A mutant fitness assay identifies bacterial interactions in a model ocean hot spot

Significance Ecological interactions that occur between phycosphere-associated bacteria at the micron scale have the potential to influence a major fraction of annual carbon flux at the global scale. Despite the importance of microbial carbon flow, studying the ecology of these microenvironments remains challenging. Fitness measures of bacterial transposon mutants identified four primary classes of interactions among members of a model bacterial community provisioned by a cocultured diatom. This work advances our understanding of ecological associations in multispecies microbial environments.