Involved in the assembly of a N-linked pentasaccharide that decorates the S-layer glycoprotein and flagellins. Involved in the biosynthesis of the hexuronic acids found at both positions 2 and 3 of the pentasaccharide. H2O + 2 NAD(+) + UDP-alpha-D-glucose = 3 H(+) + 2 NADH + UDP-alpha-D-glucuronate Activity improves as salinity decreases. Nucleotide-sugar biosynthesis; UDP-alpha-D-glucuronate biosynthesis; UDP-alpha-D-glucuronate from UDP-alpha-D-glucose: step 1/1. Cell surface structure biogenesis; S-layer biogenesis. Mutants exhibit defective or limited motility. Belongs to the UDP-glucose/GDP-mannose dehydrogenase family.