...sometime around the 31,500th generation, something dramatic happened in just one of the [twelve] populations – the bacteria suddenly acquired the ability to metabolise citrate, a second nutrient in their culture medium that E. coli normally cannot use...Something, he concluded, must have happened around generation 20,000 that laid the groundwork...Lenski and his colleagues are now working to identify just what that earlier change was, and how it made the Cit+ mutation possible more than 10,000 generations later.

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 outside what was normally considered the bounds of E. coli as a species, which makes it especially interesting," says Lenski.

Lenski's experiment is also yet another poke in the eye for anti-evolutionists, notes Jerry Coyne, an evolutionary biologist at the University of Chicago. "The thing I like most is it says you can get these complex traits evolving by a combination of unlikely events," he says. "That's just what creationists say can't happen.".

http://www.newscientist.com/article/dn14094-bacteria-make-major-evolutionary

"Time is what prevents everything from happening at once" - John Wheeler