According to new research, ancient microbes were performing photosynthesis as much as one billion years earlier than previously thought.
Photosynthesis — the ability to convert the sun's rays into usable energy, and in the process produce oxygen — kickstarted early evolution, paving the way for more complex organisms. But scientists haven't been able to agree on when organisms first developed the ability.
Many scientists believe anoxygenic photosynthesis evolved earliest. Anoxygenic photosynthesis involves the splitting of hydrogen sulfide, or minerals such as iron, and doesn't produce oxygen. The theory holds that cyanobacteria capable of performing oxygenic photosynthesis, which split water and yields oxygen, came later, some 2.4 to 3 billion years ago.
The research of Tanai Cardona suggests otherwise.
Instead of searching for signs of oxygen in ancient rocks, the traditional method for finding ancient proof of photosynthesis, Cardona explored the biomechanical systems responsible for photosynthesis in primitive microbes — so-called photosystems.
Both oxygenic and anoxygenic photosystems rely on an enzyme called Photosystem I, but core compositions of the enzyme are different in each system. Cardona hypothesized that if he could determine when the enzyme evolved two divergent functions, he could estimate when oxygenic photosynthesis first emerged.
His analysis, published this week in the journal Heliyon, showed the genetic differences first emerged 3.4 million years ago, before cyanobacteria are thought to have first arrived in the oceans.
"This is the first time that anyone has tried to time the evolution of the photosystems," Cardona said in a news release. "The result hints towards the possibility that oxygenic photosynthesis, the process that have produced all oxygen on earth, actually started at a very early stage in the evolutionary history of life — it helps solve one of the big controversies in biology today."
As part of his research, Cardona measured the rate of evolution of photosystems from the emergence of cyanobacteria until today. When plotted backwards, the slow rate of evolution suggests photosystems first emerged before Earth was born. The calculations suggest photosystems may have evolved more rapidly when Earth was young and hot.
"There is still a lot we don't know about why life is the way it is and how most biological process originated," said. Cardona. "Sometimes our best educated guesses don't even come close to representing what really happened so long ago."
Ancient gut microbe allowed turtle ants to abandon offense and focus on defense
Washington (UPI) Mar 6, 2018 –
Turtle ants have adopted a largely defensive posture and abandoned the offensive tendencies of their relatives. New research suggests the strategic shift was made possible by their partnership with 46 million year-old gut bacteria.
More than a decade ago, Drexel University scientists realized ant species with nutrient-poor diets also hosted unique bacterial symbionts. To better understand these relationships, researchers decided to take a closer look at turtle ants, a group of species belonging to the neotropical genus Cephalotes.
In the lab, scientists fed the ants urea, the main waste ingredient in urine. They also fed them antibiotics to kill the bacteria living in ants' digestive system. Without the help of their bacterial symbionts, the ants were unable to consume sufficient levels of nitrogen.
Animal waste, including urine and feces, is rich in nitrogen, but the nutrient is inaccessible to most animals without the help of microbes.
With the help of their microbial partners, turtle ants can subsist on poor diets. As a result, they no longer compete with other ants for high-quality meals. They've abandoned the strong lower mandible that allows other ants to rip apart larger invertebrates. They've also lost their ability to sting.
In the place of offense, turtle ants have invested in defense, evolving thicker armor and a "specialized caste of adults that use their heads to plug the entrances of their hollow tree branch nests," according to Drexel researcher Jacob Russell.
"That armor may be possible due to the large contributions gut microbes make to their nitrogen budgets," Russell said in a news release.
The ants are very protective of their gut microbes. They use anal secretions to share their microbes with one another and have evolved a fine-mesh filter in the digestive tract to serve as a protective barrier.
"This has likely helped to reinforce the integrity of these ancient bacterial communities," Russell said.
Russel and his colleagues detailed their study of turtle ants in the journal Nature Communications.
"This work illustrates that members of complex communities can evolve together, laying the groundwork for future research on how these organisms evolve in response to reliable partnerships," Russell said.
