Abstract: Objective： To assess whether the same biological conclusion, diagnostic or curative effects regarding microbial composition of irritable bowel syndrome (IBS) patients could be reached through different bioinformatics pipelines, we used two common bioinformatics pipelines (Uparse V2.0 and Mothur V1.39.5)to analyze the same fecal microbial 16S rRNA high-throughput sequencing data. Methods: The two pipelines were used to analyze the diversity and richness of fecal microbial 16S rRNA high-throughput sequencing data of 27 samples, including 9 healthy controls (HC group), 9 diarrhea IBS patients before (IBS group) and after Rifaximin treatment (IBStreatment, IBSt group). Analyses such as microbial diversity, principal coordinates analysis (PCoA), nonmetric multidimensional scaling (NMDS) and linear discriminant analysis effect size (LEfSe) were used to find out the microbial differences among HC group vs. IBS group and IBS group vs. IBSt group. Results: (1) Microbial composition comparison of the 27 samples in the two pipelines showed significant variations at both family and genera levels while no significant variations at phylum level; (2) There was no significant difference in the comparison of HC vs. IBS or IBS vs. IBSt (Uparse: HC vs. IBS, F=0.98,P=0.445;IBS vs. IBSt,F=0.47，P=0.926； Mothur:HC vs.IBS, F=0.82, P=0.646;IBS vs. IBSt, F=0.37, P=0.961). The Shannon index was significantly decreased in IBSt; (3) Both workshops distinguished the significantly enriched genera between HC and IBS groups. For example, Nitrosomonas and Paraprevotella increased while Pseudoalteromonadaceae and Anaerotruncus decreased in HC group through Uparse pipeline, nevertheless Roseburia 62 increased while Butyricicoccus and Moraxellaceae decreased in HC group through Mothur pipeline.Only Uparse pipeline could pick out significant genera between IBS and IBSt, such as Pseudobutyricibrio, Clostridiaceae 1 and Clostridiumsensustricto 1. Conclusion: There were taxonomic and phylogenetic diversity differences between the two pipelines, Mothur can get more taxonomic details because the count number of each taxonomic level is higher. Both pipelines could distinguish the significantly enriched genera between HC and IBS groups, but Uparse was more capable to identity the dif-ference between IBS and IBSt groups. To increase the reproducibility and reliability and to retain the consistency among similar studies, it is very important to consider the impact on different pipelines.

Key words: Irritable bowel syndrome, Bioinformatics, High-throughput sequencing