Our last common ancestor inhaled hydrogen from underwater volcanoes
LUCA likely fed on hydrogen and minerals from underwater volcanic vents. AF archive/Alamy Stock Photo
By Robert F. Service Jul. 25, 2016 , 11:15 AM
The chemical chain of events that led to the origin of life on Earth is likely forever lost to the mists of time. But some of our earliest ancestors—including the microbial Eve from which all modern cells descended—left behind traces in the genes they passed to their descendants. To track these shared genes, geneticists have surveyed nearly 2000 genomes of modern microbes. Now, researchers report that they’ve used this sort of genome mining to reveal new insights about the daily life of our last universal common ancestor, or LUCA. The results suggest that LUCA was a heat-loving microbe that fed on hydrogen gas and lived in a world devoid of oxygen, bolstering strong suspicions that life on Earth formed in and around hydrothermal vents such as those found near undersea volcanoes.
Today, the cells that make up all life on Earth are clustered into three broad groups: bacteria, archaea, and eukaryotes. The first two comprise prokaryotes—cells without a nucleus. A distant union between these two formed eukaryotes—cells with a nucleus that make up all the complex multicellular organisms including plants and animals.
Genetic studies to date have revealed some tantalizing clues about LUCA. Most evidence suggests that, like modern cells, LUCA stored genetic information using DNA. It also built proteins and used adenosine triphosphate as its currency for energy. But it has been harder for geneticists to know other details of LUCA’s lifestyle. One major complication: Microbes not only pass genes to their progeny, but also swap them among their neighbors in a process called horizontal gene transfer. This makes it hard to tell whether genes shared by separate microbes reflect a shared lineage or whether some bugs were just better at spreading their genetic material far and wide. And that makes it harder to pin down LUCA’s lifestyle.
To get closer to doing just that, researchers led by William Martin, an evolutionary biologist at Heinrich Heine University in Dusseldorf, Germany, took a more stringent approach to identifying genes that were likely inherited. Rather than looking for genes shared by a single species of bacteria and a single species of archaea, they searched for those shared by at least two species of bacteria and two of archaea. This gave them an initial count of some 6 million genes grouped into more than 286,000 related gene families. Further analysis revealed that only 355 of these gene families were broadly distributed across all modern organisms, and thus could be tracked from an ancestral species through all of its descendants. That made the 355 gene families likely LUCA candidates.
As Martin and his colleagues report in today’s issue of Nature Microbiology, these genes aren’t randomly scattered throughout modern organisms [ http://www.nature.com/articles/nmicrobiol2016116 ], but fall into distinct groups that reflect LUCA’s likely metabolism. Most notably, they reveal that LUCA was an anaerobe that grew in an environment devoid of the oxygen that most cells today require. That jibes with what scientists know about Earth 4 billion years ago, a period known as the late heavy bombardment. Not long after the planet’s formation, meteors and comets rained steadily down, the seas periodically boiled away, and the atmosphere lacked oxygen. The gene scans also show that LUCA was almost certainly a heat-loving “thermophile” that fed on hydrogen gas (H2), as others have proposed. Today, many microbes produce H2. But because LUCA preceded them, it would have had to belly up to a geological source of hydrogen, such as a hydrothermal vent like those found near an undersea volcano.
James Lake, an evolutionary biologist at the University of California, Los Angeles, calls the new work “remarkable” and “an important step forward.” Lake also notes that LUCA shares its lifestyle with two groups of modern microbes: clostridium, a genus of anaerobic bacteria, and methanogens, a group of H2-eating archaea. So even though the LUCA is long gone, its closest relatives may still be with us.
Study tracing ancestor microorganisms suggests life started in a hydrothermal environment Grand Prismatic Spring and Midway Geyser Basin from above. A speculatively rooted tree for rRNA genes, showing the three life domains Bacteria, Archaea, and Eucaryota, and linking the three branches of living organisms to the last universal common ancestor (the black trunk at the bottom of the tree). Note that the most modern models now place the origin of the eukaryotes within the archaeal lineage. Scanning electron micrograph of Clostridium difficile bacteria from a stool sample. July 25, 2016 https://theconversation.com/study-tracing-ancestor-microorganisms-suggests-life-started-in-a-hydrothermal-environment-62924 [with comments] [also at/images from http://phys.org/news/2016-07-ancestor-microorganisms-life-hydrothermal-environment.html ]
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Behold LUCA, the Last Universal Common Ancestor of Life on Earth Sully Vent in the Main Endeavour Vent Field in the northeast Pacific, similar to the environment in which LUCA would have lived. New discoveries suggest life likely descends from the inhospitable environment of deep sea vents July 26, 2016 http://www.smithsonianmag.com/smart-news/behold-luca-last-universal-common-ancestor-life-earth-180959915/ [with comments]
Wanna-Be Dino? Prehistoric Reptile Looked Like a Dinosaur
"All Species Evolved From Single Cell, Study Finds"
Sep 22, 2016 12:00 PM ET
Not all prehistoric animals that looked like dinosaurs were actually dinos, suggests a new fossil.
[inside, doesn't matter, see the video below] Image: The preserved remains of Triopticus (left) show the evolution of a thickened domed skull in the Triassic Period, 150 million years before the evolution of the famous dome-headed pachycephalosaur dinosaurs, such as Stegoceras (right). The background image shows the field site in Texas where WPA crews in 1940 found the curious fossils of Triopticus. Credit: Michelle Stocker
The newly identified reptile, described in the journal Current Biology, resembled pachycephalosaur dinosaurs that lived more than 100 million years later. Other extinct animals found with the reptile looked like later dinos too.
"Triopticus is an extraordinary example of evolutionary convergence between the relatives of dinosaurs and crocodylians and later dinosaurs that is much more common than anyone ever expected," co-author and project leader Michelle Stocker, a Virgnia Tech College of Science researcher, said in a press release. "What we thought were unique body shapes in many dinosaurs actually evolved millions of years before in the Triassic Period, about 225 million years ago."
Three Eyes dates to about 230 million years ago, according to the researchers. The reptile's partial skull was originally collected at a site called Otis Chalk near Big Spring, Texas .. http://www.seeker.com/can-texas-actually-secede-from-the-us-1888132808.html , by the Works Progress Administration in 1940.
President Franklin Roosevelt had initiated a monumental effort to put Americans back to work at end the Great Depression. With so much digging going on, numerous fossils were unearthed. In fact, so many fossils were found during such a short time span that several of them were just put into storage uncleaned.
Such was the case for Three Eyes, whose skull was eventually sent to the Texas Vertebrate Paleontology Collections in 2010. It is there that Stocker and her team rediscovered and analyzed the specimen.
WATCH VIDEO: What Color Were the Dinosaurs? [insert You Tube of embedded video, 'cept it looks to be 8s longer]
"CT scanning showed us that the similarity of Triopticus with the much later dome-headed pachycephalosaur dinosaurs was more than skin deep, extending to the structure of the bone and even the brain." co-author Lawrence Witmer of Ohio University's Heritage College of Osteopathic Medicine said.
It was not a coincidence that the reptile and dinosaurs resembled each other.
"After the enormous mass extinction 250 million years ago, reptiles exploded onto the scene and almost immediately diversified into many different sizes and shapes," co-author Sterling Nesbitt of Virginia Tech said. "These early body shapes were later mimicked by dinosaurs."
"The Otis Chalk fauna is an amazing single snapshot of geologic time where you have this extraordinary range of animal body plans all present at the same time living together," Stocker said. "Among the animals preserved in the Otis Chalk fauna, Triopticus exemplifies this phenomenon of body-shape convergence because its skull shape was repeated by very distantly-related dome-headed dinosaurs more than 100 million years later."
Other studies over the past several years indicate that dinosaurs, like these distant cousins from the Triassic Period .. http://www.seeker.com/triassic-crocodile-relative-unearthed-in-new-mexico-2001287320.html , were all reptiles. Reptiles rapidly evolved in terms of numbers of species soon after the greatest mass extinction of all time on Earth, at the end of the Permian Period.
[ hmm, lolol, there is a bit more here, but when i try to copy it it changes the text and the image above, then doing that again didn't change it back .. sorta weird, still haven't figured it out .. i've never seen anything like it before ]
.. so there you go .. latest hypothesis is all from a single cell .. if that's hard to grasp have another or even just a peek at the one this post replies to .. it's all very cool and much more interesting than Adam and Eve could ever be .. though guess that idea would have been extra engrossing for some way back .. oh, sorry it still has some transfixed, doesn't it .. such a shame that ..
ps: that hmm, just above will probably be easy for others .. not unusual it's just me .. lol
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