Background:Irritable bowel syndrome(IBS)is reported associated with the alteration of gut microbial composition termed as dysbiosis.However,the pathogenic mechanism of IBS remains unclear,while the studies of Chinese individuals are scarce.This study aimed to understand the concept of dysbiosis among patients with Chinese diarrhea-predominant IBS(IBS-D),as a degree of variance between the gut microbiomes of IBS-D population and that of a healthy population.Methods:The patients with IBS-D were recruited(assessed according to the Rome III criteria,by IBS symptom severity score)from the Outpatient Department of Gastroenterology of Peking University Third Hosp让al,and volunteers as healthy controls(HCs)were enrolled,during 2013.The 16S rRNA sequences were extracted from fecal samples.Ribosomal database project resources,basic local alignment search tool,and SparCC software were used to obtain the phylotype composition of samples and the internal interactions of the microbial community.Herein,the non-parametric test,Wilcoxon rank-sum test was carried out to find the statistical significance between HC and IBS-D groups.All the P values were adjusted to q values to decrease the error rate.Results:The study characterized the gut microbiomes of Chinese patients with IBS-D,and demonstrated that the dysbiosis could be characterized as directed alteration of the microbiome composition leading to greater disparity between relative abundance of two phyla,Bacteroidetes(Z=4.77,q=1.59×10^-5)and Firmicutes(Z=-3.87,q=5.83×10^-4).Moreover,it indicated that the IBS symptom features were associated with the dysbiosis of whole gut microbiome,instead of one or several certain genera even they were dominating.Two genera,Bacteroides and Lachnospiracea incertae sedis,were identified as the core genera,meanwhile,the non-core genera contribute to a larger pan-microbiome of the gut microbiome.Furthermore,the dysbiosis in patients with IBS-D was associated with a reduction of network complexity of the interacted microbial community(HC us.IB
Exploring the mechanisms of maintaining microbial community structure is important to understand biofilm development or microbiota dysbiosis. In this paper, we propose a functional gene-based composition prediction(FCP) model to predict the population structure composition within a microbial community. The model predicts the community composition well in both a low-complexity community as acid mine drainage(AMD) microbiota, and a complex community as human gut microbiota. Furthermore, we define community structure shaping(CSS) genes as functional genes crucial for shaping the microbial community. We have identified CSS genes in AMD and human gut microbiota samples with FCP model and find that CSS genes change with the conditions. Compared to essential genes for microbes, CSS genes are significantly enriched in the genes involved in mobile genetic elements, cell motility, and defense mechanisms, indicating that the functions of CSS genes are focused on communication and strategies in response to the environment factors. We further find that it is the minority, rather than the majority, which contributes to maintaining community structure. Compared to health control samples, we find that some functional genes associated with metabolism of amino acids, nucleotides, and lipopolysaccharide are more likely to be CSS genes in the disease group. CSS genes may help us to understand critical cellular processes and be useful in seeking addable gene circuitries to maintain artificial self-sustainable communities. Our study suggests that functional genes are important to the assembly of microbial communities.
Using high-throughput sequencing on metagenome to analyze marine microbial community, it is one of current main issues in the field of environmental microbe research. In this paper, we conducted the functional analysis on seven samples of metagenomic data from different depth seawater in Hawaii. The results of gene prediction and function annotation indicate that there are large amounts of potential novel genes of which functions remain unknown at present. Based on the gene annotation, codon usage bias is studied on ribosomal protein-related genes and shows an evident influence by the marine extreme environment. Furthermore, focusing on the marine environmental differences such as light intensity, dissolved oxygen, temperature and pressure among various depths, comparative analysis is carried out on related genes and metabolic pathways. Thus, the understanding as well as new insights into the correlation between marine environment and microbes are proposed at molecular level. Therefore, the studies herein afford a clue to reveal the special living strategies of microbial community from sea surface to deep sea.
