Bacteria Make Major Evolutionary Shift in the Lab

[Moridin]

Bacteria Make Major Evolutionary Shift in the Lab

A major evolutionary innovation has unfurled right in front of researchers' eyes. It's the first time evolution has been caught in the act of making such a rare and complex new trait.

And because the species in question is a bacterium, scientists have been able to replay history to show how this evolutionary novelty grew from the accumulation of unpredictable, chance events.

Twenty years ago, evolutionary biologist Richard Lenski of Michigan State University in East Lansing, US, took a single Escherichia coli bacterium and used its descendants to found 12 laboratory populations.

The 12 have been growing ever since, gradually accumulating mutations and evolving for more than 44,000 generations, while Lenski watches what happens.

This is pretty cool.

 

[Adeimantus]

But sometime around the 31,500th generation, something dramatic happened in just one of the populations – the bacteria suddenly acquired the ability to metabolise citrate, a second nutrient in their culture medium that E. coli normally cannot use.

Indeed, the inability to use citrate is one of the traits by which bacteriologists distinguish E. coli from other species. The citrate-using mutants increased in population size and diversity.

"It's the most profound change we have seen during the experiment. This was clearly something quite different for them, and it's outside what was normally considered the bounds of E. coli as a species, which makes it especially interesting," says Lenski.
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Neat!

 

[Moonbear]

It's nice this has been so well documented. It's a common problem with cell cultures of mammalian origin too. I was recently at a conference where several people all using the "same" cell line (from the same original source) were discussing issues of problems replicating findings across different labs. As they were discussing the characteristics of the cell line, it dawned on them that they no longer have the same cell line. It has independently mutated in each of the labs to display different characteristics. It's something people working with cell cultures need to be aware of and need to check every so often to make sure that what they are studying hasn't changed to something they didn't intend to be studying.