A latest study on methane-forming archaea has found that a regulatory process, which switches-on photosynthesis in plants at daybreak, was present 2.5 billion years ago, long before oxygen became available.

In other words, ancient microbes already had an important part of photosynthesis ready before oxygen came into the picture. The study was conducted by researchers at Virginia Tech and University of California, Berkeley.

Archaea (domain Archaea), are simple, single-celled organisms that can live in extreme environments. They are separate from prokaryotes (  such as bacteria) and eukaryotes ( such as plants and animals).

Methane-forming archaea are also known as methanogens and live in oxygen-deprived areas. These bacteria are important for the carbon-cycle. When plants and animals die, their remains get trapped in areas that have low levels of oxygen. These microbes then help convert the biomass into methane, which is then used by other organisms.

In the present study, researchers looked at Methanocaldococcus jannaschii, which lives in conditions that mimic ancient earth, such as hydrothermal vents or volcanoes.

Researchers found that the microbe had protein thioredoxin, which helped the organism repair damage caused by oxygen. Thioredoxin plays an important role in photosynthesis.

According to the team, it is possible that thioredoxin-based metabolic regulation helped anaerobes ( living without oxygen) survive tough conditions on earth before the arrival of oxygen.

Methanogens are crucial for life on earth and are present everywhere, including the guts of cattle and sheep, where they help digestion of feed. Research has shown that the ancient domain of archaea is also present in the human digestive system.

"By looking at this one mechanism that was not previously studied, we will be able to develop new basic information that potentially has broad impact on contemporary issues ranging from climate change to obesity," said Biswarup Mukhopadhyay, an associate professor of biochemistry at the Virginia Tech College of Agriculture and Life Sciences and senior author of the study, according to a news release.

The study is published in the journal Proceedings of the National Academy of Sciences.