Microbial growth dynamics and human disease

How do human-associated microbial communities contribute to health and disease? To answer this, scientists have been exploring changes in the gut microbiota between individuals, and even across generations and continents (1, 2). Large genome sequence data sets are producing tally sheets of bacteria in time and space throughout disease courses (3, 4). One challenge has been to determine the metabolic state of these microbial communities to identify bacteria that are responding to a perturbation and/or driving disease pathogenesis (5, 6). On page 1101 of this issue, Korem et al. (7) explore metagenomic DNA sequence data sets to estimate growth rates (metabolic states) of bacterial taxa in a microbial community.