Beyond bacteria: Role of non-bacterial gut microbiota species in inflammatory bowel disease and colorectal cancer progression

Abstract

This letter emphasizes the need to expand discussions on gut microbiome’s role in inflammatory bowel disease (IBD) and colorectal cancer (CRC) by including the often-overlooked non-bacterial components of the human gut flora. It highlights how viral, fungal and archaeal inhabitants of the gut respond towards gut dys-biosis and contribute to disease progression. Viruses such as bacteriophages target certain bacterial species and modulate the immune system. Other viruses found associated include Epstein-Barr virus, human papillomavirus, John Cunningham virus, cytomegalovirus, and human herpes simplex virus type 6. Fungi such as Candida albicans and Malassezia contribute by forming tissue-invasive filaments and producing inflammatory cytokines, respectively. Archaea, mainly methanogens are also found altering the microbial fermentation pathways. This correspondence, thus underscores the significance of considering the pathological and physiological mechanisms of the entire spectrum of the gut microbiota to develop effective therapeutic interventions for both IBD and CRC.