Abstract
Summary The O‐antigen is a highly diverse structure expressed on the outer surface of Gram‐negative bacteria. The products responsible for O‐antigen synthesis are encoded in the wbe region, which exhibits extensive genetic diversity. While heterogeneous O‐antigens are observed within Vibrio species, characterization of these structures has been devoted almost exclusively to pathogens. Here, we investigate O‐antigen diversity among coastal marine Vibrio splendidus ‐like isolates. The wbe region was first identified and characterized using the sequenced genomes of strains LGP32, 12B01 and Med222. These regions were genetically diverse, reflective of their expressed O‐antigen. Additional isolates from physically distinct habitats in Plum Island Estuary (MA, USA), including within animal hosts and on suspended particles, were further characterized based on multilocus sequence analysis (MLSA) and O‐antigen profiles. Results showed serotype diversity within an ecological setting. Among 48 isolates which were identical in three MLSA genes, 41 showed gpm genetic diversity, a gene closely linked to the wbe locus, and at least 12 expressed different O‐antigen profiles further suggesting wbe genetic diversity. Our results demonstrate O‐antigen hyper‐variability among these environmental strains and suggest that frequent lateral gene transfer generates wbe extensive diversity among V. splendidus and its close relatives.