Enjoy this lecture, as it echoes many of the points i have made on this blog:
I’ve long suggested that life is a form of carbon-based nanotechnology, as the more we learn about the cell, the more sophisticated it becomes. Doubt me? Take 30 minutes and listen to the following lecture by microbiologist Lucy Shapiro as she describes how various events in the cell cycle in the simplest of cells is carried out. Among other things, you’ll learn about the importance of location and organization inside bacteria, you’ll learn that the bacterial chromosome is laid out in space in an organized fashion, you’ll see the ingenious method the cell uses to target the site where it splits into two, and see how epigenetics is used to control the whole process. Or at the very least, you’ll feel a little bit smarter for investing that half-hour of your life. 😉
I’ve long found it fascinating that every living thing on this planet can be cleanly split into two categories – prokaryotes and eukaryotes. The prokaryotes consist of all the bacteria while the eukaryotes include animals, plants, fungi, and various protozoa. The core life processes of the two cells are much the same, being built around the triad of proteins, RNA, and DNA, relying on the ribosome to build the proteins that synthesize everything else, including RNA and DNA, using ATP as the primary energy currency, and using lipid bilayer membranes to compartmentalize. So what makes the two cell plans so different?
Below is a nice figure that helps you answer this question.
As you can see, there are two primary differences: size and level of compartmentalization. Typical eukaryotic cells are much larger than bacteria and show a much more extensive level of compartmentalization given the numerous membrane-bound organelles and membranous folds.
Yet a question to ponder is why there are two cell types and only two cell types? The non-telic perspective would explain this (away?) as simply an artifact of a contingent past. There is no reason to ponder the question “why?” It just happened that way. But the telic perspective allows us to think of these two cell plans at a level that runs deeper.
As I have argued before, one key to the success of bacteria-as-terraformers is their ability, as single-celled organisms, to network with each other both physiologically and genetically. Well, recent evidence strongly suggests that such connections also include charitable behavior, where certain cells come to the aid of their neighbors:
Humans are capable of great charity, taking hits to their bank accounts and bodies to benefit their peers. But such acts of altruism aren’t limited to us; they can be found in the simple colonies of bacteria too.
Bacteria are famed for their ability to adapt to our toughest antibiotics. But resistance doesn’t spring up evenly across an entire colony. A new study suggests that a small cadre of hero bacteria are responsible for saving their peers. By shouldering the burden of resistance at a personal cost, these charitable cells ensure that the entire colony survives.
Read the rest about this eye-popping study here.
You have probably heard this story by now:
But now researchers have discovered a bacterium that appears to have replaced that life-enabling phosphorus with its toxic cousin arsenic, raising new and provocative questions about the origins and nature of life.
News of the discovery caused a scientific commotion this week, including calls to NASA from the White House asking whether a second line of earthly life has been found.
Whether or not the bacteria actually replace phosphorus with arsenic is something that will eventually be sorted out. But for now, we can be confident that no “second line of earthly life has been found.”
“This is different from anything we’ve seen before,” said Mary Voytek, senior scientist for NASA’s program in astrobiology, the arm of the agency involved specifically in the search for life beyond Earth and for how life began here.
“These bugs haven’t just replaced one useful element with another; they have the arsenic in the basic building blocks of their makeup,” she said. “We don’t know if the arsenic replaced phosphorus or if it was there from the very beginning – in which case it would strongly suggest the existence of a shadow biosphere.”
Yes, we do know it wasn’t there from the beginning. How?
No, not chemical connections.Not genetic connections. Not conceptual connections. How about electrical connections?
Deep on the ocean floor, colonies of bacteria appear to have connected themselves via microscopic power grids that would be the envy of any small town. Much remains unknown about the process, but if confirmed the findings could revolutionize scientists’ understanding of how the world’s smallest ecosystems operate.
Oxygen-breathing bacteria that live on the ocean bottom have a problem. Those sitting atop the sediment have ready access to oxygen in the water but not to the precious mineral nutrients that lie out of reach a centimeter or so below the ground. Meanwhile, those microbes that live in the sediment can access the nutrients, but they lack oxygen. How do both groups survive?
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?