Ancient Land Colonization: The Discover of 407-Million-Year-Old Cyanobacteria Fossils

Thursday - September 14 2023, 02:25 UTC - 1 year ago

Researchers have discovered the oldest species of Cyanobacteria known to have colonized land, Langiella scourfieldii in the Rhynie chert fossil site in Scotland’s Aberdeenshire. This species of Cyanobacteria displayed characteristic ‘true branching’, which helped confirmed its presence in the ecosystem. In addition, these Cyanobacteria are responsible for the Great Oxidation/Oxygenation Event which changed the Earth's atmosphere from carbon dioxide-rich to oxygen-rich.

Cyanobacteria, commonly known as blue-green algae, are the earliest known life forms on Earth. They are responsible for the Earth's transition from a carbon dioxide-rich atmosphere to the present relatively oxygen-rich atmosphere due to oxygenic photosynthesis. Ubiquitously found in ponds, lakes, water streams, rivers, and wetlands, they have played a significant role in shaping life. A team of researchers studying some of the earliest fossils has found the oldest species of Cyanobacteria known to have colonized land. The team studied fossils from thin samples collected from the famous Rhynie chert fossil site in Scotland’s Aberdeenshire.

407-million-year-old bacteria fossils .

"The Rhynie chert, our best preserved record of early terrestrial ecosystems, provides an opportunity to illuminate aspects of cyanobacterial diversity and ecology as plants began to radiate across the land surface," noted the researchers in the study. "Fortunately, we found new samples from the Rhynie Chert containing cyanobacteria that we could study in more detail using the confocal microscope." The team used light microscopy and super-resolution confocal laser scanning microscopy to study a new population of Rhynie cyanobacteria. Langiella scourfieldii, belonging to the Hapalosiphonaceae family, is a species of cyanobacteria that thrived among early land plants over 400 million years ago during the Early Devonian period.

Earliest evidence of land colonization .

One of the main characteristics of Langiella scourfieldii is the presence of ‘true branching.’ This occurs when individual bacteria grow alongside each other in a line, with some lines breaking off in different directions to create a branching structure, explained the researchers in the press release. Although Cyanobacteria is a fairly common component of the Rhynie Chert, many do not display this ‘true branching.’ By finding it in L. scourfieldii, researchers could confirm the bacteria's presence in this ecosystem.

"With the 3D reconstructions, we were able to see evidence of branching, which is a characteristic of Hapalosiphonacean cyanobacteria," said Dr. Christine Strullu-Derrien, a scientific associate at the Natural History Museum and lead author of the study. "This is exciting because it means that these are the earliest cyanobacteria of this type found on land," she added.

When the Earth was formed about 4.5 billion years ago, it had immensely different conditions than today. Its atmosphere was made up of carbon dioxide, methane, and water vapor. Cyanobacteria slowly released oxygen and changed the composition of the atmosphere to what it is today. This event is known as the Great Oxidation/Oxygenation Event, which occurred sometime between 2.4 – 2.1 billion years ago.

"Cyanobacteria in the Early Devonian played the same role that they do today," added Christine. "Some organisms use them for food, but they are also important for photosynthesis. We have learnt that they were already present when plants first began colonizing land and may have even competed with them for space." .

The study was published in the journal iScience.

Study abstract: Cyanobacterium Langiella scourfieldii, among the earliest evidence of life exploiting the land environment for nutrient acquisition, was discovered in the 407-million-year-old Rhynie chert. With its characteristic 3D morphotype, L. scourfieldii interacted with the earliest land plants and provides novel insights into the ecological balance of the Rhynie ecosystem.