Fig. 2

Pan-core-genome analysis of 15 closed Vibrio alginolyticus strains. a Number of gene clusters for pan (dashed line) and core genome (solid line) resulting from the sequential addition of genomes. The curve shows mean values of multiple iterations (> 100) where genomes were randomly added and the pan- and core-genome was calculated successively for all 15 steps (left: All 15 V. alginolyticus strains) and nine steps (right: Kiel-Fjord V. alginolyticus only). b Gene presence (dark blue) -absence (light blue) matrix showing the distribution of core and accessory genes for each of the 15 V. alginolyticus genomes. Each row corresponds to one strain, each column represents an orthologous gene family. Numbers on the right (#C) correspond to number of gene clusters per genome. The red square indicates the core-region specific for the Kiel isolates, the six mega-plasmids are indicated by white pL letters. c Bayesian phylogenetic tree of all 15 isolates based on the core-genome alignment