Before looking at a more radical example whereby symbiogenesis with bacteria played a key role in the evolution of a certain metazoan lineage, I thought it a good idea to stress the significance of the terraformers.
The common perception of bacteria is that they are primitive, single-celled organisms. Yet they are not primitive; they are extremely sophisticated in many ways. That’s something most readers of this blog can probably agree with. But I would also argue that, on balance, it is also misleading to think of bacteria as single-celled organisms when, in reality, they are more like cells that are part of superorganism. They form a web of connections. We’ll explore that in future blog entries.
But for now, consider another common perception of bacteria – they are minor players and easy to ignore except when they cause disease. Wrong. Our existence is built on the back of bacteria. Consider a recent survey of the ocean’s biotic diversity:
marine microbes account for up to 90% of all ocean biomass and collectively weigh the equivalent of 240 billion African elephants.
240 billion African elephants. And it’s safe to say that the majority of this microbial biomass is bacterial. Consider this from “Prokaryotes: The unseen majority” by William B. Whitman, David C. Coleman, and William J. Wiebe:
Thus, the total amount of prokaryotic carbon is 60–100% of the estimated total carbon in plants, and inclusion of prokaryotic carbon in global models will almost double estimates of the amount of carbon stored in living organisms. In addition, the earth’s prokaryotes contain 85–130 Pg of N and 9–14 Pg of P, or about 10-fold more of these nutrients than do plants, and represent the largest pool of these nutrients in living organisms.
In fact, how many bacterial cells exist on the planet? Answer – 5 x 10^30
And as any microbiologist will tell you, these cells are found everywhere we find life, including places where bacteria are the only life forms.
So why is all this significant?
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