In a combined study, researchers capture the act of organisms feasting upon each other with 1,900 million old fossils from the rocks around Lake Superior, Canada, reports Science Daily.
Researchers explain the act of micro-organisms feeding on other organisms that took place several million years ago, which also gives a hint of how the ancient Earth smelt like. The study, led by Dr. David Wacey of the University of Western Australia and Bergen University, Norway, and professor Martin Brasier of Oxford University, shows the ancient microbes feast on Gunflintia, a cyanobacterium-like fossil, as a "tasty morsel," in preference to other bacteria.
"What we call 'heterotrophy' is the same thing we do after dinner as the bacteria in our gut break down organic matter," said Brasier of Oxford University's Department of Earth Sciences, author of the paper. "Whilst there is chemical evidence suggesting that this mode of feeding dates back 3,500 million years, in this study for the first time we identify how it was happening and 'who was eating who.'"
"In fact we've all experienced modern bacteria feeding in this way as that's where that 'rotten egg' whiff of hydrogen sulfide comes from in a blocked drain," he said. "So, rather surprisingly, we can say that life on earth 1,900 million years ago would have smelled a lot like rotten eggs."
Researchers analyzed the 3-15 microns diameter microscopic fossils with the help of a new technique battery. They found that the fossil of one of the species that was believed to be the outer sheath of Gunflintia was more perforated after its death than the other species.
They also found that many of these tiny fossils had some places that were partially or entirely replaced with iron sulfide. Iron sulfide, commonly known as fool's gold, is a water waste product of heterotrophic sulfate-reducing bacteria. The Gunflintia fossils were also found to be carrying smaller rod-shaped and spherical bacteria that seemed to be in the process of feasting on their hosts.
According to an older geochemical analyses which was published in the journal Nature Geoscience in 2011, has shown that the "sulfur-based activities of bacteria can likely be traced back to 3,500 million years or so," Dr. Wacey said.
"Whilst the Gunflint fossils are only about half as old, they confirm that such bacteria were indeed flourishing by 1,900 million years ago. And that they were also highly particular about what they chose to eat," he said.
The findings of the study are published in the current week's journal of Proceedings of the National Academy of Sciences.
