Evolution of New Traits in Microbes

Microbes evolve rapidly because of short generation times and large population sizes, making them ideal for studying evolution in the lab.

Natural selection acts on the existing allele variants in the population, making groups with helpful variants more abundant in shifting environments.

For example, in anaerobic conditions, Rhodobacter uses light to perform photosynthesis, using the pigments bacteriochlorophyll and carotenoids.

During prolonged darkness, Rhodobacter's pigments have little benefit, favoring pigment-lacking mutants in the population. But the wild type dominates once light returns.

Another example is the ongoing ‘Long-Term Evolution Experiment.' It was started in 1988 with 12 identical populations of E. coli growing in a glucose-limited environment.

Since then, this experiment has tracked more than 80,000 generations.

Over time, one E. coli population gained a rare mutation. And it allowed this population to metabolize citrate in oxygen-rich conditions.

This mutation provided access to a new nutrient source and a competitive advantage over their ancestors.