Bacterial Exopolysaccharides: Functionality and Prospects

Nwodo, Uchechukwu U.; Green, Ezekiel; Okoh, Anthony I.

doi:10.3390/ijms131114002

Cited by 521 publications

(269 citation statements)

References 55 publications

(66 reference statements)

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“…adding structural integrity to the cell, aiding in cell adherence to biotic and abiotic surfaces, and improving migration of cells in liquid and communal life in biofilms. 110 For many encapsulated bacteria, polysaccharides are major determinants for survival, promoting host virulence, protection from desiccation, and protection from phagocytosis and antimicrobials. [111][112][113] For phage, polysaccharides can pose as a physical barrier to the cell surface receptors needed for adsorption.…”

Section: Virion-associated Peptidoglycan Hydrolasesmentioning

confidence: 99%

Antimicrobial bacteriophage-derived proteins and therapeutic applications

2015

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Section: Virion-associated Peptidoglycan Hydrolasesmentioning

confidence: 99%

Antimicrobial bacteriophage-derived proteins and therapeutic applications

2015

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“…Five-gram (wet weight) amounts of soil from each sample (BHS and PP soils) plus 0.5% (wt/wt) cellulose or B. indica EPS ( 13 C-labeled or 12 C-labeled controls) were distributed into 120-ml serum bottles, which were sealed and made gas tight with butyl rubber stoppers. The soil was moistened with 1 ml of sterile deionized water per bottle.…”

Section: Soilsmentioning

confidence: 99%

“…Bacteria produce exopolysaccharides (EPSs) to serve a variety of functions, including surface attachment, biofilm formation, desiccation resistance, and cryoprotection. EPSs may also serve as an energy reserve or as a diffusive barrier to harmful chemicals (11,12). These substances have received scientific interest primarily due to their biotechnological applications (13).…”

mentioning

confidence: 99%

Stable-Isotope Probing Identifies Uncultured Planctomycetes as Primary Degraders of a Complex Heteropolysaccharide in Soil

Wang

Sharp

Jones

et al. 2015

Appl Environ Microbiol

154

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The exopolysaccharides (EPSs) produced by some bacteria are potential growth substrates for other bacteria in soil. We used stable-isotope probing (SIP) to identify aerobic soil bacteria that assimilated the cellulose produced by Gluconacetobacter xylinus or the EPS produced by Beijerinckia indica. The latter is a heteropolysaccharide comprised primarily of L-guluronic acid, D-glucose, and D-glycero-D-mannoheptose.13 C-labeled EPS and 13 C-labeled cellulose were purified from bacterial cultures grown on [ 13 C]glucose. Two soils were incubated with these substrates, and bacteria actively assimilating them were identified via pyrosequencing of 16S rRNA genes recovered from 13 C-labeled DNA. Cellulose C was assimilated primarily by soil bacteria closely related (93 to 100% 16S rRNA gene sequence identities) to known cellulose-degrading bacteria. However, B. indica EPS was assimilated primarily by bacteria with low identities (80 to 95%) to known species, particularly by different members of the phylum Planctomycetes. In one incubation, members of the Planctomycetes made up >60% of all reads in the labeled DNA and were only distantly related (<85% identity) to any described species. Although it is impossible with SIP to completely distinguish primary polysaccharide hydrolyzers from bacteria growing on produced oligo-or monosaccharides, the predominance of Planctomycetes suggested that they were primary degraders of EPS. Other bacteria assimilating B. indica EPS included members of the Verrucomicrobia, candidate division OD1, and the Armatimonadetes. The results indicate that some uncultured bacteria in soils may be adapted to using complex heteropolysaccharides for growth and suggest that the use of these substrates may provide a means for culturing new species. Some major phyla of the domain Bacteria, like the Proteobacteria and Actinobacteria, are well-known from cultivation studies. Others, like Acidobacteria, Verrucomicrobia, and Planctomycetes, have few cultured species, although they make up large proportions of the bacterial 16S rRNA genes detected in environments such as soil (1). One theory proposed to explain the difficulty in culturing bacteria from these phyla is that most are K selected as opposed to r selected. Typical r-selected bacteria grow rapidly on simple monomeric substrates in nutrient-rich environments, conditions presented by most microbiological media (2, 3). On the other hand, K-selected bacteria have a more efficient cell metabolism and strong competitive ability and grow slowly on recalcitrant, complex substances (3-5). Several studies have demonstrated that members of difficult-to-culture phyla like Acidobacteria, Verrucomicrobia, and Planctomycetes can be cultivated using polysaccharides, such as xylan, xanthan, and pectin, as energy sources (e.g., see references 6 to 8). The heteropolysaccharide gellan, which is often used as a gelling agent as an alternative to agar, can also act as an energy source for some soil bacteria (9), in part explaining the observation that it improves cultu...

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“…The term "CPS" refers here to cell-attached glycoconjugates whether or not they form a true capsule that can be visualized by electron microscopy. There is growing awareness of the role played by CPS and EPS in cross talk among bacteria and between the bacterium and its host cell or the overall environment (2,3). In various bacterial models, secreted polysaccharides were shown to modulate the intrinsic properties of the producing bacteria (surface adhesion, biofilm formation, resistance to host immune defenses such as phagocytosis and serum killing) as well as the host cell response through immunomodulation.…”

mentioning

confidence: 99%

Mycoplasma agalactiae Secretion of β-(1→6)-Glucan, a Rare Polysaccharide in Prokaryotes, Is Governed by High-Frequency Phase Variation

Gaurivaud

Baranowski

Pau-Roblot

et al. 2016

Appl Environ Microbiol

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Mycoplasmas are minimal, wall-less bacteria but have retained the ability to secrete complex carbohydrate polymers that constitute a glycocalyx. In members of the Mycoplasma mycoides cluster, which are important ruminant pathogens, the glycocalyx includes both cell-attached and cell-free polysaccharides. This report explores the potential secretion of polysaccharides by M. agalactiae, another ruminant pathogen that belongs to a distant phylogenetic group. Comparative genomic analyses showed that M. agalactiae possesses all the genes required for polysaccharide secretion. Notably, a putative synthase gene (gsmA) was identified, by in silico reconstruction of the biosynthetic pathway, that could be involved in both polymerization and export of the carbohydrate polymers. M. agalactiae polysaccharides were then purified in vitro and found to be mainly cell attached, with a linear ␤-(1¡6)-glucopyranose structure [␤-(1¡6)-glucan]. Secretion of ␤-(1¡6)-glucan was further shown to rely on the presence of a functional gsmA gene, whose expression is subjected to high-frequency phase variation. This event is governed by the spontaneous intraclonal variation in length of a poly(G) tract located in the gsmA coding sequence and was shown to occur in most of the M. agalactiae clinical isolates tested in this study. M. agalactiae susceptibility to serum-killing activity appeared to be dictated by ON/OFF switching of ␤-(1¡6)-glucan secretion, suggesting a role of this phenomenon in survival of the pathogen when it invades the host bloodstream. Finally, ␤-(1¡6)-glucan secretion was not restricted to M. agalactiae but was detected also in M. mycoides subsp. capri PG3 T , another pathogen of small ruminants. IMPORTANCEMany if not all bacteria are able to secrete polysaccharides, either attached to the cell surface or exported unbound into the extracellular environment. Both types of polysaccharides can play a role in bacterium-host interactions. Mycoplasmas are no exception despite their poor overall metabolic capacity. We showed here that M. agalactiae secretes a capsular ␤-(1¡6)-glucopyranose thanks to a specific glycosyltransferase with synthase activity. This secretion is governed by high-frequency ON/OFF phase variation that might be crucial in mycoplasma host dissemination, as cell-attached ␤-(1¡6)-glucopyranose increases serum-killing susceptibility. Our results provide functional genetic data about mycoplasmal glycosyltransferases with dual functions, i.e., assembly and export of the sugar polymers across the cell membrane. Furthermore, we demonstrated that nonprotein epitopes can be subjected to surface antigenic variation in mycoplasmas. Finally, the present report contributes to unravel the role of secreted polysaccharides in the virulence and pathogenicity of these peculiar bacteria.

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Bacterial Exopolysaccharides: Functionality and Prospects

Cited by 521 publications

References 55 publications

Antimicrobial bacteriophage-derived proteins and therapeutic applications

Antimicrobial bacteriophage-derived proteins and therapeutic applications

Stable-Isotope Probing Identifies Uncultured Planctomycetes as Primary Degraders of a Complex Heteropolysaccharide in Soil

Mycoplasma agalactiae Secretion of β-(1→6)-Glucan, a Rare Polysaccharide in Prokaryotes, Is Governed by High-Frequency Phase Variation

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