The mission of the Flock app is quietly subversive: to encourage users to ditch their screens and explore the wonderful world of birding
On a brilliantly bright afternoon in his gallery and studio in Bolinas, a small town on the northern California coast, Keith Hansen was putting the finishing touches on a watercolor of an almost improbably flamboyant painted bunting.
With an ultra-fine sable brush, he made a few intricate additions to the cobalt blue plumage on the bunting’s head, and, satisfied with his work, slipped the watercolor into a stout binder that every few days welcomes a new addition.
An international research team has uncovered how LUCA, the last common ancestor of all life on Earth, split into the first two branches of organisms—bacteria and archaea—allowinglife to thrive innew conditions and spread to other biomes.
Scientists from the Institute of Molecular Evolution at Heinrich Heine University Düsseldorf (HHU) led the research, revealing their findings in a recent paper published in Science Advances, investigating these early cells’ metabolisms.
The team discovered that the chemical reactions and energy sources behind these two types of cells told unique stories of separate evolutions, in new work that sheds light on the primordial processes that gave rise to some of Earth’s first free-living cells.
Life on Earth Begins
Roughly four billion years ago, life on Earth emerged as the first cells formed, most likely at hydrothermal vents, before evolving to explore new biomes.
“We would see two very different kinds of cells emerging, pioneer bacteria and pioneer archaea, making their first attempts at life outside the confines of a hydrothermal vent,” said lead author Natalia Mrnjavac, a biologist at the University of Düsseldorf.
The new study investigated protein structures, chemical reactions, and genomes involved in the evolution of these early free-living cells.
“These comparisons are giving us unprecedented insights into the phase of evolution when metabolism catalysed by enzymes was arising from spontaneous reactions catalysed by metals in the Earth’s crust,” said senior author William Martin, a Düsseldorf biologist.
Metabolism and Evolution
Among the new work’s major findings is a consideration of the entire set of 420 chemical reactions involved in metabolism that produce amino acids, RNA bases, and vitamins from the raw materials of hydrogen, ammonia, and carbon dioxide.
These reactions are preserved for modern researchers inside the genetic code, allowing the team to make a surprising discovery: about half of LUCA’s reactions were catalyzed by environmental metals instead of enzymes produced by the organism itself.
“Metals that naturally occur in hydrothermal vents can replace a surprisingly large number of enzymes in metabolism,” said co-author Harun Tüysüz, an inorganic chemist from the Max-Planck-Institut für Kohlenforschung and the IMDEA Materials Institute in Madrid.
In this study, the team reconstructed catalysis evolution from metal-only to a metal-enzyme hybrid present in LUCA, and finally to the divergence of the bacterial and archaeal lineages. This evolution helped life move on from the hydrothermal vents inhabited by the first cells by replacing the inorganic catalysts provided by that environment with new enzymes.
“We can see cases where the ancestors of bacteria and archaea independently evolved structurally distinct enzymes to catalyse the same essential metabolic reaction,” Mrnjavac explained, adding that “such parallel inventions could have paved the way to the independent emergence of free-living bacteria and archaea.”
The Energy for Life on Earth
A primary question involves what supplied the energy driving metabolic reactions in early life on Earth. A compound named ATP is the primary metabolic driver in most organisms today, but it comes from enzymes and is not present in hydrothermal vents. The researchers identified a new energy source in palladium, a natural catalyst used by chemists and also plentiful in hydrothermal vents.
“When we react phosphite, a form of phosphorus that naturally occurs in hydrothermal vents, with organic compounds, we get metabolic phosphorylation reactions overnight in water. Phosphite and palladium replace ATP and enzymes; it’s amazing, and it makes early evolution a lot easier to grasp,” Schlikker said.
Understanding the interconnection between so many reactions presents a significant mathematical challenge. For this reason, the team included not just biologists, but network scientists tasked with ordering the reactions by their complexity, which the researchers hoped would indicate the sequence in which they evolved. Using a machine learning algorithm, the team discovered that a clear order did appear to exist.
“The new data leave only one conclusion,” Martin concluded. “The bacteria and archaeal lineages made the transition to the free-living state independently. Only free-living cells are alive.”
“Let’s call it by name,” Martin added. “We are looking at one origin of the genetic code, but two origins of life.”
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org.
The biblical definitions of heart, mind, intellect, body and soul are discussed. I expand the discussion to the immortality of the soul and whether or not an AI machine can ever have or possess a soul.
A bank of fog might seem gloomy. But that mist may carry an unexpected community of environmental helpers. Ground-dwelling clouds can house bacteria that clean the air, a new study finds.
Microbes can find air a harsh place, notes Kathleen Weathers. Temperatures can fluctuate broadly. And even in fog, there can be a high risk of drying out. A fog scientist, Weathers works at the Cary Institute of Ecosystem Studies in Millbrook, N.Y. But, she adds, fog hosts many things needed for those microbes to “make a living.” These include moisture, nutrients and comfortable temperatures.
Yet until now, scientists hadn’t known microbes could actually live there, says Weathers, who did not take part in the new work.
It took Thi Thuong Thuong Cao, a chemist who loves hiking on foggy mountainsides, to show microbes not only can live in fog, but also grow and reproduce.
Collecting clouds
As a chemist, Cao wondered what might be inside fog droplets. At first, she focused on their chemistry. Soon, though, she teamed up with other scientists to see what microbes might hitchhike in fog — and what they might be doing.
At the time, Cao was a graduate student at Arizona State University in Tempe. Part of her team traveled to Pennsylvania, where another team member was based. The area had great spots to collect fog.
This team focused its hunt on a special type of low-lying cloud: radiation fog. It forms at night when the ground cools and then lowers the air’s temperature. Cooler air can’t hold much water. So it sheds the excess into the air as small droplets, creating fog.
Radiation fog doesn’t roll in. Instead, it forms in place. So any microbes should be local, not ones carried in from elsewhere.
Over about two years, the team collected samples of water from 32 “fog events.” They used a device called a cloud-water collector. It pulls air into a chamber containing strings.
Researchers assembled this setup in a Pennsylvania field to collect fog samples. They were looking to capture not only fog but also anything that might be living in the airborne water droplets.T.T.T. Cao
As fog condenses on the strings, it forms droplets that drip into a bottle below. The scientists collected up to 200 milliliters (about 7 ounces) of fog water per event. That’s roughly the volume of a juice box. They also collected samples of the air in between the fog droplets. They trapped similar air samples before and after fog events.
The fog samples housed a multitude of microbes. In fact, fog water is about as densely populated with microbes as ocean or lake water. When examined under a microscope, many fog-water microbes seemed to have been dividing when they were collected. That led the researchers to conclude the microbes had been growing in the fog.
Next, the team extracted the fog-dwellers’ RNA, a type of genetic information. Cao’s team compared these types of genetic maps to those in a database on known microbes. That helped them identify the fog’s inhabitants.
An average of 188 unique genetic patterns showed up in each fog event. Each represented a unique type of bacteria. The communities of microbes present were similar across all fog samples. But they differed quite a bit from those found in air without fog.
Cao and her team shared their findings in mBio on May 22.
Their analyses showed Methylobacterium was the most abundant microbe in fog water. It accounted for up to half of all microbes present.
To grow in fog, the team reasoned, those Methylobacteria must have found something in it to eat. This microbe is known to consume carbon-containing chemicals, such as formaldehyde.
Researchers grew colonies of Methylobacterium in this dish, feeding them only formaldehyde, a toxic chemical. “[T]hey have [a] pink pigment,” says Thi Thuong Thuong Cao. “They’re really cute.”T.T.T. Cao
Formaldehyde is a common and toxic air pollutant. Breathing it can cause harm. Some formaldehyde comes from natural sources, such as rotting plant materials. Human activities, such as construction and burning fossil fuels, also release it. It’s even one of the chemicals that makes cigarette smoke harmful.
Methylobacteria are well suited for dealing with this chemical, Cao says. “They can survive formaldehyde at a concentration higher than other bacteria [can].” They break it down hundreds of times faster than other microbes, too.
Her group measured formaldehyde in freshly collected fog water. Over several hours, levels of the chemical fell surprisingly fast.
The researchers also isolated Methylobacterium from fog water and then grew it on its own. These bacteria were able to quickly remove formaldehyde when exposed to an artificial fog water containing the chemical.
It disappeared so quickly, in fact, that the bacteria couldn’t have used it all for growth. The microbe may break the chemical down as well as eat it, the team concludes. Such a strategy might keep formaldehyde from reaching toxic levels.
This all seems to confirm Methylobacterium can remove formaldehyde from fog. The researchers don’t yet know how the bacteria might affect air quality. But their new data now point to fog as a potential ecosystem.
Fog can transport water and microbes across a landscape. These data now suggest that as it does, it may play a role in shaping the chemistry of the environment.
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