57 posts tagged Life
Evolution depends on rare chance events, ‘molecular time travel’ experiments show
Chance events may profoundly shape history. What if Franz Ferdinand’s driver had not taken a wrong turn, bringing the Duke face to face with his assassin? Would World War I still have been fought? Would Hitler have risen to power decades later? Historians can only speculate on what might have been, but a team of evolutionary biologists studying ancient proteins has turned speculation into experiment. They resurrected an ancient ancestor of an important human protein as it existed hundreds of millions of years ago and then used biochemical methods to generate and characterize a huge number of alternative histories that could have ensued from that ancient starting point. Tracing these alternative evolutionary paths, the researchers discovered that the protein – the cellular receptor for the stress hormone cortisol – could not have evolved its modern-day function unless two extremely unlikely mutations happened to evolve first. These “permissive” mutations had no effect on the protein’s function, but without them the protein could not tolerate the later mutations that caused it to evolve its sensitivity to cortisol. In screening thousands of alternative histories, the researchers found no alternative permissive mutations that could have allowed the protein’s modern-day form to evolve. The researchers describe their findings June 16, online in Nature. “This very important protein exists only because of a twist of fate,” said study senior author Joe Thornton, PhD, professor of ecology & evolution and human genetics at the University of Chicago. “If our results are general – and we think they probably are – then many of our body’s systems work as they do because of very unlikely chance events that happened in our deep evolutionary past,” he added. Thornton specializes in ancestral protein reconstruction, a technique that uses gene sequencing and computational methods to travel backwards through the evolutionary tree and infer the likely sequences of proteins as they existed in the deep past. Through biochemical methods, these ancient proteins can be synthesized and introduced into living organisms to study their function. Thornton and others have previously shown that the evolution of modern-day proteins required permissive mutations in the past. But no one had ever investigated whether there were many or few other possible permissive mutations that could have happened, so it remained unknown how unlikely it is that evolution discovered a permissive pathway to the modern function. (via Evolution depends on rare chance events, ‘molecular time travel’ experiments show)
Life Magnified: The Alien Familiarity of the Cellular World
A new collection from the National Institutes of Health offers a zoomed-in perspective of the world.
Our universe is a vast and repeating tapestry of convergences. This how we experience it anyway, and in part because our brains are hardwired to recognize patterns. We can’t help but see the fractal echo of tributaries in a blown-up image of our own capillaries. And it makes sense that a network of Earth’s waterways might resemble a system of human blood vessels; it’s just not the sort of observation that most vantage points allow. Looking at something familiar from an unfamiliar perspective—often from very far away or from very close up—can be revealing this way. Such perspectives abound in science, where microscopes and telescopes allow us to access new worlds over extreme distances and through painstaking repetition. You can catch a glimpse of this world in a new exhibit curated by the National Institutes of Health called Life: Magnified, which includes remarkable scientific images—many come from NIH-backed projects—including a striking forest of gecko toe hair, the sunflower burst of a human liver cell, the fine spiderwebbing that creeps up blood vessel walls, and stunning solar systems of cells. The American Society for Cell Biology’s director calls it a “dazzling trip through the cellular world, which is both foreign and as close as [your] own skin.” (via Life Magnified: The Alien Familiarity of the Cellular World - Adrienne LaFrance - The Atlantic)
Milky Way may have 100 million life-giving planets
“It seems highly unlikely that we are alone.”
There are some 100 million other places in the Milky Way galaxy that could support life above the microbial level, reports a group of astronomers in the journal Challenges (open access), based on a new computation method to examine data from planets orbiting other stars in the universe. “This study does not indicate that complex life exists on that many planets; we’re saying that there are planetary conditions that could support it, according to the paper’s authors*. “Complex life doesn’t mean intelligent life — though it doesn’t rule it out or even animal life — but simply that organisms larger and more complex than microbes could exist in a number of different forms,” the researchers explain. The scientists surveyed more than 1,000 planets and used a formula that considers planet density, temperature, substrate (liquid, solid or gas), chemistry, distance from its central star and age. From this information, they developed and computed the Biological Complexity Index (BCI). The BCI calculation revealed that 1 to 2 percent of the planets showed a BCI rating higher than Europa, a moon of Jupiter thought to have a subsurface global ocean that may harbor forms of life. With about 10 billion stars in the Milky Way galaxy, the BCI yields 100 million plausible planets. The authors cite one study that suggests that “some exoplanets may be more optimally suited for life than Earth. … Such ‘superhabitable’ worlds would likely be larger, warmer, and older, orbiting dwarf stars.” “It seems highly unlikely that we are alone,” say the researchers. “We are likely so far away from life at our level of complexity that a meeting with such alien forms might be improbable for the foreseeable future.” (via Milky Way may have 100 million life-giving planets | KurzweilAI)
(via SFI Bulletin)
What life wants
Dead matter has no goals of its own, yet life is constantly striving. That makes it a deep puzzle for physics
The separation between sciences is crumbling. Nature doesn’t recognise disciplinary borders, and as we deepen our understanding, we see more of what these traditionally distinct branches of science have in common. There remain, however, curious hold-outs. Physics deals with the basic properties of matter and energy and how they interact. Chemistry asks how atoms get together to form more complex molecules and what effect this has on the resulting substances. What both have in common is that they study inanimate matter. Biology, on the other hand, studies living organisms. And here we encounter the central obstacle to seeing all of natural science as one big coherent whole. Inanimate matter seems to obey the laws of nature without exception and down to the last letter. Living things, by contrast, appear to have a will of their own. They are best understood — perhaps even best defined — by what might be called purposiveness. They try to do things, and while they cannot violate the laws of nature, they certainly can exploit them in order to realise their goals. You can’t say the same for inanimate matter.
Onward to Europa
The oceans of Jupiter’s ice worlds might be swimming with life — so why do we keep sending robots to Mars?
If Europa is alive, if some biology dwells within those dark waters, the implications would be even more staggering than finding life on Mars. Our gaze would turn to Jupiter’s Ganymede next, and to Callisto, along with Saturn’s Titan and Enceladus, and perhaps even the dwarf planets such as Ceres and Pluto, all of which also likely harbour substantial subsurface reservoirs, heated through some combination of tides and radioactive decay. (via It’s time to look for life in Europa’s ocean – Lee Billings – Aeon)
First lifeforms to pass on artificial DNA engineered by US scientists
Organisms carrying beefed-up DNA code could be designed to churn out new forms of drugs that could otherwise not be made
The first living organism to carry and pass down to future generations an expanded genetic code has been created by American scientists, paving the way for a host of new life forms whose cells carry synthetic DNA that looks nothing like the normal genetic code of natural organisms. Researchers say the work challenges the dogma that the molecules of life making up DNA are “special”. Organisms that carry the beefed-up DNA code could be designed to churn out new forms of drugs that otherwise could not be made, they have claimed. “This has very important implications for our understanding of life,” said Floyd Romesberg, whose team created the organism at the Scripps Research Institute in La Jolla, California. “For so long people have thought that DNA was the way it was because it had to be, that it was somehow the perfect molecule.” From the moment life gained a foothold on Earth the diversity of organisms has been written in a DNA code of four letters. The latest study moves life beyond G, T, C and A – the molecules or bases that pair up in the DNA helix – and introduces two new letters of life: X and Y. Romesberg started out with E coli, a bug normally found in soil and carried by people. Into this he inserted a loop of genetic material that carried normal DNA and two synthetic DNA bases. Though known as X and Y for simplicity, the artificial DNA bases have much longer chemical names, which themselves abbreviate to d5SICS and dNaM. In living organisms, G, T, C and A come together to form two base pairs, G-C and T-A. The extra synthetic DNA forms a third base pair, X-Y, according to the study in Nature. These base pairs are used to make genes, which cells use as templates for making proteins. Romesberg found that when the modified bacteria divided they passed on the natural DNA as expected. But they also replicated the synthetic code and passed that on to the next generation. That generation of bugs did the same. (via First lifeforms to pass on artificial DNA engineered by US scientists | World news | The Guardian)