Slow but steady wins the drug race

Bacteria that survive antibiotic assaults fall into two groups: resistant mutants; and the more mysterious persistent cells. Persisters, a known entity since 1944, survive the intial burst of antibiotics but unlike mutants may succumb to later treatments. Nathalie Balaban (now at Hebrew University, Jerusalem, Israel), Stanislas Leibler (Rockefeller University, New York, NY), and colleagues now find that persisters are a constant presence in the population—a slow-growing minority that acts as a reserve population in case of chemical attack.

The alternative explanations for persisters are legion. They might be completely dormant, or normal cells caught in a protected part of the cell cycle when the antibiotic arrives, or a state induced in response to antibiotic treatment. Balaban and colleagues looked at the behavior of single cells immobilized in a microfluidic device and saw that...