Flagellar Oncogenicity in the Hypocomplement–Tumour Holobiont: A Five-Prediction Hypothesis Paper on Bacterial Flagella as Effectors of Virus-Driven and Coinfection-Driven Carcinogenesis

The 2020–2025 literature establishes that bacterial flagella function as multi-functional virulence organelles beyond motility, that intratumoural microbiota form a coherent microbial ecology, and that chronic viral infection and coinfection reshape this ecology in predictable ways. However, the mechanistic relationship between (i) bacterial flagellar biology, (ii) complement evasion, (iii) tumour-microbiome dominance, and (iv) viral and coinfection-driven oncogenesis has not been unified. This hypothesis paper proposes that flagellated bacteria constitute the principal effectors of viral and coinfection-driven oncogenesis within the fastidious–complement–tumour holobiont niche. Five predictions are formally stated (P1–P5), and a sixth extended hypothesis (H6) is advanced regarding flagellar oncogenicity specifically when viruses and coinfections meet. Each prediction is testable with currently available biobanked material in the case of P1–P3, with published xenograft models in P4, and with prospective cohort design in P5. The H6 extension generates a research agenda for the next decade of immuno-oncology-microbiome research.