3 ms·

> I STRONGLY believe there is a substantial central nervous system microbiome, but (spoiler alert) no evidence found in that search :) What gave you reason to

by lovich 2y ago

> I STRONGLY believe there is a substantial central nervous system microbiome, but (spoiler alert) no evidence found in that search :) What gave you reason to believe this if you found no evidence of it in your own search?

attemptone 2y ago
This might be too nitpicky, but isn't believe exactly what one has in absence of evidence?
- SamBam 2y ago
  They're is no evidence that Russell's Teapot is floating out in space in orbit around the sun, AND I don't believe that it's there. If I said "I STRONGLY believe that a teapot is out there," it would be reasonable to ask me why.
  - pessimizer 2y ago
    Also (and this is a pet peeve of mine), we're talking about evidence not proof. They're not the same thing. Just because there's evidence that something happened, it doesn't mean that it happened. Evidence is a thing that you claim could be part of an valid argument that something happened ("is consistent with"). This isn't a universal definition, but there's got to be some separation between proof and evidence. When there's evidence admitted into a court case, it doesn't necessarily mean that someone is guilty. When there's a lot of evidence and still no proof, you can and should (and will) still make a probabilistic case that something did happen. So I'd agree with and disagree with you. There's no evidence (that you know of) that Russell's Teapot is there, which is why you do not believe it is there. If somebody does believe it is there, but admits that they have no proof that it is there, it would be reasonable to ask what evidence makes them believe that it is there. Where I obviously agree with is that "belief" can't mean just something you want to think for no particular reason. Or if it does, it's certainly not worth talking about.
vlovich123 2y ago
Absence of proof is not proof of absence. I would imagine that it would take a lot of negative searches by many people trying different approaches to rule it out. The searches are likely to be carried out by people who believe in the idea rather than those that are skeptical they will find something (the skeptics will work on reproducing any positive results).
- tsimionescu 2y ago
  It should be noted that absence of proof is evidence for absence. And since in the physical sciences, unlike mathematics, actual proof of absence is impossible, absence of evidence (after thorough searches) is the best we've got to form a belief for absence of the phenomenon. That is, we believe, very strongly, that it's impossible for two masses to repel each other gravitationally, for example, but we will never have actual proof it's impossible. None of this to say that it's irrational to believe in a brain microbiome despite this search seeming fruitless, as there are good a priori arguments for expecting one to exist.
  - KineticLensman 2y ago
    > It should be noted that absence of proof is evidence for absence. Exactly. Like the apocryphal small chocolate teapot orbiting the Earth
    - pvaldes 2y ago
      But evidence of absence is, and in this case we have a lot. For the last 400 years, pathologists on every country had filleted and put, lets say tens thousands of human brains and human guts under the microscope. One of them has systematically a microbiome, easy to see. The other don't, except when is diseased or rotten. The sample token here is huge, maybe millions. If we would had searched 400 years for this chocolate teapot without finding it, we could conclude with a solid suspicion that there is not such thing. This is very different than just saying "I don't think that there is bacteria in the brain but I never searched for it". All pathology science is based in searching for it. We created gram staining dyes, scanners, tags, gold coated plates for electronic microscopes, DNA analysis... exactly for that. If there really is a microbiome living in each healthy brain, we should have found it 150 years ago.
j6m8 2y ago
Microbes are CRAZY. They're everywhere. Thermal vent-friendly microbes. Space-friendly microbes. Vacuum-resilient, heat-resilient, acid-resilient. Microbe-free-environment-friendly microbes [1]. It seems hard to imagine that a blood-brain barrier could really keep the brain sterile. We're lucky to live in a scientific era during which a "gut microbiome" is taken for granted (heck, even FDA-approved treatments depend on it! Google FMT, but don't click "images" from your work laptop), but it wasn't so long ago that we felt microbes were unlikely to live endogenously and harmlessly anywhere in the body. There were also some hypotheses (untested, if memory serves) that COVID-19 influenced olfactory neurons through direct infection. Don't tell the blood-brain barrier, but if I were a bacterium, the nasal palate would be my ingress strategy. Or maybe the gums or gut — one of the cranial nerves, certainly. [edit] I should clarify — covid is viral, not bacterial, but it does show that this is a potential entry vector. The central nervous system is incredibly complicated, and our symbiotic relationship with microbes is extraordinary. I think it does a disservice to bacteria to suppose they DON'T get involved in an organ :) [1] https://www.space.com/ryugu-asteroid-sample-earth-life-colonization https://www.space.com/ryugu-asteroid-sample-earth-life-colon...
- pazimzadeh 2y ago
  Our defenses are also crazy. For example, the inner mucus layer of the colon is able to keep trillions of bacteria at bay the vast majority of the time (unless there is inflammation or takeover by specific mucus-eating bacteria). Many of the proteins in the secreted mucus layers are still unknown in function, like FCGBP which comprises up to 40% of the protein content of mucus. The inner of the two Muc2 mucin-dependent mucus layers in colon is devoid of bacteria https://pubmed.ncbi.nlm.nih.gov/18806221/ https://pubmed.ncbi.nlm.nih.gov/18806221/ Bacteria penetrate the normally impenetrable inner colon mucus layer in both murine colitis models and patients with ulcerative colitis https://gut.bmj.com/content/63/2/281 https://gut.bmj.com/content/63/2/281 So I think without trillions of bacteria to exclude, in the absence of any other issues excluding bacteria from the brain seems pretty doable. Many viruses infect neurons, but they are way smaller than bacteria.

by lovich 2y ago

attemptone 2y ago

This might be too nitpicky, but isn't believe exactly what one has in absence of evidence?

SamBam 2y ago
They're is no evidence that Russell's Teapot is floating out in space in orbit around the sun, AND I don't believe that it's there. If I said "I STRONGLY believe that a teapot is out there," it would be reasonable to ask me why.
- pessimizer 2y ago
  Also (and this is a pet peeve of mine), we're talking about evidence not proof. They're not the same thing. Just because there's evidence that something happened, it doesn't mean that it happened. Evidence is a thing that you claim could be part of an valid argument that something happened ("is consistent with"). This isn't a universal definition, but there's got to be some separation between proof and evidence. When there's evidence admitted into a court case, it doesn't necessarily mean that someone is guilty. When there's a lot of evidence and still no proof, you can and should (and will) still make a probabilistic case that something did happen. So I'd agree with and disagree with you. There's no evidence (that you know of) that Russell's Teapot is there, which is why you do not believe it is there. If somebody does believe it is there, but admits that they have no proof that it is there, it would be reasonable to ask what evidence makes them believe that it is there. Where I obviously agree with is that "belief" can't mean just something you want to think for no particular reason. Or if it does, it's certainly not worth talking about.

vlovich123 2y ago

Absence of proof is not proof of absence. I would imagine that it would take a lot of negative searches by many people trying different approaches to rule it out. The searches are likely to be carried out by people who believe in the idea rather than those that are skeptical they will find something (the skeptics will work on reproducing any positive results).

tsimionescu 2y ago
It should be noted that absence of proof is evidence for absence. And since in the physical sciences, unlike mathematics, actual proof of absence is impossible, absence of evidence (after thorough searches) is the best we've got to form a belief for absence of the phenomenon. That is, we believe, very strongly, that it's impossible for two masses to repel each other gravitationally, for example, but we will never have actual proof it's impossible. None of this to say that it's irrational to believe in a brain microbiome despite this search seeming fruitless, as there are good a priori arguments for expecting one to exist.
- KineticLensman 2y ago
  > It should be noted that absence of proof is evidence for absence. Exactly. Like the apocryphal small chocolate teapot orbiting the Earth
  - pvaldes 2y ago
    But evidence of absence is, and in this case we have a lot. For the last 400 years, pathologists on every country had filleted and put, lets say tens thousands of human brains and human guts under the microscope. One of them has systematically a microbiome, easy to see. The other don't, except when is diseased or rotten. The sample token here is huge, maybe millions. If we would had searched 400 years for this chocolate teapot without finding it, we could conclude with a solid suspicion that there is not such thing. This is very different than just saying "I don't think that there is bacteria in the brain but I never searched for it". All pathology science is based in searching for it. We created gram staining dyes, scanners, tags, gold coated plates for electronic microscopes, DNA analysis... exactly for that. If there really is a microbiome living in each healthy brain, we should have found it 150 years ago.

j6m8 2y ago

Microbes are CRAZY. They're everywhere. Thermal vent-friendly microbes. Space-friendly microbes. Vacuum-resilient, heat-resilient, acid-resilient. Microbe-free-environment-friendly microbes [1]. It seems hard to imagine that a blood-brain barrier could really keep the brain sterile. We're lucky to live in a scientific era during which a "gut microbiome" is taken for granted (heck, even FDA-approved treatments depend on it! Google FMT, but don't click "images" from your work laptop), but it wasn't so long ago that we felt microbes were unlikely to live endogenously and harmlessly anywhere in the body. There were also some hypotheses (untested, if memory serves) that COVID-19 influenced olfactory neurons through direct infection. Don't tell the blood-brain barrier, but if I were a bacterium, the nasal palate would be my ingress strategy. Or maybe the gums or gut — one of the cranial nerves, certainly. [edit] I should clarify — covid is viral, not bacterial, but it does show that this is a potential entry vector. The central nervous system is incredibly complicated, and our symbiotic relationship with microbes is extraordinary. I think it does a disservice to bacteria to suppose they DON'T get involved in an organ :) [1] https://www.space.com/ryugu-asteroid-sample-earth-life-colonization https://www.space.com/ryugu-asteroid-sample-earth-life-colon...

pazimzadeh 2y ago
Our defenses are also crazy. For example, the inner mucus layer of the colon is able to keep trillions of bacteria at bay the vast majority of the time (unless there is inflammation or takeover by specific mucus-eating bacteria). Many of the proteins in the secreted mucus layers are still unknown in function, like FCGBP which comprises up to 40% of the protein content of mucus. The inner of the two Muc2 mucin-dependent mucus layers in colon is devoid of bacteria https://pubmed.ncbi.nlm.nih.gov/18806221/ https://pubmed.ncbi.nlm.nih.gov/18806221/ Bacteria penetrate the normally impenetrable inner colon mucus layer in both murine colitis models and patients with ulcerative colitis https://gut.bmj.com/content/63/2/281 https://gut.bmj.com/content/63/2/281 So I think without trillions of bacteria to exclude, in the absence of any other issues excluding bacteria from the brain seems pretty doable. Many viruses infect neurons, but they are way smaller than bacteria.