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Fig. 5. Altered gastric microbiota in the three stomach microhabitats influenced by Helicobacter pylori infection (HPI). HPI influenced the 2NBDG indices of gastric microbiota in different stomach microhabitats such as Shannon (a), Simpson (b), Heip evenness (c), and the richness indices such as Chao 1 (d), PD whole tree (e) and observed species (f). Data are presented as mean ± standard deviation. Unpaired t-tests (two-tailed) were used to analyse variation between HP+ and HP− groups in the three stomach microhabitats. Plots of principal coordinate analysis (PCoA) of the gastric microbiota influenced by HPI in normal microhabitats (g), peritumoral microhabitats (h) and tumoral microhabitats (i) based on the unweighted UniFrac metric. Rarefaction analysis of the gastric microbiota from HP+ and HP− groups in three stomach microhabitats (j). Taxonomic differences between the gastric microbiota of HP+ and HP− groups in the three microhabitats at the phylum level (k). The different relative abundance of HP in histopathological HP+ and HP− groups in the three microhabitats (l). Data are presented as mean ± standard deviation. Mann-Whitney U tests were used to analyse variation between the HP+ and HP− groups in the three stomach microhabitats.
Fig. 6. PiCRUSt-based gastric microbiome study in the three different stomach microhabitats. The different bacterial functions in the three stomach microhabitats were evaluated between each other based on two-sided Welch's t-test (a). Comparisons among the three stomach microhabitats for each COG functional category shown by percentage (b). The Benjamini-Hochberg method was used for multiple testing correction based on the false discovery rate (FDR) by STAMP.
required to explore the roles and mechanisms of these differential bac-terial species among different GC tumoral environments in GC develop-ment. Furthermore, evaluation of the interactions between GC microbiota and the gastric immune system, and specific microbial func-tions in cancer microenvironments might prove valuable.
In summary, we completed a large-scale analysis of GC tumors using high-throughput sequencing techniques and found that the diversity and composition of the gastric microbiota were significantly altered in
different stomach microhabitats. In contrast to previous studies that considered the stomach as a whole, our study observed that the stom-ach microhabitats determined the overall structure and composition of the gastric microbiota, regardless of different GC stage and type. Inter-estingly, the carcinogenic pathogen H. pylori was significantly decreased in tumoral sites, which simplified the network of bacterial interactions in the gastric microbiota. The altered composition of the gastric micro-biota in the three stomach microhabitats may be associated with its
role in gastric carcinogenesis. However, the role of the different bacteria of the gastric microbiota in specific microhabitats remains unclear. Further studies are required to determine the gastric bacteria in tumoral microhabitats and host interactions in the process of gastric carcinogenesis.
The authors thank all of the participants who recruited patients in this study. We also thank Prof. Emad El-Omar and Dr. Fatima EL-Assaad for the valuable evaluation.
Availability of data and materials
All data generated or analyzed during this study are included in this published article and its supplementary information files.
XSL and ZXL conceived and designed the experiments. XSL, XL, FJ, YM, YWC, FPL, CXY, LJL and ZXL performed the experiments. XSL, LS, and ZXL analyzed the data. XSL, LS and ZXL wrote the paper and edited the manuscript. The final manuscript was read and approved by all authors.
Conflicts of interest
The authors declare no conflicts of interest.
Consent for publication
We have obtained consents to publish this paper from all the partic-ipants of this study.
Ethics approval and consent to participate
All research conformed to the Helsinki Declaration and was approved by the Ethics Committee of the First Affiliated Hospital, School of Medicine, Zhejiang University (China) and were implemented in ac-cordance with the approved guidelines. Informed written consent was obtained from each of the patients before enrollment.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
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