Fig. 2

a Comparison of the alpha diversity estimates between NGS platforms for the mock bacterial communities. Box and whisker plot (median, interquartile range and min/maximum values) of the comparison of the Shannon Diversity index (y-axis) values obtained for the mock bacterial community at genus level classification for the two NGS platforms (x-axis) (n = 4) using Wilcoxon-rank sum test showed no significant difference between the two platforms (w = 10, p = 0.69). b Comparison of the alpha diversity estimates at genus level distribution for the primers and the NGS platforms for the mock bacterial community (MiSeq – blue column and Roche454 –red column –values indicated are Shannon diversity index in each category where n = 1). Mixed V3-4 and Mixed V1-3: Shannon diversity index for the two NGS platforms for the mock bacterial community with simulated human DNA contamination amplified using primer pair spanning V3-V4 and V1-V3 hypervariable regions of the 16S rRNA gene. Pure V3-4 and Pure V1-3: Shannon diversity index for the two NGS platforms for the mock bacterial community amplified using primer pair spanning V3-V4 and V1-V3 hypervariable regions of the 16S rRNA gene