The structure of Cryptococcus neoformans galactoxylomannan contains beta-D-glucuronic acid

Analytical Services/Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA.
Carbohydrate research (Impact Factor: 1.93). 04/2009; 344(7):915-20. DOI: 10.1016/j.carres.2009.03.003
Source: PubMed


The structure of galactoxylomannan, a capsular polysaccharide from the opportunistic yeast Cryptococcus neoformans, was re-examined by NMR spectroscopy and GC-MS. The residue that is 3-linked to the side chain galactose and was previously assigned as beta-D-xylose [Vaishnav, V. V.; Bacon, B. E.; O'Neill, M.; Cherniak, R. Carbohydr. Res.1998, 306, 315-330] was determined to be beta-D-glucuronic acid. A revised structure for this polymer is presented, along with a proposal that this compound be termed glucuronoxylomannogalactan (GXMGal).

Download full-text


Available from: Tamara Doering,
  • Source
    • "Samples were precipitated with cold 70% ethanol for 2 h, centrifuged at 15 000 × g, pellet dried and frozen at –80˚C until analysis. Glycosyl composition (Santander et al., 2013) and linkage ('methylation') (Heiss et al., 2009) analysis were performed as described previously. For NMR, the samples (~20 mg each) were deuteriumexchanged twice from D 2 O (99.9% D, Sigma-Aldrich, "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cyanobacterial organic matter excretion is crucial to carbon cycling in many microbial communities, but the nature and bioavailability of this C depend on unknown physiological functions. Cyanobacteria-dominated hypersaline laminated mats are a useful model ecosystem for the study of C flow in complex communities, as they use photosynthesis to sustain a more or less closed system. Although such mats have a large C reservoir in the extracellular polymeric substances (EPSs), the production and degradation of organic carbon is not well defined. To identify extracellular processes in cyanobacterial mats, we examined mats collected from Elkhorn Slough (ES) at Monterey Bay, California, for glycosyl and protein composition of the EPS. We found a prevalence of simple glucose polysaccharides containing either α or β (1,4) linkages, indicating distinct sources of glucose with differing enzymatic accessibility. Using proteomics, we identified cyanobacterial extracellular enzymes, and also detected activities that indicate a capacity for EPS degradation. In a less complex system, we characterized the EPS of a cyanobacterial isolate from ES, ESFC-1, and found the extracellular composition of biofilms produced by this unicyanobacterial culture were similar to that of natural mats. By tracing isotopically labeled EPS into single cells of ESFC-1, we demonstrated rapid incorporation of extracellular-derived carbon. Taken together, these results indicate cyanobacteria reuse excess organic carbon, constituting a dynamic pool of extracellular resources in these mats.The ISME Journal advance online publication, 23 October 2015; doi:10.1038/ismej.2015.180.
    The ISME Journal 10/2015; DOI:10.1038/ismej.2015.180 · 9.30 Impact Factor
  • Source
    • "Cryptococcal PS can be secreted via the protein secretory pathway ( Yoneda and Doering , 2006 ; Panepinto et al. , 2009 ) , or shed from cells in association with vesicular structures ( Rodrigues et al . , 2007 ) , and consists of at least two types of polymers : glucuronoxylomannan ( GXM ) and glucuronoxylomannogalactan ( GXMGal ; Heiss et al . , 2009 ) . Despite the homogenous appearance of the capsule by light microscopy , electron microscopy ( EM ) data suggest that the capsule is a heterogeneous structure , with a clear vertical " stratification " of the matrix into an electron - dense inner layer and an electron - lucent outer layer ( Gates et al . , 2004 ; Bryan et al . , 2005 "
    [Show abstract] [Hide abstract]
    ABSTRACT: The fungal pathogen Cryptococcus neoformans causes life-threatening infections in immunocompromised individuals, representing one of the leading causes of morbidity and mortality in AIDS patients. The main virulence factor of C. neoformans is the polysaccharide capsule; however, many fundamental aspects of capsule structure and function remain poorly understood. Recently, important capsule properties were uncovered using optical tweezers and other biophysical techniques, including dynamic and static light scattering, zeta potential and viscosity analysis. This review provides an overview of the latest findings in this emerging field, explaining the impact of these findings on our understanding of C. neoformans biology and resistance to host immune defenses.
    Frontiers in Microbiology 06/2015; 6:640. DOI:10.3389/fmicb.2015.00640 · 3.99 Impact Factor
  • Source
    • "Samples were read at a wavelength of 620 nm, and glucose was used as a standard to estimate carbohydrate levels in the samples. Finally, dried EPS samples were sent to the Complex Carbohydrate Research Center (Athens, GA, USA) for determination of monosaccharide composition (Santander et al., 2013), linkage (Heiss et al., 2009) and NMR analysis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Elevated levels of the second messenger c-di-GMP activate biosynthesis of an unknown exopolysaccharide (EPS) in the food-borne pathogen Listeria monocytogenes. This EPS strongly protects cells against disinfectants and desiccation, indicating its potential significance for listerial persistence in the environment and for food safety. We analyzed the potential phylogenetic origin of this EPS, determined its complete structure, characterized genes involved in its biosynthesis and hydrolysis, and identified diguanylate cyclases activating its synthesis. Phylogenetic analysis of EPS biosynthesis proteins suggests that they have evolved within monoderms. Scanning electron microscopy revealed that L. monocytogenes EPS is cell surface-bound. Secreted carbohydrates represent exclusively cell-wall debris. Based on carbohydrate composition, linkage and NMR analysis, the structure of the purified EPS is identified as a β-1,4-linked N-acetylmannosamine chain decorated with terminal α-1,6-linked galactose. All genes of the pssA-E operon are required for EPS production and so is a separately located pssZ gene. We show that PssZ has an EPS-specific glycosylhydrolase activity. Exogenously added PssZ prevents EPS-mediated cell aggregation and disperses preformed aggregates, whereas an E72Q mutant in the presumed catalytic residue is much less active. The diguanylate cyclases DgcA and DgcB, whose genes are located next to pssZ, are primarily responsible for c-di-GMP-dependent for EPS production. This article is protected by copyright. All rights reserved.
    Molecular Microbiology 02/2015; 96(4). DOI:10.1111/mmi.12966 · 4.42 Impact Factor
Show more