scholarly journals Genetic Analysis of the rkp-3 Gene Region in Sinorhizobium meliloti 41: rkpY Directs Capsular Polysaccharide Synthesis to KR5 Antigen Production

2009 ◽  
Vol 22 (11) ◽  
pp. 1422-1430 ◽  
Author(s):  
Adrienn Pálvölgyi ◽  
Veronika Deák ◽  
Véréna Poinsot ◽  
Tibor Nagy ◽  
Enik Nagy ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Capsular Polysaccharide ◽  
Low Molecular Weight ◽  
Capsular Polysaccharides ◽  
Genetic Dissection ◽  
Sequence Determination ◽  
Polysaccharide Synthesis ◽  
Surface Polysaccharides ◽  
Pseudaminic Acid ◽  
And Function

Rhizobial surface polysaccharides, including capsular polysaccharides (KPS), are involved in symbiotic infection. The rkp-3 locus of Sinorhizobium meliloti 41 is responsible for the production of pseudaminic acid, one of the components of the KR5 antigen, a strain-specific KPS. We have extended the sequence determination and genetic dissection of the rkp-3 region to clarify the structure and function of the rkpY gene and to identify additional rkp genes. Except for rkpY, no other genes were found where mutation affected the KPS structure and symbiosis. These mutants show a unique phenotype producing a low molecular weight polysaccharide (LMW PS). Creating double mutants, we have shown that biosynthesis genes of the KR5 antigen except rkpZ are not necessary for the production of this LMW PS. Polysaccharide analysis of genetically modified strains suggests that rkpY has pleiotropic effects on polysaccharide production. It directs KPS synthesis to the KR5 antigen and influences lipo-oligo 3-deoxy-d-manno-2 octulosonic acid (Kdo) production in S. meliloti 41. In addition, rkpY suppresses the lipo-oligoKdo production when it is introduced into S. meliloti 1021.

scholarly journals Immunochemical and Biological Characterization of Three Capsular Polysaccharides from a Single Bacteroides fragilisStrain

2001 ◽  
Vol 69 (4) ◽  
pp. 2339-2344 ◽  
Author(s):  
Wiltrud M. Kalka-Moll ◽  
Ying Wang ◽  
L. E. Comstock ◽  
Sylvia E. Gonzalez ◽  
Arthur O. Tzianabos ◽  
...  
Keyword(s):  
Capsular Polysaccharide ◽  
Basic Structure ◽  
Structural Features ◽  
Capsular Polysaccharides ◽  
Polysaccharide Complex ◽  
Abdominal Abscesses ◽  
Colonic Flora ◽  
Surface Polysaccharides ◽  
Normal Human ◽  
Net Charges

ABSTRACT Although Bacteroides fragilis accounts for only 0.5% of the normal human colonic flora, it is the anaerobic species most frequently isolated from intra-abdominal and other infections with an intestinal source. The capsular polysaccharides of B. fragilis are part of a complex of surface polysaccharides and are the organism's most important virulence factors in the formation of intra-abdominal abscesses. Two capsular polysaccharides from strain NCTC 9343, PS A1 and PS B1, have been characterized structurally. Their most striking feature is a zwitterionic charge motif consisting of both positively and negatively charged substituent groups on each repeating unit. This zwitterionic motif is essential for abscess formation. In this study, we sought to elucidate structural features of the capsular polysaccharide complex of a commonly studied B. fragilisstrain, 638R, that is distinct from strain 9343. We sought a more general picture of the species to establish basic structure-activity and structure-biosynthesis relationships among abscess-inducing polysaccharides. Strain 638R was found to have a capsular polysaccharide complex from which three distinct carbohydrates could be isolated by a complex purification procedure. Compositional and immunochemical studies demonstrated a zwitterionic charge motif common to all of the capsular polysaccharides that correlated with their ability to induce experimental intra-abdominal abscesses. Of interest is the range of net charges of the isolated polysaccharides—from positive (PS C2) to balanced (PS A2) to negative (PS 3). Relationships among structural components of the zwitterionic polysaccharides and their molecular biosynthesis loci were identified.

scholarly journals The rkp-1 Cluster Is Required for Secretion of Kdo Homopolymeric Capsular Polysaccharide in Sinorhizobium meliloti Strain Rm1021

2009 ◽  
Vol 191 (22) ◽  
pp. 6988-7000 ◽  
Author(s):  
Maike G. Müller ◽  
Lennart S. Forsberg ◽  
David H. Keating
Keyword(s):  
Soil Bacteria ◽  
Sinorhizobium Meliloti ◽  
Capsular Polysaccharide ◽  
Root Nodules ◽  
Nitrogen Stress ◽  
Capsular Polysaccharides ◽  
Leguminous Plants ◽  
Endosymbiotic Bacteria ◽  
Meliloti Strain ◽  
Intracellular Polysaccharide

ABSTRACT Under conditions of nitrogen stress, leguminous plants form symbioses with soil bacteria called rhizobia. This partnership results in the development of structures called root nodules, in which differentiated endosymbiotic bacteria reduce molecular dinitrogen for the host. The establishment of rhizobium-legume symbioses requires the bacterial synthesis of oligosaccharides, exopolysaccharides, and capsular polysaccharides. Previous studies suggested that the 3-deoxy-d-manno-oct-2-ulopyranosonic acid (Kdo) homopolymeric capsular polysaccharide produced by strain Sinorhizobium meliloti Rm1021 contributes to symbiosis with Medicago sativa under some conditions. However, a conclusive symbiotic role for this polysaccharide could not be determined due to a lack of mutants affecting its synthesis. In this study, we have further characterized the synthesis, secretion, and symbiotic function of the Kdo homopolymeric capsule. We showed that mutants lacking the enigmatic rkp-1 gene cluster fail to display the Kdo capsule on the cell surface but accumulate an intracellular polysaccharide of unusually high M r. In addition, we have demonstrated that mutations in kdsB2, smb20804, and smb20805 affect the polymerization of the Kdo homopolymeric capsule. Our studies also suggest a role for the capsular polysaccharide in symbiosis. Previous reports have shown that the overexpression of rkpZ from strain Rm41 allows for the symbiosis of exoY mutants of Rm1021 that are unable to produce the exopolysaccharide succinoglycan. Our results demonstrate that mutations in the rkp-1 cluster prevent this phenotypic suppression of exoY mutants, although mutations in kdsB2, smb20804, and smb20805 have no effect.

scholarly journals The rkp-3 Gene Region of Sinorhizobium meliloti Rm41 Contains Strain-Specific Genes that Determine K Antigen Structure

2001 ◽  
Vol 14 (12) ◽  
pp. 1395-1403 ◽  
Author(s):  
Ernő Kiss ◽  
Attila Kereszt ◽  
Fatime Barta ◽  
Samuel Stephens ◽  
Bradley L. Reuhs ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Capsular Polysaccharide ◽  
Amino Acid Sequences ◽  
Open Reading Frames ◽  
Gene Region ◽  
Polysaccharide Synthesis ◽  
Polysaccharide K ◽  
High Degree ◽  
K Antigen ◽  
Antigen Structure

The rkp-3 region is indispensable for capsular polysaccharide (K antigen) synthesis in Sinorhizobium meliloti Rm41. Strain Rm41 produces a K antigen of strain-specific structure, designated as the KR5 antigen. The data in this report show that the rkp-3 gene region comprises 10 open reading frames involved in bacterial polysaccharide synthesis and export. The predicted amino acid sequences for the rkpL-Q gene products are homologous to enzymes involved in the production of specific sugar moieties, while the putative products of the rkpRST genes show a high degree of similarity to proteins required for transporting polysaccharides to the cell surface. Southern analysis experiments using gene-specific probes suggest that genes involved in the synthesis of the precursor sugars are unique in strain Rm41, whereas sequences coding for export proteins are widely distributed among Sinorhizobium species. Mutations in the rkpL-Q genes result in a modified K antigen pattern and impaired symbiotic capabilities. On this basis, we suggest that these genes are required for the production of the KR5 antigen that is necessary for S. meliloti Rm41 exoB (AK631)-alfalfa (Medicago sativa) symbiosis.

Functional design of glycan-conjugated molecules using a chemoenzymatic approach

2021 ◽  
Author(s):  
Makoto Ogata
Keyword(s):  
Molecular Weight ◽  
Large Scale ◽  
Biological Activities ◽  
Natural Compounds ◽  
Low Molecular Weight ◽  
Functional Design ◽  
Enzymatic Method ◽  
Conjugated Molecules ◽  
Design Synthesis ◽  
And Function

Abstract Carbohydrates play important and diverse roles in the fundamental processes of life. We have established a method for accurately and a large scale synthesis of functional carbohydrates with diverse properties using a unique enzymatic method. Furthermore, various artificial glycan-conjugated molecules have been developed by adding these synthetic carbohydrates to macromolecules and to middle and low molecular weight molecules with different properties. These glycan-conjugated molecules have biological activities comparable to or higher than those of natural compounds, and present unique functions. In this review, several synthetic glycan-conjugated molecules are taken as examples to show design, synthesis and function.

scholarly journals Structure and antimicrobial activity of NCR169, a nodule-specific cysteine-rich peptide of Medicago truncatula

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Noriyoshi Isozumi ◽  
Yuya Masubuchi ◽  
Tomohiro Imamura ◽  
Masashi Mori ◽  
Hironori Koga ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Medicago Truncatula ◽  
Mechanism Of Action ◽  
Disulfide Bonds ◽  
Sinorhizobium Meliloti ◽  
Bound State ◽  
Disulfide Linkage ◽  
Model Legume ◽  
Nmr Structures ◽  
And Function

AbstractA model legume, Medicago truncatula, has over 600 nodule-specific cysteine-rich (NCR) peptides required for symbiosis with rhizobia. Among them, NCR169, an essential factor for establishing symbiosis, has four cysteine residues that are indispensable for its function. However, knowledge of NCR169 structure and mechanism of action is still lacking. In this study, we solved two NMR structures of NCR169 caused by different disulfide linkage patterns. We show that both structures have a consensus C-terminal β-sheet attached to an extended N-terminal region with dissimilar features; one moves widely, whereas the other is relatively stapled. We further revealed that the disulfide bonds of NCR169 contribute to its structural stability and solubility. Regarding the function, one of the NCR169 oxidized forms could bind to negatively charged bacterial phospholipids. Furthermore, the positively charged lysine-rich region of NCR169 may be responsible for its antimicrobial activity against Escherichia coli and Sinorhizobium meliloti. This active region was disordered even in the phospholipid bound state, suggesting that the disordered conformation of this region is key to its function. Morphological observations suggested the mechanism of action of NCR169 on bacteria. The present study on NCR169 provides new insights into the structure and function of NCR peptides.

Implant Infections Due to Enterococci: Role of Capsular Polysaccharides and Biofilm

2005 ◽  
Vol 28 (11) ◽  
pp. 1079-1090 ◽  
Author(s):  
F. Fabretti ◽  
J. Huebner
Keyword(s):  
Antimicrobial Agents ◽  
Capsular Polysaccharide ◽  
Female Genital Tract ◽  
Teichoic Acid ◽  
Capsular Polysaccharides ◽  
Human Pathogens ◽  
Artificial Joints ◽  
Artificial Hearts ◽  
Intravascular Catheters ◽  
Enterococcal Infections

Enterococci are natural inhabitants of the gastrointestinal tract and of the female genital tract of humans and many animals. In recent years, enterococci have been increasingly recognized as important human pathogens causing infections associated with medical devices. Their resistance to most antimicrobial agents and their ability to form biofilm has contributed to the increasing incidence of nosocomial enterococcal infections. Enterococci possess a capsular polysaccharide composed of a glycerol-teichoic acid-like molecule consisting of repeating units of 6-α-D-glucose-1-2-glycerol-3-PO4, substituted on carbon 2 with a α-2,1-linked molecule of glucose. Using both immunologic and genetic data E. faecalis can be assigned to specific serotypes based on capsular polysaccharides. Clinical examples of foreign-body infections due to enterococci are described, comprising infections of artificial joints, implanted intravascular catheters, artificial hearts and artificial valves, stents, liquor shunt devices, and intraocular infections. Methods to prevent and/or treat enterococcal infections are presented.

Polyamine metabolism and function

1982 ◽  
Vol 243 (5) ◽  
pp. C212-C221 ◽  
Author(s):  
A. E. Pegg ◽  
P. P. McCann
Keyword(s):  
Molecular Weight ◽  
Tissue Growth ◽  
Polyamine Metabolism ◽  
Organic Cations ◽  
Low Molecular Weight ◽  
Polyamine Biosynthesis ◽  
Polyamine Content ◽  
And Function ◽  
Specific Inhibitors

Polyamines are ubiquitous organic cations of low molecular weight. The content of these amines is closely regulated by the cell according to the state of growth. The reactions responsible for the biosynthesis and interconversion of the polyamines and their precursor putrescine are described and the means by which polyamine content can be varied in response to exogenous stimuli are discussed. The role of polyamines in the cell cycle, cell division, tissue growth, and differentiation is considered. Recent studies using highly specific inhibitors of polyamine biosynthesis such as alpha-difluoromethylornithine to prevent accumulation of polyamines have indicated that the synthesis of polyamines is intimately associated with these processes. Such inhibitors have great potential for investigation of the cellular role of polyamines.

scholarly journals Diversity and evolution of surface polysaccharide synthesis loci in Enterobacteriales

2019 ◽  
Author(s):  
Kathryn E. Holt ◽  
Florent Lassalle ◽  
Kelly L. Wyres ◽  
Ryan Wick ◽  
Rafal J. Mostowy
Keyword(s):  
Evolutionary Dynamics ◽  
Bacterial Species ◽  
Purifying Selection ◽  
Evolutionary Forces ◽  
Polysaccharide Synthesis ◽  
Surface Polysaccharides ◽  
Surface Polysaccharide ◽  
Selective Preservation ◽  
Multiple Species

Bacterial capsules and lipopolysaccharides are diverse surface polysaccharides (SPs) that serve as the frontline for interactions with the outside world. While SPs can evolve rapidly, their diversity and evolutionary dynamics across different taxonomic scales has not been investigated in detail. Here, we focused on the bacterial order Enterobacteriales (including the medically-relevant Enterobacteriaceae), to carry out comparative genomics of two SP locus synthesis regions, cps and kps, using 27,334 genomes from 45 genera. We identified high-quality cps loci in 22 genera and kps in 11 genera, around 4% of which were detected in multiple species. We found SP loci to be highly dynamic genetic entities: their evolution was driven by high rates of horizontal gene transfer (HGT), both of whole loci and component genes, and relaxed purifying selection, yielding large repertoires of SP diversity. In spite of that, we found the presence of (near-)identical locus structures in distant taxonomic backgrounds that could not be explained by recent exchange, pointing to long-term selective preservation of locus structures in some populations. Our results reveal differences in evolutionary dynamics driving SP diversity within different bacterial species, with lineages of Escherichia coli, Enterobacter hormachei and Klebsiella aerogenes most likely to share SP loci via recent exchange; and lineages of Salmonella enterica, Citrobacter sakazakii and Serratia marcescens most likely to share SP loci via other mechanisms such as long-term preservation. Overall, the evolution of SP loci in Enterobacteriales is driven by a range of evolutionary forces and their dynamics and relative importance varies between different species.

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