Figure 7: Representation of PGSR phage sequences in the human gut metaproteome.

To further explore the functional profile of PGSR Bacteroidales-like phage, and their contribution to the human gut metaproteome, a shotgun metaproteome was generated from a human faecal microbiome and the resulting 177,729 mass spectra used to search custom databases of all putative proteins encoded PGSR phage, PGSR non-phage and VLP-derived contigs from human gut viral metagenomes¹¹. (a) Shows relative hit rates in the gut metaproteome, for amino-acid sequences originating in each data set used to query mass spectra (PGSR phage, PGSR non-phage, VLP-derived gut virome). Relative hit rates were calculated by normalizing the number of proteins from each data set detected in the gut metaproteome by the total number of ORFs in parental data sets (expressed as hits per total number of predicted proteins in each data set). Symbols above bars indicate statistically significant differences in relative hit rate with the data set of corresponding symbol colour (**P=0.01 or lower; ***P=0.001 or lower; χ²-test). Putative functions of identified proteins were based on COG searches (1e⁻² or lower; Supplementary Table S3). (b) Heat map shows relative abundance of sequences homologous to those detected in the gut metaproteome, within a broad cross section of bacterial and archaeal chromosomal sequences (n=1,821, PGSR non-phage), and phage sequences (711 phage genomes, PGSR phage sequences and assemblies of human gut viromes), expressed as hits per Mb DNA^48,49 (valid hits=minimum 35% identity over 30 aa or more, 1e⁻⁵ or lower). See Supplementary Table S1, Supplementary Data 3–6 for sources and details of sequences used.