Runaway Endosymbionts: What are They? Well, I think this needs a bit of elaboration, don’t you? First of all, what exactly is a symbiont, much less and endosymbiont? Fair question. A symbiont is one of two or more organisms engaged in a symbiotic relationship. Symbiotic relations can be categorized as follows: predation, parasitism, commensalism, and mutualism. In predation, the relationship is short and violent and there is a winner and a loser. The same things applies with parasitism but usually without immediate death of one of the organisms. In fact, the best parasite is the one that causes the least damage to the host. Commensalism is where one organisms benefits without harming the other one. However, the most important of them all is mutualism, whereby all organisms involved benefit from the relationship. This is the stuff of which cells are made. Cells can coexist as either exosymbionts or endosymbionts. The former means these cells attach to one another in some way and the latter means one cell is ingested by another. Now that you know what an endosymbiont is, it is time to move on.
How can endosymbionts “run away”? From what are they running? At this point, let me drag out some pictures from my last two posts:
Do you see anything here that looks like it’s “running away”? In the first picture, glowing vesicles are streaming through tubular structures in multiple directions. In the second picture, blebs and tethered vesicles can be seen “escaping” from the nucleus. I have even seen a wriggling filament escaping from a nucleus. In the last picture, small circular elements are seen “flying away” from a main circular body as if their very “lives” depended upon it. So exactly what is going on here? Well, here is my interpretation of what may be happening: These structures are behaving like endosymbionts that are attempting to escape from a toxic environment, i.e., cell death. They are all different sizes, as if they are some kind of conglomeration of different kinds of endosymbionts; chaos and order all wrapped together as in real life. So how do these chaotic “endosymbionts” form? Again, it is probably a matter of chance and timing. Timing includes where they are in the cell cycle at the moment of cell death and what developmental phase they are in, i.e., how well differentiated they are and in what tissues. Suffice it to say that most or all of these structures are doomed because they have long lost any chance at autonomy by losing genetic material no longer required for their viability within the cell. Their only chance at survival is to infect a cell and bind to its DNA.