Schematic representation of the metabolism of sialic acid among Bacteria. Summary of varied pathways of sialic acid utilization in Bacteria. The catabolic pathway of sialic acid involves several steps beginning with NanA. Highlighted in orange is the donor-scavenging synthesis of sialic acid. Highlighted in pink is the de novo pathway for the synthesis of sialic acid. For a more comprehensive review of sialic acid utilization see refs. 1 and 29. NanH, Neuraminidase; Neu5Ac, N-acetylneuraminic acid, sialic acid; T, sialic acid transporter; NanA, N-acetylneuraminic acid lyase; ManNAc, N-acetylmannosamine; NanK, N-acetylmannosamine kinase; ManNAc-6-P, N-acetylmannosamine-6-phosphate; NanE, N-acetylmannosamine-6-P epimerase; GlcNAc-6-P, N-acetylglucosamine-6-phosphate; NagA, N-acetylglucosamine-6-phosphate deacteylase; GlcN-6-P, Glucosamine-6-phosphate; NagB, Glucosamine-6-phosphate deaminase; Fru-6-P, Fructose-6-phosphate; NeuA, CMP-N-acetylneuraminic acid synthetase; CMP-NeuAc, CMP-N-acetylneuraminic acid; NeuB, N-acetylneuraminic acid synthase; LPS, lipopolysaccharide.