A new study has revealed the technique that two major groups of microbes use to survive below the Earth’s surface. These microbes are examples of ancient, early life on Earth. A publication in Frontiers in Microbiology first indicated that these microbes survive based on symbiotic relationships, however, new research indicates that these groups can survive independently using an ancient form of energy production.
“These microbes, which belong to the groups Patescibacteria and DPANN, are really special, really exciting examples of the early evolution of life,” said Ramunas Stepanauskas, an author of the paper. “They may be remnants of ancient forms of life that had been hiding and thriving in the Earth’s subsurface for billions of years.”
Ramunas Stepanauskas is also a senior research scientist at Bigelow Laboratory for Ocean Sciences. He and his team used bioinformatics and advanced molecular techniques to analyze thousands of microbial genomes. Upon reading their genetic code, it was revealed that these microbes don’t have the ability to traditionally “breathe” to synthesize ATP.
Instead, these groups of microbes rely on an ancient form of energy production by fermentation. This type of energy production isn’t new – even human muscles undergo fermentation after heavy exercise. However, these are just supplementary sources of energy. These groups of microbes use fermentation as the only source of energy, a technique that is ancient and thought to have been extinct.
“Our findings indicate that Patescibacteria and DPANN are ancient forms of life that may have never learned how to breathe,” Stepanauskas said. “These two major branches of the evolutionary tree of life constitute a large portion of the total microbial diversity on the planet—and yet they lack some capabilities that are typically expected in every form of life.”
Fermentation is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. This means that these organisms can even survive in the presence of little to no oxygen, deep beneath the Earth’s surface. It was previously speculated by scientists that the groups of microbes, Patescibacteria and DPANN, must exist only in symbiotic relationships due to their simple genetic nature.
However, there was no evidence found that most relationships are symbiotic. In fact, it was found that most of these microbes live independently using fermentation as a source of energy. “Dependence on other organisms is a feature of life,” said Jacob Beam, a former postdoctoral researcher at Bigelow Laboratory and the lead author of this study. “There are no absolutes in biology, and our research shows that microbes can vary along the spectrum of interdependencies.”
This research was conducted in collaboration with Bigelow Laboratory Bioinformatics Scientist Julie Brown, Research Scientist Nicole Poulton, former Postdoctoral Research Scientists Eric Becraft and Oliver Bezuidt, and Research Experience for Undergraduates intern Kayla Clark. An international team of scientists also contributed to field, lab, and computational analysis work.
The most interesting takeaway from this research is the wider spectrum where the findings can be applied. Since it was found that life such as Patescibacteria and DPANN can survive with very little energy, it would be safe to assume that these conditions would also need to be present for life on other planets such as Mars to survive.
“This project would not have been possible without the collaboration of this diverse group of scientists collecting samples around the world and uniting their expertise,” Beam said. “Through the collaboration of a global group of scientists working together, we know more about the inner workings of these microbes that form a major fraction of the total biodiversity on our planet.”
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