However, when we analyzed the microbiome data of individual A from the V4F-V6R dataset and the data of individual C from the V6F-V6R dataset, the Firmicutes phylum was identified for individual C, and Proteobacteria was no longer identified as a biomarker for individual A (Figure 4c). Surprisingly, when we analyzed the microbiome data for individual A from the V6F-V6R dataset and the data for individual C from the

V4F-V6R dataset, no biomarkers were identified for the two groups (not shown in Figure 4, as no biomarkers were identified). A similar situation occurred when analyzing find more the data from individuals B and D, as there were no biomarkers identified when the V6F-V6R dataset was used for individual B and the V4F-V6R dataset was used for individual D (Additional file 1: Figure S2). Taken together, these results suggest that while similar biomarkers GSK872 in vivo can be obtained even when different primer sets and sequencing 17DMAG clinical trial batches are used, meta-analysis should be performed cautiously when using data obtained from different sources. Figure 4 LEfSe comparison of microbial communities between individuals

A and C with different data sources. (a) Individual A and C are both from V46 library. (b) Individual A and C are both from V6 library. (c) Individual A is from V46 library and Individual C is from V6 library. Conclusions For the purposes of meta-analysis, PCA using both the binary and abundance-weighted Jaccard distance D-malate dehydrogenase is reliable, and Shannon diversity index is also relatively stable across different studies. However, the richness estimators, especially those depending primarily on rare tags (e.g., Chao and ACE) are significantly affected by the experimental procedures unique to individual studies. The community structure, especially the relative abundance, also varies significantly between different datasets. Biomarkers between different groups are comparable between multiple experiments if the input data

for the LEfSe analysis is obtained from a single experiment, but meta-analyses using combined datasets should be performed cautiously. In the present study, we only take into account primer bias and sequencing quality, and their effect on microbiota analyses from combined studies, variations in the experimental procedures of different laboratories could also affect the meta-analyses. Additional studies verifying the PCR conditions, particularly the enzyme system, DNA extraction, DNA storage effect, etc., are needed in future. Acknowledgements This work was supported by the National Natural Science Foundation of China (NSFC 31270152, 31322003), the COMRA project (DY125-15-R-01), the Program for New Century Excellent Talents in University (NCET-11-0921), the Guangdong Natural Science Foundation (No.