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Note: This question assumes an earth-like biology.

Could a microbe (probably virus) be created that transformed humans into plants? What I mean by this is that the microbe would take human cells, and slowly, over time, transform them into plant cells. Like the new plant would retain a human like shape, and possibly be a new species of plant, i.e. a human plant. The human (i.e. the human's consciousness) would die in the process, but before the human died he/she would start having plant like tendencies. These would include being attracted to sunlight, drinking lots of water, and eating less food. These new tendencies would lead to the human being a suitable place for a plant to grow, when it eventually created roots and killed its human host. There would be a short stage where both the human and the plant were alive, likely during this stage, the human would not be able to move (lower body would be plant like), and quite possibly would be insane.

So, could such a microbe exist under earth-like biology? And would there be multiple variants of the microbe, with each variant producing a different kind of plant?

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  • $\begingroup$ A "human plant" or "Hplant" if you will. $\endgroup$ – mechalynx Oct 5 '14 at 11:52
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    $\begingroup$ @ivy_lynx :D I'm really asking this because I'm looking to bio-engineer one, but they rejected the question at Biology.SE. So yeah, that's its name. $\endgroup$ – DonyorM Oct 5 '14 at 11:53
  • $\begingroup$ Gives "vegetable state" a whole new meaning! (ok I'm going to stop now, just can't resist these :P - I just hope you don't get an answer saying that "opiate based viruses" would work xD). Also, does it have be viruses? Can it be bacteria or amoebas or something? $\endgroup$ – mechalynx Oct 5 '14 at 12:25
  • $\begingroup$ Sure, changing it to microbes, virus were just what came to mind first. This isn't based on a story or anything, I just wondered. $\endgroup$ – DonyorM Oct 5 '14 at 12:31
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In principle, host cells can be changed quite significantly by a virus. A very common unwanted change triggered by viruses is cancer. The Wikipedia article on Viral transformation discusses some details

The biggest problem with a viral replication mechanism for a complex living thing, such as a plant, would be delivering enough DNA to describe the new form. Most plants have far too much DNA needed to describe then that would fit inside a simple virus. DNA would need to describe the chemicals needed to overcome the host's immune system and transform/develop the new organism, although that is probably no more than would be required to define the growth of a plant from scratch - at least this virus/plant would have a physical scaffold.

In numbers, the most complex known viral particles are known as "Megavirus" and can contain over a million base pairs of DNA. Whilst a relatively simple plant has 135 million base pairs.

If you can hand-wave this discrepancy, and the unlikely natural lifecycle of this organism, then I think that on the purely physical and chemical level, this is feasible.

If you extend this to other microbes, I think the nearest real-world example might be Anthax, which essentially changes a complex creature into goo, ready to be taken up again by another creature. Not quite the build you are looking for, but if you imagine perhaps a symbiosis between Anthrax and a plant which benefits from the extra nutrients and could produce very small spores that hitched a ride alongside, you might have a pathway to a single rather nasty plant/microbe parasite. Add a little sci-fi or handwaving to make the transform a little more grotesque and/or whilst alive, and you could get very close to your imagined parasite.

In terms of altering mental state, there is a well known fungus that infects ants and makes them climb up high to get the best spread of spores later. There are also other parasites that appear to take over their host's behaviour, although this is most likely by working with existing drives and behaviours to the parasite's advantage, as opposed to a wholesale transform.

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  • $\begingroup$ Does this answer change if it could be any microbe? $\endgroup$ – DonyorM Oct 5 '14 at 12:33
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    $\begingroup$ @DonyorM: I think altering host's cells in place requires a viral mechanism. Although consuming host and replacing with own material is possible (and some real-world parasites do this) $\endgroup$ – Neil Slater Oct 5 '14 at 12:51
  • $\begingroup$ Microbes would have the advantage of being able to store enough DNA to form the plant stage. They would either need to have a symbiotic virus to rewrite the host cells or would need to consume and replace them though. $\endgroup$ – Tim B Oct 5 '14 at 14:40
  • $\begingroup$ The plot of "The Last of Us" hinges on human cordyceps. It is, needless to say, utterly disturbing. $\endgroup$ – World Engineer Oct 5 '14 at 18:53
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    $\begingroup$ You wouldn't need to directly affect the host's behavior all that much. If you became capable of photosynthesis and incapable of digesting food, you would probably start acting a lot like a plant on your own. $\endgroup$ – octern Oct 5 '14 at 21:20
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Speculations aside, transformation into plant is possible at the cell level if the cell swallows and retains another photosynthetic organism that becomes useful. This can happen for a single cell, or some simple multi-cellular organism. Initially this is just infection, later genetic transformation may happen, moving photosynthetic genes into the host genome. This is how plants actually originated. Not a transformation by virus; a whole working machine of photosynthesis have been swallowed as food but ... stayed operational!

An infection that makes the skin green and photosynthetic, and is not deadly, and immune system does not fight? If this is a science fiction, who knows...

However human likely cannot survive with existing habits feeding just on sunlight. The skin area is not sufficient. If evolution would press on surviving on light only, various adaptations to use less energy and add the surface should occur. Move less, drop the body temperature by ten degrees at least and maybe more and bigger ears?

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Rather than changing the DNA of an existing cell and further having it change into a rather different cell, it could replace the cells one by one. A plant, growing vegitatively, consumes a host cell and replaces it with one of its own that is sort-of useful in the same tissue, preserving the life of the host so it continues to use its animal abilities to gather food and find shelter, and prevent a sudden rotting body from being consumed by decay bacteria and carrion feeders.

Ultimatly it could be symbiotic like a lichen.

Plant cells have much much more DNA, so let them do the work rather than somehow morphing an existing cell. A cell can replicate. Break down the other into raw material and then use the substance to make your daughter. From an observer's point of view, it doesn't matter if the cell is changed gradually while still working the whole time, or completely taken apart and rebuilt.

To transform rather than just rotting in the normal way, maybe the plant infiltrates the cell and eats it from the inside, and keeping the old tissue function like a guest operating system in a virtual machine.

Note that plant cells are different from animal cells. They have cell walls and various architectural differences.

Now if this transformer germ is engineered nanotechnology, then it could have a well planned program stored compactly in the DNA, and use a robust communications network between cells and download new code.

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