Local Adaptation of Bacteriophages to Their Bacterial Hosts in Soil

Microbes are incredibly abundant and diverse and are key to ecosystem functioning, yet rela-tively little is known about the ecological and evolutionary mechanisms that shape their distribu-tions. Bacteriophages, viral parasites that lyse their bacterial hosts, exert intense and spatially varying selection pressures on bacteria and vice versa. We measured local adaptation of bacteria and their associated phages in a centimeter-scale soil population. We first demonstrate that a large proportion of bacteria is sensitive to locally occurring phages. We then show that sympatric phages (isolated from the same 2-gram soil samples as the bacteria) are more infective than are phages from samples some distance away. This study demonstrates the importance of biotic in-teractions for the small-scale spatial structuring of microbial genetic diversity in soil..