Colorectal cancer (CRC) is among the most prevalent forms of cancer (1). CRC has markedly complex risk factors involving genetic predisposition, diet, and gut microbiota (2), but the link between diet and CRC is complex and evidence in the literature is conflicting (3). The objective of this study was to evaluate the effect of protein- and fibre-rich diets on the composition and function of defined communities derived from healthy donor faecal samples and CRC patient tumour biopsies. In the current work, an in vitro model of the human distal gut was used to continuously culture colonic bacterial communities in protein- and fibre-enriched media representative of ileal outputs. The effect of diet on three healthy donor- and three CRC patient-derived communities was investigated based on the link between protein-rich diets and CRC risk, the association between fibre-rich diets and gut health, and the proteolytic fermentative metabolism of several bacterial species linked to CRC. In addition to diet having a direct effect on overall human health and on the gut microbiome, the effect of diet on gut communities is hypothesised to influence colonic health with respect to CRC. Gut bacterial products have been linked to health and CRC risk, onset, and progression (4). There is a need to understand the influence of diet on gut bacterial community structure and function, and whether diet can promote pro-cancerous activity in both the gut communities of healthy individuals and CRC patients. By disentangling and characterizing these complex interactions between host, bacteria, and diet, we can improve the understanding of the role of gut bacterial communities in CRC onset and progression.
 

Bacteria and viruses are associated with numerous cancer types and have been attributed with 20% of cancers worldwide. Most notably the associations between Helicobacter pylori with stomach cancer and Human Papilloma Virus with numerous cancer types including cervical cancer. Here we report on investigations into the microbiome of the urogenital tract using different modalities, including anaerobic culture, 16S ribosomal sequencing, RNA-sequencing and metagenomics analysis of tumour whole genome sequencing data. We report on the generation of the Anaerobic Bacterial Biomarker Set (ABBS): a list of bacterial genera (Fenollaria, Peptoniphilus, Anaerococcus, Porphyromonas, Fusobacterium, Ezakiella). When at least one of these bacteria was identified in urine or primary prostate tumour samples, patients demonstrated a tendency to develop more aggressive disease (meta-analysis hazard ratio: 2.60, 95% confidence interval: 1.39-4.85; p=0.003; cox regression). Future work lies in unravelling the nature of this association.