Flea-boe transmission is a recent evolutionary adaptation that distinguishes the deadly Yersinia pestis from its progenitor Y. pseudotuberculosis, a mild pathogen transmitted via the food-boe route. Y. pestis synthesizes biofilms in the flea gut, which is important for fleaboe transmission. Yersinia biofilms are bacterial colonies surrounded by extracellular matrix primarily containing a homopolymer of N-acetyl-D-glucosamine that are synthesized by a set of specific enzymes.Yersinia biofilm production is tightly regulated at both transcriptional and post-transcriptional levels. All the known structural genes responsible for biofilm production are harbored in both Y. pseudotuberculosis and Y.pestis, but Y. pestis has evolved changes in the regulation of biofilm development, thereby acquiring efficient arthropod-boe transmission.