Figure 6:Multidimensional scaling (MDS) plots of human intestinal bacterial community composition based on pyrosequencing after 48 h exposure to Left Panel: 0 (Control), 25 (Low), 100 (Medium) and 200 (High) mg/L silver nanoparticles (AgNP), and Right Panel: 0 (Control), 2.5 (Low), 10 (Medium) and 20 (High) mg/L polyvinylpyrrolidone (PVP) concentrations, respectively. Arrows indicate the distance of the AgNP- treatment groups from the control with no Ag.