Biologists have deduced that metabolisms based on munching or belching methane evolved early on, but don’t know exactly when, says Barbara Cavalazzi, a geobiologist at University of Bologna in Italy. Previous research has found indirect evidence for methane-cycling microbes in the chemistry of fluid-filled pockets of ancient rocks from around 3.5 billion years ago. But that work didn’t find the actual microbes. With this fossil analysis, “what we find, basically, is evidence of about the same age. But this is a cellular remain — it’s the organism,” Cavalazzi says.
The newly identified fossil threads have a carbon-based shell. That shell is different structurally from the preserved interior, suggesting a cell envelope enclosing the cells’ insides, the authors write. And the team found relatively high nickel concentrations in the filaments. The concentrations were similar to levels found in modern methane-makers, suggesting the fossils’ metal may come from nickel-containing enzymes in the microbes.
The newly identified fossil threads have a carbon-based shell. That shell is different structurally from the preserved interior, suggesting a cell envelope enclosing the cells’ insides, the authors write. And the team found relatively high nickel concentrations in the filaments. The concentrations were similar to levels found in modern methane-makers, suggesting the fossils’ metal may come from nickel-containing enzymes in the microbes.
