CrAssphage
crAssphage (cross-assembly phage) is a bacteriophage (virus that infects bacteria), discovered in 2014 by computational analysis of human faecal metagenomes and later isolated for the first time in 2018. It infects the human gut symbiont Bacteroides crAssphage. CrAssphage has a circular DNA genome 102 kbp in size and contains 80 predicted open reading frames, and the sequence is commonly found in human faecal samples. At the time of its discovery, the virus was predicted to infect bacteria of the phylum Bacteroidota that are common in the intestinal tract of many animals including humans. Based on analysis of metagenomics  data, crAssphage sequences have been identified in about half of all sampled humans. The virus was named after the crAss (cross-assembly) software that was used to find the viral genome. CrAssphage is possibly the first organism to be named after a computer program for promotional purposes. CrAss-phage does not correlate strongly with variables relating to diet, lifestyle, or health, and does not appear to be strongly involved in human health or disease. The virus may outperform indicator bacteria as a marker for human faecal contamination. The RNA polymerase of crAssphage is homologous to proteins catalyzing RNA interference in  animals and humans, rather than to their own RNA polymerase. crAss-like phages. In silico comparative genomics and taxonomic analysis have found that crAss-like phages represent a highly abundant family of viruses. Based on a screen of related sequences in public nucleotide databases and phylogenetic analysis, it was concluded that crAssphage may be part of an extensive bacteriophage group (within "Podoviridae", order "Caudovirales") with diverse members that are found in a range of environments including human gut and faeces, termite gut, terrestrial/groundwater environments, soda lake (hypersaline brine), marine sediment, and plant root environments. CrAss-like phages are estimated  to comprise about 10 genera. Since then, so-called gubaphages have been identified as the second most common phage group in the human intestinal flora. The characteristics of the gubaphages are reminiscent of those of "p-crAssphage".