3D structure of the ΦcrAss001 virus particle. a, Molecular surface of the viral particle (virion), viewed from the outside. b, Cross-section through the virion. Proteins making up the capsid (protein shell) are shown in yellow and blue; cargo proteins are in purple; pink and pale-blue proteins on the capsid are head-fibre proteins; proteins making up the tail barrel are shown in different colours; and tail-fibre proteins are shown in grey. Credit: Bayfield, O. W. et al./Nature (CC BY 4.0).
CrAss-like phage (crassviruses) are a bacteriophage family representing the most abundant viruses in the human gut, discovered in 2014 by cross assembling reads in human fecal metagenomes.[1]In silicocomparative genomics and taxonomic analysis have found that crAss-like phages represent a highly abundant and diverse family of viruses.[2][3] CrAss-like phage were predicted to infect bacteria of the Bacteroidota phylum and the prediction was later confirmed when the first crAss-like phage (crAss001) was isolated on a Bacteroidota host (Bacteroides intestinalis) in 2018.[4] Crassviruses are podoviruses, possessing short non-contractile tails and icosahedral capsids. The first 3D structure of a crassvirus was determined by cryo-EM in 2023.[5][6] While the presence of crAss-like phage in the human gut is not yet associated with any specific health condition, they are generally associated with a healthy gut microbiome and likely impact significantly on the gut Bacteroidota.[3][2][7][8]