Lisa H. Willis

Highlights • DNA barcodes allow tracking of bacterial strain-level dynamics in the mouse gut • Mutations in motility and metabolic genes are reproducibly selected for within days • A population-genetics model predicts a bacterial migration rate of >10% per day • Ciprofloxacin treatment decreases strain diversity and stimulates transmission Summary Due to limitations on high-resolution strain tracking, selection dynamics during gut microbiota colonization and transmission between hosts remain...

Highlights • A general model links cell size-homeostasis statistics to cell-cycle mechanisms • Many cell-cycle mechanisms that appear plausible cannot maintain cell size • Mechanisms that enact adder behavior may also result in highly robust size control • Cell-cycle features can play unintuitive roles in size-homeostasis behaviors Summary High-throughput imaging has led to an explosion of observations about cell-size homeostasis across the kingdoms of life.

Highlights • The majority of Bacillus subtilis cells die upon oxygen depletion • Surfactin production depolarizes cells to maintain viability upon oxygen depletion • Surfactin promotes growth in early stationary phase by enhancing oxygen diffusion • The autolytic enzyme LytC and surfactin mediate lysis upon oxygen depletion Summary The presence or absence of oxygen in the environment is a strong effector of cellular metabolism and physiology.