Blood type and the microbiome- untangling a complex relationship with lessons from pathogens

[Display omitted] •A historical perspective on associations between ABO blood type and bacteria.•Mechanisms that drive relationships between host blood type and commensal and pathogenic bacteria.•Review of conflicting evidence for an influence of host blood type on the intestinal microbiome.•How this knowledge may inform the development of microbiome-targeted intervention strategies. The complex communities of microbes that constitute the human microbiome are influenced by host and environmental factors. Here, we address how a fundamental aspect of human biology, blood type, contributes to shaping this microscopic ecosystem. Although this question remains largely unexplored, we glean insights from decades of work describing relationships between pathogens and blood type. The bacterial strategies, molecular mechanisms, and host responses that shaped those relationships may parallel those that characterize how blood type and commensals interact. Understanding these nuanced interactions will expand our capacity to analyze and manipulate the human microbiome.