The natural diversity of E. coli transporter-dependent capsules

Serotyping of bacteria using genomic information (in silico serotyping) has increasingly replaced serology. However, the E. coli capsule serotyping system has been largely abandoned since the 1990s, leaving gaps in our knowledge of capsule genetics, diversity, distribution, and epidemiology. To address this, we established a definitive genotype-serotype map for 35 serologically identified and structurally characterized transporter-dependent capsules. We then surveyed >37,000 E. coli genomes, cataloging 85 transporter-dependent capsule types (K-types), including 55 novel ones. We leveraged this catalog to develop an in silico serotyping tool, kTYPr, and applied it to curated sets of >25,000 E. coli genomes and metagenome-assembled genomes spanning diverse environmental and clinical sources. We found novel K-types enriched in under-sampled environments and associated with E. coli disease. This research expands our understanding of E. coli surface structures, supporting efforts for precision targeting with phage therapy or vaccines.