Your link to Lynch and Marinov is currently incorrect. However I also don’t understand whether what they say matches with your post:
the energetic burden of a gene is typically no greater, and generally becomes progressively smaller, in larger cells in both bacteria and eukaryotes, and this is true for costs measured at the DNA, RNA, and protein levels. These results eliminate the need to invoke an energetics barrier to genome complexity. … These results indicate that the origin of the mitochondrion was not a prerequisite for genome-size expansion.
Yes, welp, I considered getting into this whole debate in the post but it seemed like too much of an aside. Basically, Lynch is like, “when you control for cell size, the amount of energy per genome is not predictive of whether it’s a prokaryote or a eukaryote.” In other words, on his account, the main determinant of bioenergetic availability appears to be the size of the cell, rather than anything energetically special about eukaryotes, such as mitochondria.
There are some issues here. First, most of the large prokaryotes are outliers like Thiomargarita, in the sense that they have expanded their energy without expanding their functional volume. However, their genomes are still quite small, which means that their “energy/genome” will be large. Eukaryotic cells of the same size have waymore energy and way longer genomes, making their “energy/genome” roughly equivalent to the large prokaryotes.
Second, Lynch’s story is that strong selection keeps bacterial genomes short. The main reason that bacteria have strong selection is because there are so many of them, and there are so many of them because they’re so small. But why are they so small? It seems like an obvious contender is Lane’s story about them being energy bottlenecked by their surface area. So, in my opinion, these two hypotheses are synergistic and my best guess is that they’re both part of the story.
Your link to Lynch and Marinov is currently incorrect. However I also don’t understand whether what they say matches with your post:
Ah, thanks! Link fixed now.
Yes, welp, I considered getting into this whole debate in the post but it seemed like too much of an aside. Basically, Lynch is like, “when you control for cell size, the amount of energy per genome is not predictive of whether it’s a prokaryote or a eukaryote.” In other words, on his account, the main determinant of bioenergetic availability appears to be the size of the cell, rather than anything energetically special about eukaryotes, such as mitochondria.
There are some issues here. First, most of the large prokaryotes are outliers like Thiomargarita, in the sense that they have expanded their energy without expanding their functional volume. However, their genomes are still quite small, which means that their “energy/genome” will be large. Eukaryotic cells of the same size have way more energy and way longer genomes, making their “energy/genome” roughly equivalent to the large prokaryotes.
Second, Lynch’s story is that strong selection keeps bacterial genomes short. The main reason that bacteria have strong selection is because there are so many of them, and there are so many of them because they’re so small. But why are they so small? It seems like an obvious contender is Lane’s story about them being energy bottlenecked by their surface area. So, in my opinion, these two hypotheses are synergistic and my best guess is that they’re both part of the story.