Leptospira gene clusters predict nonulosonic acid biosynthesis A. The sequenced genome of L. interrogans serovar Copenhageni L1-130 (top) and L. interrogans serovar Lai strain 56601 (bottom) encode a cluster of genes with predicted activities in the synthesis of sialic acids (N-acetylneuraminic acid) or related molecules. B. PCR of sialic acid cluster genes shows DNA amplification in pathogenic Leptospira species. Integrity of DNA was confirmed by amplification of the 16 S rRNA gene. C. Southern blots probed for the NeuA-2 region of the gene cluster using a DIG-labeled oligonucleotide. Genomic DNAs from the following bacteria were probed as described in materials and methods: 1) S. enterica, 2) L. interrogans serovar Lai strain 55601, 3) L. interrogans serovar Copenhageni strain L1-130, 4) L. biflexa serovar Patoc, 5) L. licerasiae (rat isolate CEH 008), 6) L. licerasiae isolate MMD4847), 7) L. interrogans serovar Icterohaemorrhagiae (isolate MMD 3731), 8) L. fainei serovar Hurstbridge, 9) S. enterica.