Metagenome Analysis Of Intestinal Bacteria In Patients With Inflammatory Bowel Disease And Colorectal Cancer

Objective: There is a symbiotic relationship between intestinal microorganisms and mammals.Intestinal microorganisms have the ability to affect different physiological aspects.In recent years,some studies have emphasized the serious imbalance of microorganisms in intestinal diseases.Several reports suggesting that the intestinal microbiome plays a key role in the development of inflammatory bowel disease(IBD)or colorectal cancer(CRC),but the changes of intestinal bacteria in healthy people,patients with IBD and CRC are not fully explained.The study aimed to investigate changes of intestinal bacteria in healthy subjects,patients with IBD,and patients with CRC.Methods: We collected data from the European Nucleotide Archive(ENA)on healthy people and patients with colorectal cancer with the study accession number PRJEB6070,PRJEB7774,PRJEB27928,PRJEB12449,and PRJEB10878,we collected IBD patient data from the Integrated Human Microbiome Project(i HMP)from the Human Microbiome Project(HMP).We performed metagenome-wide association studies(MWAS)on the fecal samples from 290 healthy subjects,512 IBD patients,and 285 CRC patients.We used the metagenomics dataset to study bacterial community structure,relative abundance,functional prediction,differentially abundant bacteria,and co-occurrence networks.Results: Our results showed that IBD had low intestinal bacterial diversity and CRC had high intestinal bacterial diversity compared to healthy subjects.At the phylum level,the relative abundance of Firmicutes in IBD decreased significantly,while the relative abundance of Bacteroidetes increased significantly.Compared with healthy people and CRC,the main difference of intestinal bacteria in IBD patients was Bacteroidetes.Compared with healthy people and IBD,the main difference of intestinal bacteria in CRC patients were Fusobacteria,Verrucomicrobia and Proteobacteria.At the genus level,the relative abundance of Bacteroides in IBD was higher than in healthy people and CRC.At the level of species,the highest abundance bacteria of healthy people,IBD and CRC was Faecalibacterium prausnitzii.Eubacterium rectale was the biggest difference between healthy people and IBD or CRC.Compared with healthy people and CRC,Bacteroides uniformis was the highest relative abundance in IBD.Compared with CRC and healthy people,the most significant difference in patients with IBD was Akkermansia muciniphila.The main differences in the functional composition of intestinal bacteria in healthy people,IBD and CRC patients were L-homoserine and L-methionine biosynthesis,5-aminoimidazole ribonucleotide biosynthesis II,L-methionine biosynthesis I,and Superpathway of L-lysine,L-threonine and L-methionine biosynthesis I.The results of stratified showed that the abundance of Firmicutes,Bacteroidetes and Actinobacteria involved in metabolic pathways has significantly changed.Besides,the association network of intestinal bacteria in healthy people,IBD,and CRC patients has also changed.Conclusion: The diversity of intestinal bacteria in patients with IBD is low,there are large differences between patients with IBD,and the bacteria are very unstable.The results of bacterial stratification analysis showed that the metabolic pathways of Firmicutes,Bacteroides and Actinobacteria had changed significantly.Finally,the association network of intestinal bacteria in patients with inflammatory bowel disease and colorectal cancer has changed.