Bacteria too can become extinct: Study

Bacteria go extinct at substantial rates, according to a study which contradicts the widely held notion that the microbes rarely die off because of their very large population.

The study, published in the journal Nature Ecology and Evolution, used massive DNA sequencing and big data analysis to create the first evolutionary tree encompassing a large fraction of Earth's bacteria over the past billion years.

"Bacteria rarely fossilise, so we know very little about how the microbial landscape has evolved over time," said Stilianos Louca, a researcher at the University of British Columbia (UBC) in Canada.

"Sequencing and math helped us fill in the bacterial family tree, map how they have diversified over time, and uncover their extinctions," Louca said.

The researchers estimate between 1.4 and 1.9 million bacterial lineages exist on Earth.

They were also able to determine how that number has changed over the last billion years - with 45,000 to 95,000 extinctions in the last million years alone.

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

Despite the frequent, steady extinction of individual species, the work shows that - overall - bacteria have been diversifying exponentially without interruption.

They have avoided the abrupt, planet-wide mass extinctions that have periodically occurred among plants and animals.

Louca suspects that competition between bacterial species drive the high rate of microbial extinctions, leaving them less prone to sudden mass, multi-species extinctions.

Past speciation and extinction events leave a complex trace in phylogenies - mathematical structures that encode the evolutionary relatedness between existing bacterial species.