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Background: The importance of microbiome in the progression and development of colorectal cancer (CRC) has been discussed in the last decade. Like colon bacteria, other intestinal microorganisms, including archaea, could also be involved in the CRC progression, so it's important to work out the archaeal microbiome (archaeome) composition among CRC patients. Objectives: The aim of this study was to determine the archaeome composition of CRC and healthy controls based on age and gender. Methods: Total bacterial DNA was extracted from 30 biopsy samples (17 CRC and 13 healthy controls). Archaeome communities were profiled by 16S rRNA high throughput sequencing, then compared to clinicopathological features, including CRC patients’ gender and age. Results: In the CRC patients, archaeal methanogens including Methanobrevibacter (86%) and Methanomassiliicoccus (8%) were overrepresented at the genus level. In contrast in the healthy controls, only two genera of haloarchaea including Natronococcus (58%) and Haloterrigena (42%) were presented. The results showed that the number of archaeal genera in men is higher than women in both the CRC and healthy controls. moreover, our results showed that the most genera of archaea are present in the CRC-32-50 group, six archaeal genera. The differential abundance taxa analysis results showed significant differences between healthy controls and CRC patients (P ≤ 0.05). Conclusions: The high abundance of methanogens in the colon archaeome of CRC patients compared to healthy controls suggests that methanogens may be involved in CRC development.

Background: Colorectal cancer (CRC) is the third most common malignant tumor worldwide. Emerging evidence suggests that dysbiosis of the colon microbiome may be involved in CRC development. Objectives: The present study aimed to compare the composition and diversity of the colon microbiome by high-throughput 16S ribosomal RNA (rRNA) sequencing between CRC patients and healthy controls. Microbiome composition and diversity were also examined based on gender. Methods: The colon microbiome richness and diversity of samples from 17 CRC patients and 13 healthy controls were analyzed by 16S rRNA sequencing. Alpha and beta diversity were calculated to determine the differences in colon microbiome diversity. Results: Alpha and beta diversity showed significant differences between the CRC and healthy control groups regarding the microbiome. Our results showed that CRC samples had the highest richness and diversity. The total number (P ≤ 0.01), phylogenetic diversity (P ≤ 0.01), Chao1 (P ≤ 0.01), Shannon (P ≤ 0.05), and Simpson (P ≤ 0.01) indices were significantly higher in the CRC group than in the healthy control group. In addition, the comparison between females and males showed that the microbiome diversity was higher in the CRC female (CRC-F) group than in other groups. Prevotella, Fusobacterium, Akkermansia, Leptotrichia, Streptococcus, and Parabacteroides were more commonly observed in the CRC group, while Bacteroides, Enterobacteriaceae (unknown genus), Ruminococcus, and Campylobacter were more commonly observed in the healthy control group. Conclusions: This study showed differences between the CRC and healthy control groups regarding the diversity and composition of the colon microbiome, suggesting a contribution of the microbiome in the development and progression of CRC.