Species-level verification of Phascolarctobacterium association to colorectal cancer

Background and aims: We have previously demonstrated an association between increased abundance of Phascolarctobacterium and colorectal cancer (CRC) and adenomas in two independent Norwegian cohorts. Here we seek to verify our previous findings using new cohorts and methods. In addition, we characterize lifestyle and sex-specificity, the functional potential of the Phascolarctobacterium species and their interaction with other microbial species. Methods: We analyze Phascolarctobacterium with 16S rRNA sequencing, shotgun metagenome sequencing and species-specific qPCR, using 2350 samples from three Norwegian cohorts - CRCAhus, NORCCAP and CRCbiome - and a large publicly available dataset, Curatedmetagenomedata. Using metagenome assembled genomes from the CRCbiome study we explore genomic characteristics and functional potential of the Phascolarctobacterium pangenome. Results: Three species of Phascolarctobacterium associated with adenoma/CRC were consistently detected by qPCR and sequencing. Positive associations with adenomas/CRC were verified for P. succinatutens and negative associations were shown for P. faecium and adenoma in Curatedmetagenomedata. Men show higher prevalence of P. succinatutens across cohorts. Co-occurrence among Phascolarctobacterium species was low (<6%). Each of the three species show distinct microbial composition and form distinct correlation networks with other bacterial taxa, although Dialister invisus was negatively correlated to all investigated Phascolarctobacterium species. Pangenome analyses showed P. succinatutens to be enriched for genes related to porphyrin metabolism and degradation of complex carbohydrates, whereas glycoside hydrolase enzyme 3 was specific to P. faecium. Conclusion: We have verified that P. succinatutens is increased in adenoma and CRC and this species should therefore be recognised among the most important CRC-associated bacteria.