I can’t think of a great analogy in human terms, so (for me, at least) a comparison is difficult. E. coli has the enzymatic capacity for anaerobic citrate utilization, but it typically only does it under anaerobic conditions.When biochemically testing for E. coli, aerobic citrate utilization is a common test. The citrate in the culture medium was added only as a chelating agent, without the expectation for citrate utilization genes to alter. However, one particular sample in the LTEE started utilizing citrate under aerobic conditions. A lot of YEC and ID yawn at it because “it is still E. coli!”, but others have at least asked the question “Is it really still E. coli if a fundamental identification test no longer indicates that it is E. coli?”
The biochemical capabilities of this particular strain didn’t change dramatically, but the expression of the involved genes did. It is certainly fascinating (particularly the main mutation that allowed this), and although I consider it a pretty big deal, it isn’t as dramatic as developing an entirely new set of genes allowing metabolism of a completely new food source (the article is probably a bit misleading).