Separate Pathways for O Acetylation of Polymeric and Monomeric Sialic Acids and Identification of Sialyl O-Acetyl Esterase in Escherichia coli K1

Laboratory of Sialobiology, Department of Pathobiology, University of Illinois at Urbana-Champaign, 2522 VMBSB, 2001 South Lincoln Avenue, Urbana, IL 61802, USA.
Journal of Bacteriology (Impact Factor: 2.81). 10/2006; 188(17):6195-206. DOI: 10.1128/JB.00466-06
Source: PubMed


O acetylation at carbon positions 7 or 9 of the sialic acid residues in the polysialic acid capsule of Escherichia coli K1 is catalyzed by a phase-variable contingency locus, neuO, carried by the K1-specific prophage, CUS-3. Here we describe a novel method for analyzing polymeric sialic acid O acetylation
that involves the release of surface sialic acids by endo-N-acetylneuraminidase digestion, followed by fluorescent labeling and detection of quinoxalinone derivatives by chromatography.
The results indicated that NeuO is responsible for the majority of capsule modification that takes place in vivo. However,
a minor neuO-independent O acetylation pathway was detected that is dependent on the bifunctional polypeptide encoded by neuD. This pathway involves O acetylation of monomeric sialic acid and is regulated by another bifunctional enzyme, NeuA, which
includes N-terminal synthetase and C-terminal sialyl O-esterase domains. A homologue of the NeuA C-terminal domain (Pm1710) in Pasteurella multocida was also shown to be an esterase, suggesting that it functions in the catabolism of acetylated environmental sialic acids.
Our combined results indicate a previously unexpected complexity in the synthesis and catabolism of microbial sialic and polysialic
acids. These findings are key to understanding the biological functions of modified sialic acids in E. coli K1 and other species and may provide new targets for drug or vaccine development.

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Available from: Willie F Vann, Mar 12, 2014
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    • " incorporated into poly - mers ( Song et al . 2011 ) . The gene neuS in the region 2 of the kps cluster encodes alpha - Neu5Ac alpha - 2 , 8 - sialyltransferase ( NeuS ) . NeuS is responsible for polymerization of a homopol - ymer of α - 2 , 8 - linked Neu5Ac . NeuD , NeuA , and NeuS are key components of the PSA biosynthetic pathway ( Fig . 1 ) ( Steenbergen et al . 2006 ; Song et al . 2011 ; Ferrero and Aparicio 2010 ) . We assumed that the production of PSA could be en - hanced by strengthening the PSA biosynthetic pathway and tested the hypothesis in this study . Neu5Ac is the precursor for the synthesis of PSA . In bac - teria , Neu5Ac is synthesized by Neu5Ac aldolase ( NanA ) ( Tao et al . 2011 ) "
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    ABSTRACT: A number of reports have described the production of polysialic acid (PSA), focusing on the fermentation and purification of PSA. However, little work has been done to strengthen the synthetic pathway of PSA to improve PSA production. In this study, an efficient process for enhanced production of PSA using a recombinant Escherichia coli strain was developed. To improve the PSA production efficiency, the key enzymes of PSA synthetic pathway were overexpressed separately or in combination, including N-acetylneuraminate (Neu5Ac) 7-O(or 9-O)-acetyltransferase (NeuD), CMP-Neu5Ac synthetase (NeuA), and alpha-Neu5Ac alpha-2,8-sialyltransferase (NeuS). The PSA production was significantly improved by coexpression of NeuD and NeuA. In terms of the efficiency, NeuD was considered as the most important factor. Secondly, the competing pathway of intermediate Neu5Ac was blocked by nanA deletion. The efficient PSA-producing strain E. coli SA9ΔnanA/pDB1S-DA was constructed, and 16.15 ± 1.45 g/L PSA was obtained in the fed-batch culture. The production of PSA by engineered strain was increased by 85 % compared to the original strain. These results provide evidence for improvement of PSA production by regulation of the PSA biosynthetic pathway. The high productivity of our process should make it a promising cost-effective resource for PSA.
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    • "Then, the K1 antigen has, in addition to its well-recognized serum resistance and antiphagocytic properties, a role in the traversal of E. coli across the blood-brain barrier as a live bacterium (Hoffman et al. 1999; Willis and Whitfield 2013). The K1 antigen is an important virulence determinant of E. coli strains and has been shown to be associated with a variety of extraintestinal diseases (Steenbergen et al. 2006). Capsule expression in E. coli has a role in virulence during urinary tract infection (UTI) and contributes to E. coli UTI pathogenesis by promoting biofilmlike bacterial communities in the host (Ulett et al. 2013). "
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    ABSTRACT: The K1 antigen is an important virulence determinant of Escherichia coli strains and has been shown to be associated particularly with neonatal meningitis, bacteraemia and septicaemia. Thus, its detection seems to be useful, especially in the case of E. coli strains isolated from pregnant women and newborns. In this study, the sensitivity and specificity of the latex agglutination test (Pastorex Meningitis) for identification of E. coli serogroup K1 were assessed, using PCR as the gold standard. Our results showed that consistency of results between latex agglutination test and PCR amounted to 98.5 %. Therefore, Pastorex Meningitis is a good alternative to PCR and could be used for rapid K1 antigen detection, especially in local non-specialized laboratories with limited resources where PCR assay is not applied.
    Full-text · Article · Apr 2014 · Folia Microbiologica
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    • "Discerning the true function of NanS was made possible by two key observations: a commercially available source of Neu5,9Ac2 and a bioinformatics survey of nanS against the microbial genomic database which identified weak similarity to an acetyl xylan esterase (axe) [8]. Because esterases frequently share conserved primary structural similarities including active site residues [90], it was logical that NanS might be a sialate O-acetyl esterase because it mapped within a NanR-coregulated operon and was at least partly similar to Axe [88]. Remarkably, when NanS is screened against its close bacterial relatives none has a discernable copy of nanS despite the presence of genetic information known to or to potentially encode and regulate the canonical Neu5Ac dissimilatory pathway (Figures 8 and 9). "
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    ABSTRACT: Sialic acids are structurally diverse nine-carbon ketosugars found mostly in humans and other animals as the terminal units on carbohydrate chains linked to proteins or lipids. The sialic acids function in cell-cell and cell-molecule interactions necessary for organismic development and homeostasis. They not only pose a barrier to microorganisms inhabiting or invading an animal mucosal surface, but also present a source of potential carbon, nitrogen, and cell wall metabolites necessary for bacterial colonization, persistence, growth, and, occasionally, disease. The explosion of microbial genomic sequencing projects reveals remarkable diversity in bacterial sialic acid metabolic potential. How bacteria exploit host sialic acids includes a surprisingly complex array of metabolic and regulatory capabilities that is just now entering a mature research stage. This paper attempts to describe the variety of bacterial sialometabolic systems by focusing on recent advances at the molecular and host-microbe-interaction levels. The hope is that this focus will provide a framework for further research that holds promise for better understanding of the metabolic interplay between bacterial growth and the host environment. An ability to modify or block this interplay has already yielded important new insights into potentially new therapeutic approaches for modifying or blocking bacterial colonization or infection.
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