Nonulosonic acid (NulO) biosynthesis in bacteria is directed by <i>nab</i> gene clusters that can lead to neuraminic, legionaminic or pseudaminic acids. Analysis of the gene content from a set mainly composed of <i>Aliivibrio salmonicida</i> and <i>Moritella viscosa</i> strains reveals the existence of several unique nab clusters, for which the NulO products were predicted. This prediction method ...