The Surprising Individuality of Bacterial Clones

A mass of identical runners flooded the starting line. This was not your usual 5k. The scientists behind this contest will test both speed and the navigational ability of the competitors as they travel through a maze and choose the correct way on every intersection. Postdocs Mehdi Salek and Francesco Carrara stand by at the end of the course as they wait to identify each of the finishers. The participants, however, are not human. They are Escherichia coli bacteria. But what was the goal of the contest? It was individuality.

That there could be individual winners at all is a notion that has shaken the foundations of microbiology in recent years. Working in the lab of Roman Stocker at the Swiss Federal Institute of Technology Zurich (ETH Zurich), a team of microbiologists and engineers invented this unique endurance event. The cells at the starting line of Stocker’s microbial marathon were genetically identical, which implied, according to decades of biological dogma, that their resulting physiology and behavior should also be more or less the same, as long as all the cells experienced identical environmental conditions. At the DNA level, every E. coli cell had a roughly equal encoded ability to swim and steer through the course. A pack of cells that started the race at the same time would in theory all finish around the same time.
But that’s not what Salek and Carrara found. Instead, some bacteria raced through the maze substantially more quickly than others, largely because of varying aptitude for moving toward higher concentrations of food, a process called chemotaxis. What appeared to Salek and Carrara as a mass of indistinguishable cells at the beginning was actually a conglomerate of unique individuals.

Check out more of this study over at Quanta Magazine.

(Image Credit: CDC/Janice Haney Carr./ Wikimedia Commons)

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