Although these studies have not been independently confirmed, the combined evidence suggests that the metabolism of host-derived sialic acids plays an at least minor to potentially defining role in different bacterial infections. Other studies, using a variety of bacterial species, support the idea that the metabolism of host-derived sialic acid is important to colonization or disease (see reference 8 and references cited therein). The essential role of sialic acid transport in disease has been independently confirmed ( 7). Our laboratory discovered ( 1, 2) and later characterized the transport and metabolism of exogenous N-acetylneuraminic acid (Neu5Ac) in Escherichia coli, Haemophilus influenzae, and Pasteurella multocida ( 3, – 6), providing also the first evidence that these processes are essential for animal disease. This expansion of the nanS superfamily suggests important, although as-yet-unknown, functions in host-microbe interactions. Therefore, these original results extend our previous studies of nanS to include mucosal pathogens, prophage, and prophage remnants. The unexpected diversity of these enzymes suggests new avenues for investigating host-bacterium interactions. Our results further show that nanS homologs exist in bacteria other than Escherichia coli, as well as part of toxigenic E. Our results show that the catabolism of the diacetylated form of host sialic acid requires a specialized esterase, NanS. Available evidence indicates that diverse bacterial species use host sialic acids for adhesion or as sources of carbon and nitrogen.
These sugars occur primarily as terminal carbohydrate residues on host glycoproteins and glycolipids. IMPORTANCE The sialic acids are a family of over 40 naturally occurring 9-carbon keto-sugars that function in a variety of host-bacterium interactions. also encode active esterase, demonstrating an unexpected diversity of bacterial sialate O-acetyl esterase. We further demonstrate that nanS homologs in Streptococcus spp. coli O157 nanS mutant on O-acetylated sialic acid. coli strain K-12 nanS mutant and the unimpaired growth of an E. These paralogs may include sequences encoding N- or C-terminal domains of unknown function where the NanS domains can act as sialate O-acetyl esterases, as shown by complementation of an E.
coli strain O157:H7 Stx prophage or prophage remnants invariably include paralogs of nanS often located downstream of the Shiga-like toxin genes. Using a similar approach, we show that E. Here, we demonstrate the esterase activity of Escherichia coli NanS after purifying it as a C-terminal HaloTag fusion. Bacteria with O-acetyl sialate esterase(s) utilize acetylated sialic acids for growth, thereby gaining a presumed metabolic advantage over competitors lacking this activity. Modified sialic acids produce challenges for colonizing bacteria, because the chemical alterations to N-acetylneuraminic acid (Neu5Ac) confer increased resistance to sialidase and aldolase activities essential for the catabolism of host sialic acids. Each form may be modified by acetyl esters at carbon position 4, 7, 8, or 9 and by a variety of less-common modifications. Bacterial commensals and pathogens exploit host sialic acids for nutrition, adhesion, or antirecognition, where N-acetyl- or N-glycolylneuraminic acids are the two predominant chemical forms of sialic acids. The sialic acids ( N-acylneuraminates) are a group of nine-carbon keto-sugars existing mainly as terminal residues on animal glycoprotein and glycolipid carbohydrate chains.
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