Extracellular Polysaccharide Component Research Articles

The extracellular polysaccharide determine the physico-chemical surface properties of Microcystis.

Microcystis possesses the capacity to form colonies and blooms in lakes and reservoirs worldwide, causing significant ecological challenges in aquatic ecosystems. However, little is known about the determining factors of physico-chemical surface properties that govern the competitive advantage of Microcystis. Here, The physico-chemical surface properties of Microcystis wesenbergii and Microcystis aeruginosa, including specific surface area (SSA), hydrophobicity, zeta potential, and functional groups were investigated. Additionally, the extracellular polysaccharide (EPS) were analyzed. Laboratory-cultured Microcystis exhibited hydrophilic, a negative zeta potential and negatively charged. Furthermore, no significant relationship was shown between these properties and the cultivation stage. Microcystis wesenbergii exhibited low free energy of cohesion, high surface free energy, high growth rate, and high EPS content during the logarithmic phase. On the other hand, M. aeruginosa displayed lower free energy of cohesion, high surface free energy, high EPS content, and high growth rate during the stationary phase. These characteristics contribute to their respective competitive advantage. Furthermore, the relationship between EPS and surface properties was investigated. The polysaccharide component of EPS primarily influenced the SSA and total surface energy of Microcystis. Likewise, the protein component of EPS influenced hydrophobicity and surface tension. The polysaccharide composition, including glucuronic acid, xylose, and fructose, mainly influenced surface properties. Additionally, hydrophilic groups such as O-H and P-O-P played a crucial role in determining hydrophobicity in Microcystis. This study elucidates that EPS influenced the SSA, hydrophobicity, and surface free energy of Microcystis cells, which in turn impact the formation of Microcystis blooms and the collection.

Bacterial cyclic β-(1,2)-glucans sequester iron to protect against iron-induced toxicity.

Cellular iron homeostasis is critical for survival and growth. Bacteria employ a variety of strategies to sequester iron from the environment and to store intracellular iron surplus that can be utilized in iron-restricted conditions while also limiting the potential for the production of iron-induced reactive oxygen species (ROS). Here, we report that membrane-derived oligosaccharide (mdo) glucan, an intrinsic component of Gram-negative bacteria, sequesters the ferrous form of iron. Iron-binding, uptake, and localization experiments indicated that both secreted and periplasmic β-(1,2)-glucans bind iron specifically and promote growth under iron-restricted conditions. Xanthomonas campestris and Escherichia coli mutants blocked in the production of β-(1,2)-glucan accumulate low amounts of intracellular iron under iron-restricted conditions, whereas they exhibit elevated ROS production and sensitivity under iron-replete conditions. Our results reveal a critical role of glucan in intracellular iron homeostasis conserved in Gram-negative bacteria.

Importance of extracellular polysaccharides on proton and Cd binding to bacterial biomass: A comparative study

The importance of extracellular polysaccharide (EPS) on proton and Cd binding was examined by comparing the adsorption behaviors of 4 bacterial species ( Pseudomonas putida, Shewenella oneidensis, Rhizobium tropici, and Agrobacterium sp. [ATCC# 21680]) with intact capsular EPS to corresponding adsorption behaviors with the EPS enzymatically removed from the biomass. Potentiometric titrations were conducted to detect any differences in proton binding of the biomass with and without the presence of EPS. Enzymatic removal of the EPS from each of the bacterial species in this study resulted in no significant differences in biomass proton binding behavior. Batch Cd adsorption experiments also showed no significant differences in the adsorption capacities between the EPS and EPS-free systems for all 4 species of bacteria. Our results suggest that EPS contains proton-active functional groups that are similar to those on the cell wall, and that, on a mass-normalized basis, EPS and bacterial cell walls exhibit similar site concentrations and affinities for adsorbing protons and Cd from solution. Because EPS exhibits similar Cd and proton binding properties to bacterial cell walls, and because of the similarity in binding properties between species, it may be possible to model metal and proton binding to biofilms in general using a single set of stability constants. This general modeling approach would obviate the impossible task of determining binding constants for protons and each metal of interest with each EPS component and each bacterial cell wall of interest.

Characterization of a Sinorhizobium isolate and its extracellular polymer implicated in pollutant transport in soil.

A bacterium isolated from soil (designated 9702-M4) synthesizes an extracellular polymer that facilitates the transport of such hydrophobic pollutants as polynuclear aromatic hydrocarbons, as well as the toxic metals lead and cadmium in soil. Biolog analysis, growth rate determinations, and percent G+C content identify 9702-M4 as a strain of Sinorhizobium meliloti. Sequence analysis of a 16S rDNA fragment gives 9702-M4 a phylogenetic designation most closely related to Sinorhizobium fredii. The extracellular polymer of isolate 9702-M4 is composed of both an extracellular polysaccharide (EPS) and a rough lipopolysaccharide. The EPS component is composed mainly of 4-glucose linkages with monomers of galactose, mannose, and glucuronic acid and has pyruval and acetyl constituents. The lipid fraction and the negative charge associated with carbonyl groups of the exopolymer are thought to account for the binding of polynuclear aromatic hydrocarbons and cationic metals.

Composition of Lipopolysaccharides from Four Strains of Erwinia amylovora

SUMMARY: The lipopolysaccharides (LPSs) from four isolates of Erwinia amylovora were examined. One isolate was virulent and capsulate, and it produced extracellular polysaccharide (EPS). Three were avirulent, of which one was capsulate and produced EPS; the remainder were non-capsulate and did not produce EPS. LPS was recovered from the cells and from the culture medium. Material extracted from the cells using phenol-water was indistinguishable from LPS extracted with phenol-chloroform-light petroleum. Acid hydrolysis released lipid A which contained in all cases glucosamine, phosphate and the fatty acids 12:0, 14:0 and 3-OH 14:0. The carbohydrate released by mild acid hydrolysis was resolved by gel permeation chromatography into three components: I, a partially included species identified as core substituted with a short sidechain of fucose, galactose and glucose; II, an unsubstituted core oligosaccharide containing heptose, glucose, uronic acid, amino compounds and 3-deoxy-2-octulosonic acid (KDO); III; a totally-included low M r fraction containing KDO, phosphate and amino compounds. The sidechain component was missing from LPS of one of the non-capsulate strains that did not produce EPS. This strain is believed to lack UDP-glucose-4-epimerase, a key enzyme in the biosynthesis of galactose. Galactose (with glucose and uronic acid) is known also to be a component of EPS. Defects in galactose synthesis may therefore affect the assembly of LPS as well as EPS.

Lack of correlation between extracellular polysaccharide and nodulation ability in Rhizobium

Rhizobia are Gram-negative bacteria normally capable of nodulating the roots of leguminous plants, and the failure of five EPS (extracellular polysaccharide)-deficient mutants to nodulate suggested that EPS is required for this nodulation. However, we report here that among a larger sample of mutants with altered EPS production, isolated from two species of Rhizobium (including one of the original set plus 34 new ones), production of EPS is not correlated with ability to nodulate appropriate hosts. Therefore, although involvement of a minor EPS component cannot be ruled out, there is no evidence that gross EPS is required for nodulation.