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Do bacteria ever go extinct? Absolute!



Microbial mat near a hot spring in Iceland. Credit: Stilianos Louca, University of British Columbia

Bacteria emit substantial rates, though they seem to avoid the mass extinction that has struck greater forms of life on Earth, according to new research from the University of British Columbia (UBC), Caltech and Lawrence Berkeley National Laboratory. This finding contradicts the widespread scientific thesis that microbial taxa rarely die due to their very large populations.

The study, published today in Nature Ecology and Evolution, used massive DNA sequencing and big data analysis to create the first evolutionary pedigree. It covers a large part of Earth's bacteria in the past billions of years.

"Bacteria rarely fossilize, so we know very little about how the microbial landscape has developed over time," says Stilianos Louca, researcher at Biodiversity Research at UBC Center, who led the study. "Sequencing and math helped us capture the bacterial lineage, track its diversification over time, and expose it to extinction." Although modern bacterial diversity is undoubtedly high, it is only a small part of the diversity that evolution has brought about the earth. History

Louca and colleagues estimate that today on Earth, between 1

.4 and 1 , 9 million bacterial lines exist. They were also able to determine how that number has changed over the last billion years – in the last million years alone, with 45,000 to 95,000 extinctions.

"Although modern bacterial diversity is undoubtedly high, it is only a tiny snapshot of the diversity that evolution has created over Earth's history," says Louca.

Despite the frequent, steady extermination of individual species, the work shows that bacteria generally diversify exponentially without interruption. And they have avoided the abrupt, planet-wide mass extinctions that have occurred periodically between plants and animals. Louca suggests that competition between bacterial species drives the high rate of microbial death and makes them less susceptible to sudden mass extinction of several species.

Former speciation and extinction events leave a complex trace in phylogenies – mathematical structures that encode the evolutionary relationship between existing bacterial species

"This study would not have been possible 10 years ago," says Michael Doebeli , UBC mathematician and zoologist and senior author on the paper. "Today's availability of extensive sequencing data and powerful computational resources enabled us to perform the complex mathematical analysis."

The discovery that high-rate bacterial taxa are becoming extinct also has far-reaching implications for paleobiology, as it suggests the microbial fossils found by the researchers may not be closely related to modern species – even though they resemble them, but rather Kaden represent without representatives.

Next, Louca and his colleagues want to determine how the physiological properties of bacteria will evolve over time, and whether their ecological diversity has also increased similarly to their taxonomic diversity. If true, that would mean that even old and relatively simple organisms like bacteria still have the potential to find new ways to survive.

This article has been republished by materials from the University of British Columbia. Note: Material may have been edited for length and content. For more information, please contact the cited source.

Reference
Bacterial diversification by geological time. Stilianos Louca, Patrick M. Shih, Matthew W. Pennell, Woodward W. Fischer, Laura Wegener Parfrey and Michael Doebeli. Nature Ecology & Evolution (2018), https://doi.org/10.1038/s41559-018-0625-0.


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