Biomarker Characteristics of Gut Bacteria from a Chinese Cohort of Colorectal Cancer, Colorectal Adenoma and Postoperative Patients

Colorectal cancer (CRC) accounts for the third-highest burden of morbidity among malignant tumors worldwide. Previous studies have investigated changes in gut bacteria occurring during the progression of colorectal adenomas (CRA) to overt CRC, highlighting the importance of the gut microbiome to carcinogenesis. However, only a few studies have focused on gut bacterial characteristics across the spectrum from CRC development through to beyond the treatment process. This study used 16S rRNA amplicon sequencing to compare the composition of gut bacteria from 68 fecal samples from 15 patients with CRC, 19 patients with CRA, 19 postoperative CRC patients (PP) and 15 healthy controls (HC). Our analysis showed no changes in alpha diversity between the different samples, although beta diversity was significantly different among the HC, CRC, CAC, and PP groups. Bacteroidetes, Firmicutes, Proteobacteria, and Actinobacteria were the dominant gut bacterial phyla in the four groups with several potential biomarker bacteria identified in the CRC and CRA groups at the phyla, order, class, and genus levels. In particular, the abundance of Actinomyces urogenitali, Bacteroides plebeius, Bacterium enrichment, Parabacteroides johnsonii, Fusobacterium varium and Bifidobacterium breve were dramatically different between groups, and associated with cancer or cancer-predisposing CRA lesions. Additional PICRUSt analysis identified 24 KEGG orthologs associated with the gut bacterial communities from the four groups, including general function prediction, carbohydrate transport and metabolism, transcription, amino acid transport and metabolism, cell wall/membrane/envelope biogenesis. Further large-scale prospective studies are needed to identify the functional consequences of the altered bacterial composition on the metabolism and CRC tumorigenesis in the host.