCR), and transcriptional response (RNA-seq). Mucin degradation by
A. muciniphila
supported the growth of
A. caccae
and concomitant butyrate production predominantly via the acetyl-CoA pathway. Differential expression analysis (DESeq 2) showed the presence of
A. caccae
induced changes in the
A. muciniphila
transcriptional response with increased expression of mucin degradation genes and reduced expression of ribosomal genes. Two putative operons that encode for uncharacterised proteins and an efflux system, and several two-component systems were also differentially regulated. This indicated
A. muciniphila
changed its transcriptional regulation in response to
A. caccae
. This study provides insight to understand the mucin-driven microbial ecology using metatranscriptomics. Our findings show that the expression of mucolytic enzymes by
A. muciniphila
increases upon the presence of a community member. This could indicate its role as a keystone species that supports the microbial community in the mucosal environment by increasing the availability of mucin sugars.
The human gastrointestinal tract is colonized by a diverse microbial community, which plays a crucial role in human health. In the gut, a protective mucus layer that consists of glycan structures ...separates the bacteria from the host epithelial cells. These host-derived glycans are utilized by bacteria that have adapted to this specific compound in the gastrointestinal tract. Our study investigated the close interaction between two distinct gut microbiota members known to use mucus glycans, the generalist
Bacteroides thetaiotaomicron
and the specialist
Akkermansia muciniphila in vitro
and
in vivo
. The
in vitro
study, in which mucin was the only nutrient source, indicated that
B. thetaiotaomicron
significantly upregulated genes coding for Glycoside Hydrolases (GHs) and mucin degradation activity when cultured in the presence of
A. muciniphila
. Furthermore,
B. thetaiotaomicron
significantly upregulated the expression of a gene encoding for membrane attack complex/perforin (MACPF) domain in co-culture. The transcriptome analysis also indicated that
A. muciniphila
was less affected by the environmental changes and was able to sustain its abundance in the presence of
B. thetaiotaomicron
while increasing the expression of LPS core biosynthesis activity encoding genes (
O-
antigen ligase, Lipid A and Glycosyl transferases) as well as ABC transporters. Using germ-free mice colonized with
B. thetaiotaomicron
and/or
A. muciniphila
, we observed a more general glycan degrading profile in
B
.
thetaiotaomicron
while the expression profile of
A. muciniphila
was not significantly affected when colonizing together, indicating that two different nutritional niches were established in mice gut. Thus, our results indicate that a mucin degrading generalist adapts to its changing environment, depending on available carbohydrates while a mucin degrading specialist adapts by coping with competing microorganism through upregulation of defense related genes.
Summary
The growing commercial interest in multi‐strain formulations marketed as probiotics has not been accompanied by an equal increase in the evaluation of quality levels of these biotechnological ...products. The multi‐strain product VSL#3 was used as a model to setup a microbiological characterization that could be extended to other formulations with high complexity. Shotgun metagenomics by deep Illumina sequencing was applied to DNA isolated from the commercial VSL#3 product to confirm strains identity safety and composition. Single‐cell analysis was used to evaluate the cell viability, and β‐galactosidase and urease activity have been used as marker to monitor the reproducibility of the production process. Similarly, these lots were characterized in detail by a metaproteomics approach for which a robust protein extraction protocol was combined with advanced mass spectrometry. The results identified over 1600 protein groups belonging to all strains present in the VSL#3 formulation. Of interest, only 3.2 % proteins showed significant differences mainly related to small variations in strain abundance. The protocols developed in this study addressed several quality criteria that are relevant for marketed multi‐strain products and these represent the first efforts to define the quality of complex probiotic formulations such as VSL#3.
There are presently no accepted guidelines to control the microbiological quality of the commercialized probiotic products in spite of the demand for these. Without attempting to set new standards, we here evaluated the potential of high‐throughput and omics‐based approaches to contribute to the required quality control of probiotic products.
Knowledge of the functional roles and interspecies interactions are crucial for improving our understanding of the human intestinal microbiome in health and disease. However, the complexity of the ...human intestinal microbiome and technical challenges in investigating it pose major challenges. In this proof-of-concept study, we rationally designed, assembled and experimentally tested a synthetic Diet-based Minimal Microbiome (Db-MM) consisting of ten core intestinal bacterial species that together are capable of efficiently converting dietary fibres into short chain fatty acids (SCFAs). Despite their genomic potential for metabolic competition, all ten bacteria coexisted during growth on a mixture of dietary fibres, including pectin, inulin, xylan, cellobiose and starch. By integrated analyses of metabolite production, community composition and metatranscriptomics-based gene expression data, we identified interspecies metabolic interactions leading to production of key SCFAs such as butyrate and propionate. While public goods, such as sugars liberated from colonic fibres, are harvested by non-degraders, some species thrive by cross-feeding on energetically challenging substrates, including the butyrogenic conversion of acetate and lactate. Using a reductionist approach in an in-vitro system combined with functional measurements, our study provides key insights into the complex interspecies metabolic interactions between core intestinal bacterial species.
Akkermansia muciniphila is a member of the human gut microbiota where it resides in the mucus layer and uses mucin as the sole carbon, nitrogen and energy source. A. muciniphila is the only ...representative of the Verrucomicrobia phylum in the human gut. However, A. muciniphila 16S rRNA gene sequences have also been found in the intestines of many vertebrates.
We detected A. muciniphila-like bacteria in the intestines of animals belonging to 15 out of 16 mammalian orders. In addition, other species belonging to the Verrucomicrobia phylum were detected in fecal samples. We isolated 10 new A. muciniphila strains from the feces of chimpanzee, siamang, mouse, pig, reindeer, horse and elephant. The physiology and genome of these strains were highly similar in comparison to the type strain A. muciniphila Muc
. Overall, the genomes of the new strains showed high average nucleotide identity (93.9 to 99.7%). In these genomes, we detected considerable conservation of at least 75 of the 78 mucin degradation genes that were previously detected in the genome of the type strain Muc
.
The low genomic divergence observed in the new strains may indicate that A. muciniphila favors mucosal colonization independent of the differences in hosts. In addition, the conserved mucus degradation capability points towards a similar beneficial role of the new strains in regulating host metabolic health.
PDF
