||P.207 right column bottom paragraph: "The concentration per gram of faeces varies in humans from 10^7 to 10^9 colony-forming units (cfu) [refs 11, 12, 13] and is much lower in domestic animals, averaging between 10^4 and 10^6 cfu [ref 13] (Table 1)." P.214 left column 2nd paragraph: "The prevalence of these virulence factor genes is variable among commensal populations. On a global scale, the human microbiota is characterized by a higher prevalence of virulence genes than the microbiota in other organisms [ref 85] (Table 1). In animals, the presence of virulence genes increases with body mass, which reflects the gut complexity of larger animal [ref 85]. Hence, virulence factors and their change in prevalence among hosts may reflect some local adaptation to commensal habitats rather than virulence per se."