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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.
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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The significance of this study is that it provides evidence for the ability of bacteria to adapt and evolve in response to environmental changes, even under controlled lab conditions. This challenges the traditional view that evolution only occurs over long periods of time in nature.
The scientists used a process called "serial transfer", in which they repeatedly transferred the bacteria to a new environment with limited nutrients. This created a high-pressure situation, forcing the bacteria to adapt and evolve in order to survive.
Yes, the bacteria underwent significant physical changes, including changes in size, shape, and metabolism. This is evidence of the bacteria's ability to adapt and evolve in response to environmental pressures.
This study challenges the traditional view of evolution as a slow and gradual process, and suggests that bacteria may be capable of faster and more dramatic changes in response to environmental stressors. It also highlights the role of genetic variation and natural selection in driving evolutionary change.
By showing the ability of bacteria to adapt and evolve in a controlled lab setting, this study sheds light on the mechanisms behind the development of antibiotic resistance. It also emphasizes the importance of responsible antibiotic use and the need for continued research in this area.