I suppose to a person with a sneeze fetish, the common cold would be a ‘good’ disease.
Hey bbeaty,
Ah, but the time scales involved are not the only reason I think it’s ridiculous to call organelles “diseases.”
What a bizarre statement. Who in their right mind would define a disease as “living things with their own genes and reproduction”? Is Huntington’s Chorea a disease? Of course it is. Is it a living thing with its own genes and reproduction? That statement doesn’t even make any sense.
Besides, it is only a half truth to claim that organelles reproduce, even “largely”, on their own. A large proportion of organellar genes have, over the 2 billion years they’ve been inside what we now call “eukaryotes”, migrated to the nuclear genome (cite). This means that, not only can the “host” not live without the organelle, the organelle cannot reproduce without the “host.” This is not semantics: it is a fallacy to claim that organelles and eukaryotic cells are separate organisms.
-Apoptosis
Organelles are not independent living things, and haven’t been for billions of years (since the eukaryotic lineage) They no longer encode all (or indeed most) of their own essential genes. Over time, they have lost those genes, and only those lines where the nucleus happened to acquire those genes, or compensatory equivalents, have survived.
No organelle could, even in theory or principle live independently. Their genomes are tiny and incomplete. Numerous organelle “diseases” exist, where a nuclear gene is damaged or deleted, and the, say, mitochondria are left to fend for themselves in some key protein. They don’t survive well, and neither does the person as a whole.
I fully believe many organelles once were independent organism, and indeed have been working off and on for 20+ years on a theory I call “endopredation” which explains numerous facts about not just organelles, but the nucleus (with its dual lipid bilayer nuclear membrane) itself as potentially more than just endosymbionts,. I feel they are remnants of an early era (at or before the first cyanobacterial stromatoliths 3.5-5 billion years ago) when the competition between unicellular organisms was fierce and remarkably clever (which is not to say that it still isn’t).
There is a huge amount of supporting biochemical data, much of which has been known for decades, but never synthesized into a single picture. Biochemical lineages such as the sterols of certain archaebacter (or whatever they are fashionably called these days, it’s been several years since my last cycle of active research on this) are only found today in eukaryotes (cells with nuclei) but are not found in surviving prokaryotes (cspecies without nuclei). Without going into tedious details, it’s possible that the eukaryotes are the result of endo-predators or parasites who usurped other species to serve as defensive and biochemical slaves (the cytoplasm) to themselves, (now the nucleus). Among the possible advantages are the (in evolutionary terms) near instant merging of two separate biochemical lineages. for example, the ribosomes of the cytoplasm might come from ancient bacteria that were far advanced on the pathway from RNAzymes (RNAs which act as enzymes, seen today in Tetrahymena) to protein enymes, and the efficiency of ribosomes would be a great boon to a usurping proto-nucleus microbe.
On the vast scales involved, it becomes an issue of pure imagination: we would not be anything at all (i.e. our entire lineage going back to the two-cell stage) without the organelles, and the organelles are mere remnants of extinct bacterial species (like the junk DNA leftover from archaic infections with now extinct viruses) In fact, I believe that not only those species, but their genera , families, orders, classes, phyla – and probably Kingdoms - are now extinct (During the 90’s the recognized ‘kingdoms’ exploded. It’s not longer limited to Animalia, Plantae, Prokaryota or even Archaebacter -yup, they aren’t just ancient, but they’ve been classified as their own kingdom for quite some time.)
If this sounds weird, just think of it this way: ALL organisms from 4-5 billion years ago bear only a faint resemblance to anything that survives today. Also, after a while, it becomes a bit like saying that some person’s great ^10th grandmother’s pure [ethnicity of you choice] genes were corrupted by an invading great ^10th grandfather. It’s irrelevant when both pure lineages no longer exist, and the hybrid is widespread today.
The word disease sort of means ‘not happy’ or ‘not at ease’ (dis-ease)
So there are no good diseases.
But I am being pedantic, I do know what you are getting at. I saw a program once about a guy with a mental disability that caused him to be euphoric all the itme.
I think you are referring to Simonides. He used a technique called memory palace. Not a disease.
How about E. coli in the intestines? They help digestion which is very pleasurable. It is probable that these were once virulent but have since become attenuated:
from here
This is also seen with diseases such as cytomegalovirus, herpes, human parvovirus, etc - i.e. a majority of the population carry these viruses but display no harmful effects.
Part of this could be a semantic question – many people define ‘disease’ as being something bad, and would call a situation that’s good for the host as ‘symbiosis’ . (Leaving aside genetic ‘diseases’ for now)
So recasting the OP : ‘Are there or could there be any organisms that are similar to disease-causing organisms but exist in a symbiotic relationship with humans?’
I vote for the E. coli and friends infestation of my gut. (or going further back, the mitochondrial infestation of my cells).
Remember, if it’s good for the host, it will spread, so if you include ‘unusual’ in your definition, examples will be hard to find.