Distribution and relative abundance of plasmid encoded functions in the human gut microbiome. A) Relative abundance of pTRACA22 ORFs, expressed as hits/Mb, in the combined human gut metagenomes of 15 individuals [9, 10] compared to the combined murine gut metagenome , Sargasso sea , and soil metagenomes . Symbols above bars indicate significant differences between combined human metagenomes and each non-human metagenome (P = 0.01 or less), and colours correspond to each non-human metagenome: Orange = Significant difference between human and murine metagenomes; Blue = Significant difference between human and marine metagenomes; Brown = significant difference between human and soil metagenomes. B) Distribution of amino acid sequences homologous to ORFs encoded by pTRACA10 and pTRACA22 in 15 individual human gut metagenomes. Bars indicate the number of human metagenomes in which amino acid sequences homologous to each plasmid encoded ORF were detected. Colours within bars indicate the overall % identity of the top hits (based on bit score) in each metagenome to the corresponding plasmid ORF. Letters adjacent to bars indicate human metagenomes in which sequences homologous to plasmid ORFs were identified: A) Human7, B) Human8 ; C) InA, D) InB, E) InD, F) InE, G) InM, H) InR, I) F2-V, J) F2-W, K) F2-X, L) F2-Y, M) F1-S, N) F1-T, O) F1-U . * indicates metagenomic sequences that correspond to those represented in Figure 2 and Table 1. C) Relative abundance (as hits/Mb) of the pTRACA22 RelBE TA module in human gut, murine gut and environmental metagenomes, compared to relative abundance of MazEF, ParDE and HigBA TA modules. The observed differences between human and non-human metagenomes were explored using the χ2 distribution. Symbols above bars indicate approximate significance of differences between combined human metagenomes and each non-human metagenomes (P = 0.01 or less), as in Fig 1a.