It’s not often that I get to write about the more esoteric members of our gut biomes. Our bacteria get the most hype in the scientific literature, but as you all know, there are many other kinds of residents of our inner ecosystems. I was excited, therefore, to spot an article late last week about Archaea.[i]
Let me start with a definition: “Archaea [which is pronounced ar-key-a] are organisms whose cells lack a defined nucleus. They are not bacteria (their cell walls are different) and they are not eukaryotes (which are complex, multi-celled organisms, including plants and animals, whose cells do have a defined nucleus). Many are found in anaerobic (without air) environments, including hot springs, marshes and the guts of animals and humans.[ii]
A study just published in the Journal of Allergy and Clinical Immunology[iii] looked at the relationship of gut Archaea to the development of childhood asthma. The researchers found that high levels of a species, Methanosphaera stadtmanae, were associated with a lower risk for asthma. They analyzed 472 samples in total, and concluded that, “…the presence of M. stadtmanae was associated with a lower risk for asthma at 6 to 10 years of age.” Higher levels of this organism are also somewhat associated with a lower risk for eczema, airborne allergies and food allergy, but not to the point of reaching statistical significance. They have not, as yet, figured out the mechanism of action, but believe their results were meaningful enough to indicate that a beneficial link very likely exists.
I myself know very little about Archaea, so thought I’d do some snooping around to see what other kinds of information I could glean to share with you. I did find some interesting papers. For example, just this past February, a paper was published looking at Archaea’s involvement in the development of abscesses. An interesting couple of sentences from the abstract: “They have been implicated in dysbiosis of the oral microbiota…They have also been associated with dysbiosis of the digestive tract microbiota linked to metabolic disorders (anorexia, malnutrition and obesity) and with lesions of the digestive tract (colon cancer).”[iv]
Perhaps the most interesting thing I found was a paper from last year which took an in-depth look at what we currently know about Archaea’s involvement in human health and disease.[v] They state that the role these organisms play has been vastly underrated: “It has been reported that the impact of methanogens [methane producing Archaea] of the gut microbiota on pathological conditions has been grossly underestimated. Methanobrevibacter smithii and Methanosphaera stadtmanae are specifically recognized by the human innate immune system, and it is considered that these species contribute to immune responses in the body, including inflammatory responses.” These organisms are found in the gut, on the skin, in the vagina, and in the mouth, including in dental plaque (with one species, Methanobrevibacter oralis, being significantly associated with periodontal disease). Whether or not though most are beneficial or pathogenic is currently unknown, but it seems likely that, like bacteria, helminths, etc, some species are good, some are bad, and perhaps, some can be both depending on circumstances.
An example of this (i.e. a species being beneficial or pathogenic, depending on circumstance): higher levels of certain Archaea are found in obese people. It is believed the organisms may improve the efficiency of energy (calorie) absorption from food. However, in those with anorexia, higher levels of the species, M. smithii, have been found, which would “lead to increased energy efficiency in severely low caloric diets.” The increased levels of the species may be the result of the body’s attempt to survive in the face of starvation.
There does seem to be a link between some Archaea and inflammatory bowel disease because they do seem to evoke an inflammatory response. That said, a 2012 study showed lower levels of Archaea in those with IBD as opposed to healthy individuals but there is some belief this is because diarrhea would lead to a reduction in numbers. No one is yet sure though.
There may also be associations between Archaea and irritable bowel syndrome, diverticulitis and periodontal disease. Their conclusion, “Several studies in the last decade directly or indirectly suggested a link between methanogens and a number of metabolic diseases. In addition…methanogens should be considered as an important target for the studies relating to modulation of the gut microbiota in humans for improving health or reducing risk of disease. Consequently, there is merit in proposing dietary intervention studies targeting the manipulation of archaeal components of the gut microbiome…This concept could even be extended to consider their use as a probiotic whereby live preparations of archaea could be used as dietary supplements (archaeobiotic).”
I reckon we are a long way from being able to buy Archaea probiotics. On the other hand, at least we know scientists are starting to take a meaningful look at these organisms which undoubtedly play a huge role in our biomes and thus, in our health. I will of course keep a close eye on developments!
[iii] Barnett D, Mommers M, Penders J, Arts ICW, Thijs C. Intestinal archaea inversely associated with childhood asthma [published online February 20, 2019]. J Allergy Clin Immunol. doi:10.1016/j.jaci.2019.02.009
[iv] Sogodogo, E, Drancourt, M, Grine, G. Methanogens as emerging pathogens in anaerobic abscesses. European Journal of Clinical Microbiology and Infectious Diseases. 2019. doi: 10.1007/s10096-019-03510-5
[v] Chaudhary, PP, Conway, PL, Schlundt, J. Methanogens in humans: potentially beneficial or harmful for health. Applied Microbiology and Biotechnology. 2018. DOI: