A new study by researchers at the Tokyo Life Sciences Institute shows that ancient bacterial communities lived and thrived on iron and a trace amount of oxygen.
And according to Official statement Released from the Tokyo Institute of Life Sciences, so-called “iron-oxidizing bacteria” in hot springs suggest that ancient microbes used iron and oxygen, not sunlight, as their primary source of energy.
This happened as the planet transitioned from a low-oxygen to a high-oxygen atmosphere about 2.3 billion years ago, forming ecosystems that recycled elements such as carbon, nitrogen and sulfur.
The results of this study are expected to help scientists understand the microbial ecosystem during a crucial period in Earth’s history, and may also help in the search for life on other planets.
The great oxygenation event
In the past, billions of years ago, the Earth was not as it is today, with its blue and green colors, as it is home to forests, coral reefs, mountain ranges, deserts, and millions of species of animal and plant organisms, with the exception of a small amount of tiny microbial organisms. Oxygen was almost non-existent in those ancient times, as oxygen levels in the early Earth were about a million times lower than what we know today.
But then, everything changed in what is known as the Great Oxidation Event about 2.3 billion years ago, in which Earth saw the emergence of atmospheric oxygen and allowed life as we know it to flourish.
Scientists believe that this event was due to the emergence of photosynthetic microbes capable of producing oxygen, specifically cyanobacteria that began using sunlight to break down water and carbon dioxide through the process of photosynthesis, releasing oxygen as a byproduct.
Initially, this oxygen reacted immediately with iron and minerals in the oceans and Earth’s crust, forming the thick layers of rusty iron oxides we see today in ancient rocks.
As millions of years passed, these minerals became saturated, and oxygen gradually began to accumulate in the atmosphere.
This change completely changed the chemistry of the Earth, ending the era of anaerobic organisms that cannot tolerate oxygen, and paving the way for the existence of more complex organisms capable of using oxygen for respiration, a process that produces much more energy than anaerobic fermentation.
As is known, the current atmosphere consists of about 78% nitrogen and 21% oxygen, with traces of other gases such as methane and carbon dioxide, which may have played a larger role before the advent of oxygen.
How did ancient microbes adapt to oxygen?
The team studied five hot springs in Japan that are rich in diverse water compositions. These five springs (one in Tokyo, and two each in Akita and Aomori Prefectures) are naturally rich in iron(II), which is rare in our oxygen-rich world today, because iron(II) quickly reacts with oxygen and turns into the insoluble form of iron(II), according to the study Published in the journal Microbes and Environment.
But in these springs, the water still contains high levels of iron(II), low levels of oxygen, and a near-neutral pH, conditions thought to be similar to parts of early Earth’s oceans.
In four of the five hot springs, the research team discovered that aerophilic, iron-oxidizing bacteria were the dominant microbes.
According to a Tokyo Life Sciences Institute statement, hot springs in Japan, rich in iron, provide a unique natural laboratory for studying microbial metabolism under conditions similar to those of early Earth during the late Archean to early Proterozoic transition, which was marked by the Great Oxidation Event.
Thus, such springs help us understand how primitive microbial ecosystems formed before plants and animals appeared, or provided atmospheric oxygen in large quantities, says Sean McGlynn, who supervised the study.
Analysis results
Using metagenomic analysis, the team collected more than 200 high-quality microbial genomes and used them to analyze in detail the functions of microbes in the community. The same microbes, which linked iron and oxygen metabolism, converted a toxic compound into an energy source, and helped maintain conditions that allowed oxygen-sensitive anaerobic bacteria to survive.
These microbial communities also carried out basic biological processes, such as the carbon and nitrogen cycle, and the researchers also found evidence of a partial sulfur cycle, as they identified genes involved in sulfide oxidation and sulfate assimilation.
Since hot springs contain only trace amounts of sulfur compounds, this was a surprising discovery. The researchers suggest that this may indicate a “mysterious” sulfur cycle, in which microbes recycle sulfur in complex ways that are not yet fully understood
“Despite differences in geochemical and microbial composition across sites, our results show that in the presence of ferrous iron and limited oxygen, communities of microscopic iron oxidizers, oxygenic photosynthetic organisms, and anaerobes constantly coexist and maintain remarkably similar and complete biochemical cycles,” says Fatima Li Hao, a graduate student at the Tokyo Life Sciences Institute, who conducted the study, in statements obtained by Al Jazeera Net.
“The research signals a shift in our understanding of early ecosystems, showing that microbes may have exploited energy from the oxidation of iron and oxygen produced by early photosynthetic organisms,” Hao adds.
The post Hot springs in Japan reveal the secrets of the oldest forms of life on Earth sciences appeared first on Veritas News.
