Drug effects on <i>Enterococcus faecalis </i>biofilms: growth, topology, and population dynamics

Extensive research over decades has led to a relatively mature understanding of the molecular mechanisms of antibiotic resistance, but developing drugs to outpace the resistance threat is a major challenge. To complement this molecular approach, researchers have recently shifted their focus to longer length scales, where ecological and evolutionary dynamics of bacterial communities highlight new approaches for slowing resistance with currently available drugs. In this talk, I will discuss our ongoing work to understand how antibiotics shape, and are reshaped by, the spatial architecture of bacterial biofilms at the single-cell level. Biofilms dynamics differ significantly from that of well-stirred populations in liquid ("planktonic") communities. By combining confocal microscopy with simple mathematical models I will show how antibiotics impact not only the composition of the biofilm--specifically, the balance of susceptible and resistant cells in the community-- but also the way those cells are arranged in space. Our results suggest that in spatially structured populations, which may more accurately reflect natural bacterial communities, the selection of resistance is not a simple result of homogeneous selections but depends critically on the spatial arrangement of cells.