Archaea, Bacteria / Humans

[Genady]

While there are so many detrimental bacteria, there are no detrimental archaea. Is it so? Why? 

[Arthur Smith]

12 minutes ago, Genady said:

While there are so many detrimental bacteria, there are no detrimental archaea. Is it so? Why? 

That's an intriguing question. I can see there is a pile of stuff with the consensus that while some archaea can be find in our gut, there is no unequivocal case of an archaean pathogen. Though I see some have alleged they may play a rôle in some diseases, the list includes Crohn's disease, arthritis, lupus and gingivitis. Certainly seems that Archaea are for the most part benign organisms. I have no immediate suggestion as to why. Will read some of the articles I've turned up.

[StringJunky]

Here's a compact discussion: https://microbiologysociety.org/blog/why-dont-archaea-cause-disease.html

[Arthur Smith]

5 minutes ago, StringJunky said:

Here's a compact discussion: https://microbiologysociety.org/blog/why-dont-archaea-cause-disease.html

Thanks,that's helpful. Suggests that archaea are being overlooked less than previously. From an evolutionary point of view, an organism with no volition (caveat on motile bacteria and Archaea) can't help but profit from an opportunity presented. Whilst Archaea are an ancient kingdom,  they have stumbled (or the motile ones tumbled) upon recent opportunities such as the gut of humans.

A recent study on Koreans. I'm frankly staggered at the abundance and variety. Opportunity for symbiont, parasite and pathogen.

 

[Genady]

Let's ask it differently: of all the known prokaryotic pathogens, what percent are archaea? 

[Genady]

3 hours ago, StringJunky said:

Here's a compact discussion: https://microbiologysociety.org/blog/why-dont-archaea-cause-disease.html

They found some evidence of an association between some disease and archaea, but no evidence of archaea causing a disease, yet.

Maybe it is fortunate, because it might be difficult to develop an antibiotic targeting archaea due to their biochemistry being more similar to ours than that of bacteria. 

[StringJunky]

5 minutes ago, Genady said:

They found some evidence of an association between some disease and archaea, but no evidence of archaea causing a disease, yet.

Maybe it is fortunate, because it might be difficult to develop an antibiotic targeting archaea due to their biochemistry being more similar to ours than that of bacteria. 

The awareness of Archaea as a distinct group appears to be quite young.... 45 years.  From the link:

Quote

Leeuwenhoek first described bacteria in 1674, archaea were only recognised as a separate group of prokaryotes by Carl Woese in 1977.

 

Edited January 22, 2022 by StringJunky

[Genady]

15 minutes ago, StringJunky said:

The awareness of Archaea as a distinct group appears to be quite young.... 45 years.  From the link:

 

I'm not sure it is technically correct to say that Leeuwenhoek first described bacteria in 1674. We didn't know of archaea as a separate domain until 1977, but it was there, mixed up with bacteria. Leeuwenhoek first described prokaryotes in 1674, he certainly couldn't distinguish between bacteria and archaea. Also, prokaryotic pathogens were found for long time, before 1977. Now, we can separate them into bacteria pathogens and archaea pathogens. The result of this separation: all of them turned out to be bacteria, no archaea.

[StringJunky]

41 minutes ago, Genady said:

I'm not sure it is technically correct to say that Leeuwenhoek first described bacteria in 1674. We didn't know of archaea as a separate domain until 1977, but it was there, mixed up with bacteria. Leeuwenhoek first described prokaryotes in 1674, he certainly couldn't distinguish between bacteria and archaea. Also, prokaryotic pathogens were found for long time, before 1977. Now, we can separate them into bacteria pathogens and archaea pathogens. The result of this separation: all of them turned out to be bacteria, no archaea.

My take on that article is that knowledge of Archaea has still much to be learned, and your conclusion is somewhat premature.

Quote

The evidence is growing that archaea may indulge in opportunistic pathogenesis: Methanobrevibacter smithii, apparently the most abundant methanogen in human guts, has been reported to be found more often in stool samples from patients with diverticulosis than healthy individuals. The non-acetoclastic M. smithii has also been reported to increase obesity in germ-free mouse models when grown syntrophically with Bacteroides thetaiotaomicron. Methanobrevibacter oralis is found in and around the gums of about 5% of healthy subjects but up to 10 times more frequently in patients exhibiting periodontitis symptoms.

Recently, this same organism was found in 40% of human brain abscesses but only 10% of controls. Injection of a million M. oralis cells into the brains of 22 mice resulted in 77% mortality after seven days, compared to no deaths in the 14 buffer-injected controls. Of course, the injection of a million live cells of almost any microbial species into a mouse’s brain seems likely to cause problems, but methanogens appear to be no different. While these studies have been relatively small scale and none of them have the 100% statistics we would like to satisfy Koch’s postulates, bacteria are often in the same position.

Meningitis can be caused by both viruses and bacteria – even bacterial meningitis is caused by different organisms. In the USA, bacterial meningitis cases can generally be attributed as about 45% Haemophilus influenzae, and roughly 16% each Neisseria meningitidis and Streptococcus pneumoniae (with proportions of the latter two species varying by season). This leaves nearly 20% of cases that could be caused by different organisms. No one questions that any of these organisms are pathogenic.

Why has it been so difficult to convincingly demonstrate archaeal pathogenesis? Our ability to detect archaea has certainly been an obstacle.

 

Edited January 22, 2022 by StringJunky

[Genady]

1 hour ago, StringJunky said:

My take on that article is that knowledge of Archaea has still much to be learned, and your conclusion is somewhat premature.

 

Quite possible.

Anyway, the findings like "has been reported to be found more often in stool samples from patients with diverticulosis than healthy individuals" are what I referred as association in the post above. Maybe archaea just prefer diseased tissues and thus are found more often in the patients with disease?

[StringJunky]

30 minutes ago, Genady said:

Quite possible.

Anyway, the findings like "has been reported to be found more often in stool samples from patients with diverticulosis than healthy individuals" are what I referred as association in the post above. Maybe archaea just prefer diseased tissues and thus are found more often in the patients with disease?

Yes, it does mention opportunism, of which that could be an opportunity. That might suggest they are not particularly virulent or pathogenic when immune defences are good.

Edited January 23, 2022 by StringJunky

[CharonY]

A couple of things: many archaea are difficult to cultivate and therefore presence and diversity of archaea were underestimated  for a long time. Cultivation-independent has remedied that somewhat (but only ramped up fairly recently), but without an accessible pure culture it is not easy to study their physiology and pathobiology. There is some evidence that in certain anaerobic dental infections and abcesses archaea are present, but without a good model system it would be hard to figure out whether they caused it, or were just opportunistic.

There is at least study where folks tried to infect mouse models with  methanogens, resulting in higher mortality compared to controls, but there is not a huge body of evidence  out yet. Moreover many of these studies are fairly new (a couple of years, really) and more studies and a better understanding of the role of archaea in our microbiome is needed.