Seminar title: Thriller | Abstract: “Thriller” is an appropriate metaphor for the mysterious mortality of fish and other animals in which thiamine deficiency was first recognized in the 1940s, yet did not receive substantial attention until fishery declines in the 1990s led to a focus on thiamine-degrading enzymes. More recently, the mysteries surrounding thiamine associated pathogenicity have expanded with the recognition of bacterial production of toxic thiamine analogues that interfere with essential biochemical pathways. Similar toxic analogues are produced by human pathogens responsible for three deadly ailments: post-infectious hydrocephalus, meliodosis, and botulism. Thiamine degrading enzymes are also produced by bacteria that control widespread pathogenic stramenopiles (previously considered to be fungi, though are quite distinct) responsible for many agricultural afflictions including Irish potato blight in the 1800s. Yep, very mysterious. But thrilling.