Endosymbiont Puns

Abstract

An emerging frontier in synthetic biology involves the engineering of interspecies relationships, one of which could result in the development of novel organelles. The endosymbiotic theory is the most widely accepted model for the evolutionary origin of mitochondria and chloroplasts, asserting that these organelles descended from free-living bacteria. Imitating this process experimentally, which we refer to herein as directed endosymbiosis, could enable the development of an entirely new class of organisms with synthetic organelles. In this review, we discuss principles and strategies for directed endosymbiosis and highlight current developments. We also describe several bacterial species as candidates for converting into organelles that would have interesting applications.

https://www.sciencedirect.com/science/article/pii/S2452310020300330

View Poll

To preface: I am but a humble high school biology student, but have done my best to understand the (many, many) processes of biology at a level appropriate to my course. The aforementioned course is an AP course (Advanced Placement, for those outside North America), and as such I have a deeper understanding than your typical Bio student, which I hope to utilise to make my point here. Also, this post presumes that the reader has a preexisting knowledge of biology and knows the definition of many words specific to biology, but if any reader does not, I would be happy to provide a definition/brief synopsis of a process.

I have studied life in order of gradually increasing complexity, begging at the molecules essential to life and progressing up to the organisation of ecosystems and the biosphere as a whole. All of it fundamentally supports the idea of evolution, but one thing I found especially interesting was endosymbiont theory.

Endosymbiont theory states that mitochondria and chloroplasts and other plastids came about as a result of a larger cell engulfing a smaller one--capable of aerobic cellular respiration--that managed to avoid digestion and proved as an asset to the larger cell. Here is a graphic that explains it quite well.

The proof for this theory abounds:

1. New mitochondria and plastids form through binary fission in a manner very similar to prokaryotes. Here is a graphic showing the difference between binary fission and mitosis (meiosis is included as well, a process that is entirely absent in prokaryotes)
2. If you remove the mitochondria and/or plastids from a cell, the cell is unable to replace them, strongly suggesting that they do not originate from the cell itself.
3. Mitochondrial and plastid ribosomes are more similar to the ribosomes (the organelles that make protein using mRNA transcripts) of bacteria than the ribosomes of the cells that contain them [source]
4. Some mitochondria and plastids contain circular DNA that closely resembles bacterial DNA in structure [source] *~~(this source also shows why organelle genomes are much smaller than what their historical, free-living counterparts would have been, due to lateral DNA transfer o

I am worldbuilding a human civilization that was transplanted to Mars around 300 000 years ago by a Precursor civilization. That human civilization happened to develop higher imaginative culture and thus developed innovations way earlier than Earth humans did, and actually that more innovative genetics was transplanted back to Earth by these Precursors.

So the Martian developed a high civilization long long time ago with the Precursors acting as sages and councilors to the rulers of city states. Martian Homo sapiens also developed with the guidance of the Precursors genetic and biological technologies. Currently I am thinking that they developed symbionts, both larger and also microscopic ones.

Endosymbionts are for example the mitochondria of the cells, that are likely bacteria that became symbionts with eukaryotic cells. What other kinds of symbionts could there exist? What kind of abilities would those symbionts give to their carriers?

And yes, there is influence from S.M. Stirling in my worldbuilding.