we next checked if multiple samples harbored CRISPR spacers targeting each of the 991 phage contigs we detected, regardless of samples. Indeed, a majority of phages (72%) were targeted by spacers found in bacteria from multiple individuals, with the maximum number of individuals targeting a single phage reaching 43 (supplemental data set S6). the observation that gut microbiota across individuals possess spacers targeting some of the same phages may reflect a combination of shared bacterial strain ancestry and ongoing pressure maintaining or shaping gut bacterial CRISPR arrays to respond to these shared phages.