Metagenomic Evaluation of the Highly Abundant Human Gut Bacteriophage CrAssphage for Source Tracking of Human Fecal Pollution

Recently, a highly abundant and widespread bacteriophage, named crAssphage, was identified in the human gut. Here, 86 publically available metagenomes were surveyed to determine the presence and abundance of crAssphage in various environments and to identify its utility for source tracking of human fecal pollution. CrAssphage was found to be highly abundant in sewage and biosolids from the United States and Europe and less abundant in sewage from Asia and Africa. CrAssphage was not definitively identified in other samples, including animal fecal material, with the exception of bat guano. Approximately half of mapped reads in the bat guano metagenome clustered to orf00045 in the phage genome, suggesting homology to a closely related phage. These results indicate the potential utility of a crAssphage-based marker for source tracking of human fecal waste and highlight the utility of metagenomic approaches for initial identification and verification of fecal source tracking markers.