FIG. 6.

Comparison of predicted EPS gene clusters in bifidobacterial genomes. The EPS biosynthetic gene cluster in Lactobacillus rhamnosus ATCC 9595 was obtained from the work of Peant et al. (228). All genes were categorized according to their potential functions, as follows: A, chain-length determination; B, Wzx flippase for EPS synthesis; C, glycosyltransferase; D, glucose transferase; E, rhamnosyltransferase; F, polysaccharide polymerase/oligosaccharide repeat unit polymerase; G, polysaccharide pyruvyl transferase; H, dTDP-glucose pyrophosphorylase; I, dTDP-4-dehydrorhamnose-3,5-epimerase; J, dTDP-d-glucose-4,6-dehydratase; K, dTDP-4-keto-l-rhamnose reductase; I/K, fused protein of I and K; and L, priming glycosyltransferase/galactosyltransferase/UDP-galactose phosphotransferase. Genes with red numbers are bifidobacterium-specific genes predicted to be involved in EPS biosynthesis, as follows: 1, extracellular exopolygalacturonase; 2, UDP-glucose/GDP-mannose dehydrogenase; 3, UDP-N-acetylglucosamine/glucuronate/galacturonate-4-epimerase; 4, β-1,4-galactosyltransferase enhancer; and 5, UDP-galactopyranose mutase. Gray arrows indicate genes involved in dTDP-rhamnose precursor biosynthesis. Sky blue arrows indicate hypothetical genes. The red boxes indicate IS mobile elements. MIC, mobile integrase cassette consisting of three contiguous integrase genes (green) sandwiched by two IS3 mobile elements (161). The genome locations of the gene clusters are indicated in kilobases.