Biodiversity and richness shifts of mucosa-associated gut microbiota with progression of colorectal cancer.

The host-associated gut microbiota is considered critical for the occurrence and progression of colorectal cancer (CRC); however, systematic evaluations of the changes in the biodiversity and richness of mucosa-associated gut microbiota with the development of CRC have been limited. Twenty-three paired samples from colorectal tumor sites and the surrounding non-tumor tissues were collected from stage I to IV CRC patients. The microbial compositions of the samples were analyzed by Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene. Gut bacterial alterations at the tumor sites and surrounding healthy tissue sites collected from the different stages of CRC patients were analyzed. No significant differences were observed in the overall microbial richness and biodiversity between the CRC tissue and surrounding non-CRC tissue samples, however, composition and community segregation of the gut microbiota with the progression of CRC were observed. A general increasing trend of Bacteroidetes, Firmicutes, and Fusobacteria and decreasing trend of Proteobacteria were observed at the phylum level with the development of CRC. Further analysis revealed that thirty-four taxa differed significantly with the progression of CRC. Conclusively, our findings provide a comprehensive view of the human mucosa-associated gut microbiota, in association with the different stages of CRC.