Human gut microbiota shows high inter-subject variations, but the actual spatial distribution and co-occurrence patterns of gut mucosa microbiota that occur within a healthy human instestinal tract remain poorly understood. In this study, we illustrated a model of this mucosa bacterial communities' biogeography, based on the largest data set so far, obtained via 454-pyrosequencing of bacterial 16S rDNAs associated with 77 matched biopsy tissue samples taken from terminal ileum, ileocecal valve, ascending colon, transverse colon, descending colon, sigmoid colon and rectum of 11 healthy adult subjects. Borrowing from macro-ecology, we used both Taylor's power law analysis and phylogeny-based beta-diversity metrics to uncover a highly heterogeneous distribution pattern of mucosa microbial inhabitants along the length of the intestinal tract. We then developed a spatial dispersion model with an R-squared value greater than 0.950 to map out the gut mucosa-associated flora's non-linear spatial distribution pattern for 51.60% of the 188 most abundant gut bacterial species. Furthermore, spatial co-occurring network analysis of mucosa microbial inhabitants together with occupancy (that is habitat generalists, specialists and opportunist) analyses implies that ecological relationships (both oppositional and symbiotic) between mucosa microbial inhabitants may be important contributors to the observed spatial heterogeneity of mucosa microbiota along the human intestine and may even potentially be associated with mutual cooperation within and functional stability of the gut ecosystem.

Gut microbiota dysbiosis may be associated with the presence of MHE in cirrhotic patients, in particular with ammonia-increasing phenotype in MHE. Gut ammonia-increasing bacteria S. salivarius might be expected to be a potential biomarker of ammonia-lowering therapies in cirrhotic patients with MHE.

BackgroundThe aim of this study is to expand existing knowledge about the CRC-associated microbiome among Han Chinese, and to further discover the variation pattern of the human CRC microbiome across all population.FindingsUsing pyrosequencing-based molecular monitoring of bacterial 16S rRNA gene from eight tumor/normal tissue pairs of eight Chinese CRC patients, we analyzed and characterized the basic features of the CRC-associated microbiome. Firstly, we discovered an increasing diversity among tumor-associated bacterial communities. Secondly, in 50% of Chinese CRC patients, we found a significant increase of Roseburia (P = 0.017), and a concurrent decrease of both Microbacterium (P = 0.009) and Anoxybacillus (P = 0.009) in tumor tissue.ConclusionsWe discovered a novel CRC microbiome pattern in Chinese. Both the over-represented Roseburia bacteria at tumor sites and the over-represented Microbacterium and Anoxybacillus bacteria away from tumor sites were both closely related in Chinese CRC patients. Across several populations reported in this study and previously, we observed both common and distinctive patterns of human CRC microbiome’s association with a high-risk of CRC.