Methanobrevibacter smithii

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Methanobrevibacter smithii
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Archaea
Kingdom: Euryarchaeota
Class: Methanobacteria
Order: Methanobacteriales
Family: Methanobacteriaceae
Genus: Methanobrevibacter
Species:
M. smithii
Binomial name
Methanobrevibacter smithii
Balch and Wolfe 1981

Methanobrevibacter smithii is the predominant archaeon in the microbiota of the human gut. M. smithii has a coccobacillus shape. It plays an important role in the efficient digestion of polysaccharides (complex sugars) by consuming the end products of bacterial fermentation. Methanobrevibacter smithii is a single-celled microorganism from the Archaea domain. M. smithii is a methanogen, and a hydrogenotroph that recycles the hydrogen by combining it with carbon dioxide to methane. The removal of hydrogen by M. smithii is thought to allow an increase in the extraction of energy from nutrients by shifting bacterial fermentation to more oxidized end products. [1]

Contents

Methanobrevibacter smithii is also found in dental plaque and in the vagina (with vaginosis). [2]

Importance in the human gut

The human gut microbiota consists of three main groups of hydrogen-consuming microorganisms or hydrogenotrophs: methanogens including M. smithii; various acetogenic bacteria; and sulfate-reducing bacteria. The different roles of these microorganisms are helpful in understanding how hydrogen metabolism affects the efficiency of dietary fermentation. [3] Accumulation of hydrogen in the gut reduces the efficiency of microbial fermentation as well as the yield of energy. Methanogenic archaea are therefore particularly significant for the human gut, because they are pivotal in the removal of excess hydrogen. [1] M. smithii is the most common methanogenic archaeon in the human gut microbiota. M. smithii is paramount in digestive processes, and has a high prevalence in human feces. [4]

The gut microbiota is dominated by gram-negative Bacteroidota, and Bacillota (mostly gram-positive). Archaea are most prominently represented by the methanogenic M. smithii. M. smithii is believed to be a therapeutic target for manipulation and an adaptation to the gut ecosystem. [5]

M. smithii has significant enrichment of genes involved in the utilization of carbon dioxide (CO2), hydrogen gas (H2), and formate (HCO2−) for methanogenesis. It also has an intact pathway to allow for CO2 utilization gene cluster for the methanogenic consumption of Bacteroides thetaiotaomicron -produced metabolite. [5]

M. smithii supports methanogenic and nonmethanogenic removal of diverse bacterial end products of fermentation. [5]

The dominant archaeon in the human gut ecosystem affects the specificity and efficiency of bacterial digestion of dietary polysaccharides. This influences the person’s calorie harvest and body fat. [5] M. smithii, along with certain bacteria, is more often found in lean individuals than in those who are overweight. [6] Researchers have sequenced M. smithii genome, indicating that M. smithii may be a therapeutic target for reducing energy harvest in obese humans. [5]

Cell wall and cell membrane compared to bacteria

The cell wall and cell membrane of Methanobrevibacter smithii determine susceptibility to antibiotics and statins. The cell wall is composed of pseudopeptidoglycan (and not peptidoglycan as in bacteria) which makes archaea resistant to lysozyme and many antibiotics that interfere with cell wall synthesis. The cell membrane consists of a lipid bilayer or monolayer, the backbone of which is composed of isoprene units that are linked to glycerol by ether bonds. In contrast, the lipid bilayer of bacteria consists of a fatty acid backbone that is linked to glycerol by an ester bond. The presence of statin-sensitive isoprene units in the cell membrane of archaea allows statins to selectively interfere with the growth of archaea while leaving the cell membrane of bacteria unaffected. While bacteria do not use isoprene units in their cell membrane they are still required elsewhere. These bacterial isoprene units are, however, synthesized by the mevalonate pathway (MEP) that is not inhibited by statins. [7]

In anorexic patients

In 2009, the largest human study concerning obesity and gut microbiota to date was conducted. Obesity disorders are the result of an imbalance and have serious consequences such as cardiovascular disease, type 2 diabetes, and colon cancer. The gut microbiota and environment contributes to the energy imbalance because of its involvement in energy intake, conversion and storage. Culture-independent methods have shown that high proportions of methanogens can comprise up to 10% of all anaerobes in the colons of healthy adults. The quantification average of M. smithii for the anorexic group was much greater than the lean and obese group. Thus, higher amounts of M. smithii were found in anorexic patients than lean patients.

The development of Methanobrevibacter in anorexia patients may be associated with an adaptive attempt towards optimal exploitation of the low caloric diet of anorexic patients. Hence, an increase in M. smithii leads to the optimization of food transformation in low caloric diets. M. smithii could also be related to constipation, a common condition for anorexic patients. [1]

M. smithii and constipation

Observational studies show a strong association between delayed intestinal transit and the production of methane. Experimental data suggest a direct inhibitory activity of methane on the colonic and ileal smooth muscle and a possible role for methane as a gasotransmitter. Statins can inhibit archaeal cell membrane biosynthesis apparently without affecting bacterial numbers as demonstrated in livestock and humans. This opens the possibility of a therapeutic intervention that targets a specific etiological factor of constipation while protecting the intestinal microbiome. While it is generally believed that statins inhibit methane production via their effect on cell membrane biosynthesis, mediated by inhibition of the HMG-CoA reductase, there is accumulating evidence for an alternative or additional mechanism of action where statins inhibit methanogenesis directly. It appears that this other mechanism may predominate when the lactone form of statins, particularly lovastatin, is administered. [7]

Related Research Articles

<span class="mw-page-title-main">Flatulence</span> Bodily function of expelling intestinal gas from the anus

Flatulence, in humans, is the expulsion of gas from the intestines via the anus, commonly referred to as farting, tooting, or passing gas. "Flatus" is the medical word for gas generated in the stomach or bowels. A proportion of intestinal gas may be swallowed environmental air, and hence flatus is not entirely generated in the stomach or bowels. The scientific study of this area of medicine is termed flatology.

Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and belong to the domain Archaea. All known methanogens are members of the archaeal phylum Euryarchaeota. Methanogens are common in wetlands, where they are responsible for marsh gas, and in the digestive tracts of animals such as ruminants and many humans, where they are responsible for the methane content of belching in ruminants and flatulence in humans. In marine sediments, the biological production of methane, also termed methanogenesis, is generally confined to where sulfates are depleted, below the top layers. Moreover, methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments. Others are extremophiles, found in environments such as hot springs and submarine hydrothermal vents as well as in the "solid" rock of Earth's crust, kilometers below the surface.

Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with anaerobic bacteria. The production of methane is an important and widespread form of microbial metabolism. In anoxic environments, it is the final step in the decomposition of biomass. Methanogenesis is responsible for significant amounts of natural gas accumulations, the remainder being thermogenic.

<span class="mw-page-title-main">Small intestinal bacterial overgrowth</span> Medical condition

Small intestinal bacterial overgrowth (SIBO), also termed bacterial overgrowth, or small bowel bacterial overgrowth syndrome (SBBOS), is a disorder of excessive bacterial growth in the small intestine. Unlike the colon, which is rich with bacteria, the small bowel usually has fewer than 100,000 organisms per millilitre. Patients with bacterial overgrowth typically develop symptoms which may include nausea, bloating, vomiting, diarrhea, malnutrition, weight loss and malabsorption, which is caused by a number of mechanisms.

Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.

In biology, syntrophy, synthrophy, or cross-feeding is the phenomenon of one species feeding on the metabolic products of another species to cope up with the energy limitations by electron transfer. In this type of biological interaction, metabolite transfer happens between two or more metabolically diverse microbial species that live in close proximity to each other. The growth of one partner depends on the nutrients, growth factors, or substrates provided by the other partner. Thus, syntrophism can be considered as an obligatory interdependency and a mutualistic metabolism between two different bacterial species.

<span class="mw-page-title-main">Methanobacteria</span> Class of archaea

Methanobacteria is a class of archaeans in the kingdom Euryarchaeota. Several of the classes of the Euryarchaeota are methanogens and the Methanobacteria are one of these classes.

Methanocaldococcus formerly known as Methanococcus is a genus of coccoid methanogen archaea. They are all mesophiles, except the thermophilic M. thermolithotrophicus and the hyperthermophilic M. jannaschii. The latter was discovered at the base of a “white smoker” chimney at 21°N on the East Pacific Rise and it was the first archaean genome to be completely sequenced, revealing many novel and eukaryote-like elements.

Methanobrevibacter is a genus of archaeans in the family Methanobacteriaceae. The species within Methanobrevibacter are strictly anaerobic archaea that produce methane, for the most part through the reduction of carbon dioxide via hydrogen. Most species live in the intestines of larger organisms, such as termites and are responsible for the large quantities of greenhouse gases that they produce. Mbr. smithii, found in the human intestine, may play a role in obesity.

In taxonomy, Methanosphaera is a genus of microbes within the family Methanobacteriaceae. It was distinguished from other genera within Methanobacteriaceae in 1985 on the basis of the oligonucleotide sequence of its 16S RNA. Like other archaea within Methanobacteriaceae, those of Methanosphaera are methanogens, but while most use formate to reduce carbon dioxide, those of Methanosphaera use hydrogen to reduce methanol to methane.

Archaeol is composed of two phytanyl chains linked to the sn-2 and sn-3 positions of glycerol. As its phosphate ester, it is a common component of the membranes of archaea.

Methanobrevibacter cuticularis is a species of methanogen archaeon. It was first isolated from the hindgut of the termite Reticulitermes flavipes. It is rod-shaped, ranging in size from 0.34 to 1.6 µm and possesses polar fibers. Its morphology, gram-positive staining reaction, resistance to cell lysis by chemical agents and narrow range of utilizable substrates are typical of species belonging to the family Methanobacteriaceae. It habitates on or near the hindgut epithelium and also attached to filamentous prokaryotes associated with the gut wall. It is one of the predominant gut biota.

Methanobrevibacter curvatus is a species of methanogen archaeon. It was first isolated from the hindgut of the termite Reticulitermes flavipes. It is rod-shaped, ranging in size from 0.34 to 1.6 µm and possesses polar fibers. Its morphology, gram-positive staining reaction, resistance to cell lysis by chemical agents and narrow range of utilisable substrates are typical of species belonging to the family Methanobacteriaceae. It habitates on or near the hindgut epithelium and also attached to filamentous prokaryotes associated with the gut wall. It is one of the predominant gut biota.

Methanobrevibacter filiformis is a species of methanogen archaeon. It was first isolated from the hindgut of the termite Reticulitermes flavipes. It is rod-shaped and possesses polar fibers. Its morphology, gram-positive staining reaction, resistance to cell lysis by chemical agents and narrow range of utilisable substrates are typical of species belonging to the family Methanobacteriaceae. It habitates on or near the hindgut epithelium and also attached to filamentous prokaryotes associated with the gut wall. It is one of the predominant gut biota.

Methanobrevibacter gottschalkii is a species of methanogen archaeon, named after Gerhard Gottschalk.

Methanobrevibacter thaueri is a species of methanogen archaeon, named after Rolf K. Thauer.

Methanobrevibacter woesei is a species of methanogen archaeon, named after Carl R. Woese.

Methanosphaera stadtmaniae is a methanogen archaeon. It is a non-motile, Gram-positive, spherical-shaped organism that obtains energy by using hydrogen to reduce methanol to methane. It does not possess cytochromes and is part of the large intestine's biota.

Hydrogenotrophs are organisms that are able to metabolize molecular hydrogen as a source of energy.

<span class="mw-page-title-main">Armophorea</span> Class of single-celled organisms

Armophorea is a class of ciliates in the subphylum Intramacronucleata. . It was first resolved in 2004 and comprises three orders: Metopida, Clevelandellida, and Armophorida. Previously members of this class were thought to be heterotrichs because of similarities in morphology, most notably a characteristic dense arrangement of cilia surrounding their oral structures. However, the development of genetic tools and subsequent incorporation of DNA sequence information has led to major revisions in the evolutionary relationships of many protists, including ciliates. Metopids, clevelandellids, and armophorids were grouped into this class based on similarities in their small subunit rRNA sequences, making them one of two so-called "riboclasses" of ciliates, however, recent analyses suggest that Armophorida may not be related to the other two orders.

References

  1. 1 2 3 Armougom F; Henry M; Vialettes B; Raccah D; et al. (2009). "Monitoring Bacterial Community of Human Gut Microbiota Reveals an Increase in Lactobacillus in Obese Patients and Methanogens in Anorexic Patients". PLOS ONE. 4 (9): e7125. Bibcode:2009PLoSO...4.7125A. doi: 10.1371/journal.pone.0007125 . PMC   2742902 . PMID   19774074.
  2. ↑ Belay, N; Mukhopadhyay, B; Conway de Macario, E; Galask, R; Daniels, L. 1990. Methanogenic bacteria in human vaginal samples. Journal of Clinical Microbiology, 28 (7), 1666–1668.
  3. ↑ Hansen, Elizabeth E.; Lozupone, Catherine A.; Rey, Federico E.; Wu, Meng; Guruge, Janaki L.; Narra, Aneesha; Goodfellow, Jonathan; Zaneveld, Jesse R.; McDonald, Daniel T. (2011-03-15). "Pan-genome of the dominant human gut-associated archaeon, Methanobrevibacter smithii, studied in twins". Proceedings of the National Academy of Sciences of the United States of America. 108 Suppl 1 (Suppl 1): 4599–4606. Bibcode:2011PNAS..108.4599H. doi: 10.1073/pnas.1000071108 . ISSN   1091-6490. PMC   3063581 . PMID   21317366.
  4. ↑ Bedis, D., Mireille, H. (2009). "High Prevalence of Methanobrevibacter smithii and Methanosphaera stadtmanae Detected in the Human Gut Using an Improved DNA Detection Protocol." PLOS One 4(9) e7063.
  5. 1 2 3 4 5 Buck, S., Hansen, E., (2007). "Genomic and metabolic adaptations of Methanobrevibacter smithii to the human gut." Proceedings of the National Academy of Sciences of the United States of America 104, 10643-10648.
  6. ↑ Stenman LK, Burcelin R, Lahtinen S (2016). "Establishing a causal link between gut microbes, body weight gain and glucose metabolism in humans - towards treatment with probiotics". Beneficial Microbes . 7 (1): 11–22. doi:10.3920/BM2015.0069. PMID   26565087.
  7. 1 2 Gottlieb, K., Wacher, V., Sliman, J., & Pimentel, M. (2015). Review article: inhibition of methanogenic archaea by statins as a targeted management strategy for constipation and related disorders. Alimentary Pharmacology & Therapeutics.

Further reading

Bang, Corinna; Weidenbach, Katrin; Gutsmann, Thomas; Heine, Holgar; Schmitz, Ruth A. (2014). "The Intestinal Archaea Methanosphaera stadtmanae and Methanobrevibacter smithii Activate Human Dendritic Cells". PLOS ONE. 9 (6): e99411. Bibcode:2014PLoSO...999411B. doi: 10.1371/journal.pone.0099411 . PMC   4051749 . PMID   24915454.

Kim, Gene; Deepinder, Fnu; Morales, Walter; Hwang, Laura; Weitsman, Stacy; Chang, Christopher; Gunsalus, Robert; Pimentel, Mark (December 2012). "Methanobrevibacter smithii Is the Predominant Methanogen in Patients with Constipation-Predominant IBS and Methane on Breath". Digestive Diseases and Sciences. 57 (12): 3213–3218. doi:10.1007/s10620-012-2197-1. PMID   22573345. S2CID   207113756.

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