While past research has pointed to bacteria potentially adapting to keep pace with changing environments, the new study says that even bacteria can be unsuccessful at keeping the pace when conditions change suddenly or frequently.
The research team, led by the University of Bristol, looked at 2,458 ancient bacterial genomes recovered from the past 250 million years of Earth history. By tracking extinction rates over time, the team found that bacteria could go extinct at a very high rate at certain times—rates that were comparable to those seen in larger lifeforms like plants and animals.
The study's lead author, Dr. Tom Williams, a Royal Society Dorothy Hodgkin Fellow in Bristol's School of Earth Sciences, said: "Bacteria have a reputation as the ultimate survivors. But our research complicates that idea by revealing they have experienced many waves of extinction in the past. In some cases, bacteria may be pushed to the brink because they are struggling to adapt to new environments, opening the door for other species to replace them."
While a great many microbes survive for extremely long periods of time—"some of the ones that we found might be the longest-lived organisms in Earth history"—others can endure for as short as a few tens of thousands of years before extinction, the authors found.
What Drives Extinctions?
The results point to a variety of causes behind the bacterial extinctions, including:
Climate change: Shifts in temperature and other climate conditions can change what bacteria can thrive. The researchers write that even small changes in climate can have outsized effects on many types of bacteria.
Competition with other microbes: Different species of bacteria compete with each other for food and resources. When those resources become scarce, some species may die off.
Predation: Even single-celled organisms are not safe from being preyed upon by larger organisms. Tiny predators such as viruses and bacteriophage (viruses that infect bacteria) can wipe out large numbers of bacteria.
"Understanding the extinction of bacteria is important for understanding the fate of ecosystems as a whole, as well as how bacteria influence the evolution of large-scale Earth systems such as the biosphere and atmosphere," Williams said. "Bacteria interact directly and indirectly with plants and animals, and changes in bacterial communities—particularly those involved in nutrient cycling—may ultimately affect the habitability of our planet for all organisms, including ourselves."
The research team says their findings can help scientists better understand how bacterial communities will respond to future environmental changes, such as those caused by human activity.
"There is a risk that we are driving current-day microbial communities towards extinction, potentially with major consequences for the ecosystems in which they live and the services they provide us," Williams said.
