Diversity Of Symbiotic Gut Microbes And Their Correlation With Human Metabolic Phenotype

The human endogenous gut microflora is an immensely diverse ecosystem and also an essential metabolic "organ" of the huaman being. In mammals, the microbiota influences many aspects of host biology including dietary calorific bioavailability, epithelial development and immune status as well as drug metabolism and toxicity.However, the characterization of the gut microbiota has been hindered by the refractory cultivation of the most species using methods available now. With the development of the molecular microbiology techniques, more and more genes of the microbiota have been sequenced. But such studies have been limited by little or no function correlation with the sequenced gene fragments, and little attention given to potential variation associated with time, diet, race and sex. In addition, molecular mechanisms of the interaction between microbiota (microbiome) variation and human physiology have not been adequately described, nor have the key microbiota contributors.We examined 7, 255 16S ribosomal RNA gene sequences from fecesof a 7-membered healthy Chinese family subjects, in order to improve our understanding of gut microbial diversity of the Chinese individuals. A majority of the bacterial sequences corresponded to uncultivated species and novel microorganisms. According to the 99% sequence similarity, the sequences were grouped into 476 OTUs and affiliated into 6 major phyla following Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Verrucomicrobia, and Fusobacteria which were congruent with reports by some study groups such as Eckburg and Gill group. Characterization of human symbiotic microbes is the first step in elucidating its role in health and disease.In order to study potential variation associated with environment, diet, and sex between different people, we explored the Chinese family data with the data obtained from science journal of two recent similar studies conducted on USA volunteers. The total 11,656 sequences were grouped into 854 Phylotypes. Through ∫-Libshuff analysis, we found significant inter-subject variability of community composition even among the family members. Through bioinformatics, ecological statistical and multivariate analysis, we discovered the Chinese family studied shared a similar division-level phylogenetic landscape with the American individuals. In contrast, the Chinese and American gut microbiomes were clearly different at species-level composition as shown by the principalcoordinate analysis. Through PCA and PLS-DA we also firstly reported sex-related difference in the global composition and structure of gut microbiome of the combination of the family members and the American individuals.Many studies found that the microbial community composition and function often shift together. Nicholson Group have found that there are significant differences in the observed metabolic phenotypes of Chinese and USA populations and our study discovered the significant different gut microbiomes between 7 Chinese and 5 USA individuals. So is there any co-variation between the differences of gut micobiota and metabolic phenotypes? Utilizing this paradigm, the mechanisms underlying the symbiotic gut microbes potentially modulate the human metabolic phenotypes and functional key strains could be unraveled through metabolic phenotypes monitoring and dissecting the microbial communities.Hence, after this preliminary overall structural survey, we analyzed time-related stability of the global structure of the microbiome using PCR-DGGE and the urinary metabolite profiles by ~1H NMR over a month for the Chinese family samples. We found the covariation between DGGE fingerprinting patterns reflecting microbiomic structure and hostmetabolic phenotype as defined by NMR urine profiles using Orthogonal Projection to Latent Structures (OPLS) multivariately model and the sex-related differences in both gut microbiota and host metabolism in the Chinese family. We firstly reported that Symbiotic gut microbes could modulate human metabolic phenotypes.The closest relative isolates of the key functional species that potentially correlated with the human metabolic phenotypes were B.thetaiotaomicron, B.uniformis, B.coprocola, Pseudobutyrivibrio ruminis, bacterium mpn-isolate group 25, Ruminococcus bromii, Faecalibacterium prausnitzii 1-88, Subdoligranulum variable BI-114, Bifidobacterium pseudocatenula. The key band variables, which were responsible for the sex separation, were Eubacterium eligens, Ruminococcus obeum, Klebsiella pneumoniae, Sutterella stercoricanis, Bacteroides thetaiotaomicron, Ruminococcus bromii et. al.. And we also characterized the associated metabolites by 2D-NMR and many of them are well-known metabolites produced by gut bacteria or co-metabolites with the host such as phenylacetylglutamine, 4-cresol sulphate, 4-hydroxyphenylacetate etc..Here we examined 7,255 prokaryotic 16S rRNA gene sequences from a 7-membered Chinese family and proposed a new strategy to find the"key" functional microbes of the diverse gut flora. The theory of symbiotic gut microbes modulate human metabolic phenotypes gives a new cline or direction for human health care. And this new strategy also could be applied to explore the co-metabolic mechanism between microbiome and host metabolism and mechanism or new biomarkers of their contribution to human health and diseases. And this discovery also has supplied a new example for Gordon's discovery-the association between gut flora and obesity.