Persisters: Specialized Cells Responsible for Biofilm Tolerance to Antimicrobial Agents
The study of biofilms is a rapidly expanding field of microbiology. Biofilm research encompasses studies of many topics including multispecies communities, cell-cell signaling, virulence, industrial fouling, and bioremediation, to name a few. Yet it is fair to say that the field was propelled to its present prominence due to a singular feature that unites all biofilms-namely their dramatic tolerance to antimicrobial agents. This tolerance is responsible for recalcitrant human infections, accounting for ~60% of all infectious diseases in the West (1). A large number of empirical studies documenting biofilm tolerance have been published in the past two decades. At the same time, there has been a paucity of molecular biology research into the mechanism of tolerance. This may seem surprising, given the prominence of the problem, and our generally good understanding of various mechanisms of antibiotic resistance (2). The reason for this reluctance to tackle the main question of the biofilm field may have stemmed from the suggestion that the problem does not really exist. Biofilms are slow growing, while antibiotics act best against rapidly dividing cells. The action of most β-lactams, for example, depends stringently upon rapid growth (3).