Phylogenetic analysis of L. interrogans NulO biosynthetic enzymes. Amino acid sequence alignments of “aminotransferase,” “NulO synthase,” and “CMP-NulO synthetase,” enzymes were performed using Clustal W and phylogenetic trees were built using the Neighbor-Joining method. Campylobacter jejuni enzymes with characterized functions in bacterial neuraminic, legionaminic, and pseudaminic acid biosynthesis [14, 17–21] were compared to L. interrogans amino acid sequences encoded in the NulO biosynthetic gene cluster. Homologs of these enzymes from P. profundum strains 3TCK and SS9 were also included as they are know to synthesize legionamimic acid pseudaminic acids respectively . Homologous enzymes from other selected Leptospira genomes (L. noguchii str. 2006001870, L. biflexa serovar Patoc, L. santarosai str. 2000030832, L. borgpetersenii serovar Hardjo-bovis L550) were also included in the phylogenetic analysis.