Archaebacterial species are among the first of their kind to colonize Earth

A species of bacteria that lived 407 million years ago likely flourished among early land plants.

Detailed 3D reconstructions of fossils discovered in Scotland are helping scientists understand more about how microbial life influenced early terrestrial ecosystems.

Cyanobacteria evolved early in our planet’s history and played an important role in shaping life as we know it.

These tiny microorganisms have been well documented in marine rocks, but scientists are trying to understand more about how they first colonized land.

Langiella scourfieldii is a species of cyanobacteria that is part of the Hapalosiphonaceae family and grew among early land plants more than 400 million years ago in the Early Devonian.

A new study published in iScience It reveals that L. scourfieldii is the oldest Hapalosiphonaceae species known to have colonized lands. It would have thrived in soil, fresh water and hot springs, as its living relatives do today.

“With the 3D reconstructions, we were able to see evidence of branching, which is a feature of the cyanobacteria Hapalosifonas,” says Dr. Christine Strollo-Deren, a research scientist at the museum and lead author of the study. “This is exciting because it means that these are the oldest cyanobacteria from this species.” The kind found on Earth.”

What are cyanobacteria?

Cyanobacteria are an ancient group of microorganisms. Their fossils are among the oldest ever discovered, with the oldest widely accepted dating back to about 2 billion years ago.

Today it is one of the largest and most important groups of bacteria. They live in and around aquatic environments almost everywhere on Earth, including oceans, fresh water, moist soil, and even Antarctic rocks.

Although they are small and single-celled, they often grow in colonies large enough to be seen with the naked eye, and are known for their broad blooms that turn the surface of the water blue-green.

These microorganisms played an important role in shaping the evolution of life. They carry out photosynthesis in a similar way to plants and are responsible for helping to create an oxygen-rich atmosphere.

About 2.4 billion years ago, masses of photosynthetic cyanobacteria began the Great Oxygenation Event, when oxygen began to replace other gases such as methane in the atmosphere. This led to what many scientists describe as the first mass extinction on Earth as organisms that had adapted to anaerobic life began to die out.

Cyanobacteria probably originated in freshwater environments, so scientists believe they began colonizing lands early in their history.

“In the Early Devonian, cyanobacteria played the same role they do today,” Christine says. “Some organisms use them for food, but they are also important in photosynthesis. We knew they were already around when plants first began to colonize Earth, and may have competed with them for space.”

How was Langella scorveldi discovered?

L. scourfieldii was first discovered in 1959 along with two other species from a piece of rock found at the Rhynie Chert excavation site in Aberdeenshire.

The original descriptions were based on specimens in museum collections, but more recently, similar specimens discovered in the collections of the Sorbonne University in Paris have been found to be of the same species.

“The three species of cyanobacteria that were described in 1959 were created from a small piece of rock that is difficult to image and study,” Christine says.

“Fortunately, we have found new samples of Rhynie Chert containing cyanobacteria that we can study in more detail using confocal microscopy.”

One of the main characteristics of this type of bacteria is the presence of what is known as “true branching”. This occurs when individual bacteria grow side by side in a single line, with some of the lines breaking off in different directions to form a branching structure.

While cyanobacterial remains are relatively common in the Rhynie Chert, many do not show such true branching. By finding it in L. scourfieldii, researchers can confirm the presence of the bacteria in this ecosystem.

What did the Rhynie Chert look like in the Early Devonian?

More than 400 million years ago, the Aberdeenshire landscape looked vastly different than it does today.

A large portion of Earth’s land area was located in the Southern Hemisphere. Located just south of the equator, Scotland experiences a tropical to subtropical climate.

Meanwhile, the Rainy Chert was an area of ​​flat, sandy land with shallow pools of fresh to brackish water. The area’s volcanic activity and hot springs mean it likely resembles modern Yellowstone National Park.

However, its biodiversity would have looked very different, as it did in the Early Devonian before forests and vertebrates became dominant on Earth.

Instead, the focus of life was on wet rocks near pools of water. These areas would have been covered with microbial mats consisting of bacteria, algae and fungi.

Because the soil at that time was not deep, the plants did not have complex root systems, so instead they grew on these microbial mats attached to tiny structures called roots.

At some point, the silica released from the hot springs settled around the organic matter, quickly preserving it in flint, a finely crystalline quartz. The exceptional preservation of these creatures makes the Rhynie Chert a globally important site for scientists.

“The Rhynie Chert is a special site because it is 400 million years old, and much of the environment from this time has been preserved,” says Christine.

“It’s the only site where you find traces of all living things together: plants, animals, fungi, bacteria and algae. And you can see the interactions between species that might be occurring.”