A broad variety of bacteria including the Rhizobiaceae are able to secrete polysaccharides. Sugar polymers that form an adherent cohesive layer on the cell surface are designated capsular polysacharides (CPS), whereas the term exopolysaccharide (EPS) is used for polysaccharides with little or no cell association. Due to the variation of monosaccharide sequences, condensation linkages and non-carbohydrate decorations, an infinite array of structures can be provided by this class of macromolecules. Different rheological properties depend on the structure and the molecular weight of EPS. These properties and the location of EPS, forming the outer layer of the cell surface, contribute to the cell protection against environmental influences, attachment to surfaces, nutrient gathering and to antigenicity (Costerton et al., 1987, Sutherland 1988, Whitfield 1988, Beveridge and Graham 1991). The structural diversity of oligosaccharides derived from EPS enables them to function additionally as informational molecules in cell-cell-communications. Finally, many symbiotic bacteria of the Rhizobiaceae use oligosaccharides as signal molecules in the interaction with their host plant.

glycosyl transferase, Indeterminate Nodule, Symbiotic Phenotype, Exopolysaccharide Biosynthesis, SU47 Mutant

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]O[C@@H]1[C@@H](O)[C@H](O[C@@H]2[C@@H](O)[C@H](C)O[C@H](O[C@H]3[C@H](C)O[C@H](O[C@H]4[C@H](C)O[C@@H]([*])[C@H](O)[C@@H]4O)[C@H](O[C@@H]4O[C@H](C(=O)O)[C@@H](O)[C@H](O)[C@H]4OC)[C@@H]3O)[C@@H]2O)O[C@H](CO)[C@@H]1O

790.718 g/mol (C₃₁H₅₀R₂O₂₃, R = next and previous repeats, not counted in mol weight)

Mushrooms are widely distributed around the world and are heavily consumed because of their nutritional value and medicinal properties. Polysaccharides (PSs) are an important component of mushrooms, a major factor in their bioactive properties, and have been intensively studied during the past two decades. Monosaccharide composition/combinations are important determinants of PS bioactivities. This review summarizes: (i) monosaccharide composition/combinations in various mushroom PSs, and their relationships with PS bioactivities; (ii) possible biosynthetic pathways of mushroom PSs and effects of key enzymes on monosaccharide composition; (iii) regulation strategies in PS biosynthesis, and prospects for controllable biosynthesis of PSs with enhanced bioactivities.

biosynthesis, regulation, structure-activity relationship, Monosaccharide composition, bioactivity, mushroom polysaccharides

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]O[C@H]1[C@@H](OC[C@H]2O[C@H](OC[C@H]3O[C@H]([*])[C@H](O[C@H]4O[C@H](CO)[C@@H](O)[C@H](O)[C@H]4O)[C@@H](O)[C@@H]3O)[C@H](O)[C@@H](O[C@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@H]3O)[C@H]2O)O[C@@H](C)[C@H](O)[C@H]1O

794.706 g/mol (C₃₀H₅₀R₂O₂₄, R = next and previous repeats, not counted in mol weight)

Rhizobia are Gram-negative bacteria that can exist either as free-living bacteria or as nitrogen-fixing symbionts inside root nodules of leguminous plants. The composition of the rhizobial outer surface, containing a variety of polysaccharides, plays a significant role in the adaptation of these bacteria in both habitats. Among rhizobial polymers, exopolysaccharide (EPS) is indispensable for the invasion of a great majority of host plants which form indeterminate-type nodules. Various functions are ascribed to this heteropolymer, including protection against environmental stress and host defense, attachment to abiotic and biotic surfaces, and in signaling. The synthesis of EPS in rhizobia is a multi-step process regulated by several proteins at both transcriptional and post-transcriptional levels. Also, some environmental factors (carbon source, nitrogen and phosphate starvation, flavonoids) and stress conditions (osmolarity, ionic strength) affect EPS production. This paper discusses the recent data concerning the function of the genes required for EPS synthesis and the regulation of this process by several environmental signals. Up till now, the synthesis of rhizobial EPS has been best studied in two species, Sinorhizobium meliloti and Rhizobium leguminosarum. The latest data indicate that EPS synthesis in rhizobia undergoes very complex hierarchical regulation, in which proteins engaged in quorum sensing and the regulation of motility genes also participate. This finding enables a better understanding of the complex processes occurring in the rhizosphere which are crucial for successful colonization and infection of host plant roots.

Rhizobium leguminosarum, Sinorhizobium meliloti, exopolysaccharide synthesis, motility, quorum sensing, exo and pss genes, rhizobium-legume symbiosis

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]O[C@@H]1[C@@H](O)[C@H](O[C@@H]2[C@@H](O)[C@H](C)O[C@H](O[C@H]3[C@H](C)O[C@H](O[C@H]4[C@H](C)O[C@@H]([*])[C@H](O)[C@@H]4O)[C@H](O[C@@H]4O[C@H](C(=O)O)[C@@H](O)[C@H](O)[C@H]4OC)[C@@H]3O)[C@@H]2O)O[C@H](CO)[C@@H]1O

790.718 g/mol (C₃₁H₅₀R₂O₂₃, R = next and previous repeats, not counted in mol weight)

Ganoderma lucidum (G. lucidum) is a mushroom which has been used for health promotion for a long time in China. In the present work a neutral hetero-polysaccharide, named FYGL-1, was isolated from FYGL which was reported previously capable of antihyperglycemia in vivo for further detailed chemical structure investigation. The results of monosaccharide composition and GPC analysis indicated that FYGL-1 consisted of galactose, rhamnose and glucose in mole ratio of 1.00:1.15:3.22 with a molecular weight of 78 kDa. The detailed structure of FYGL-1 was characterized by periodate oxidation, Smith degradation, methylation analysis, along with FT-IR, GC, GC–MS, 1D 1H and 13C NMR and 2D NMR (HSQC, COSY, NOESY and TOCSY). Based on the analysis of the results, the structure of the repeating unit of FYGL-1 was established as structure.

polysaccharide, NMR spectroscopy, structure characterization, Ganoderma lucidum

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
6,6	bLRhap	102.20	73.55	72.91	65.58	?	17.69
6,3	aDGlcp
6	aDGalp
2	aDGlcp
	aDGlcp


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
6,6	bLRhap	4.48	3.35	3.50	3.72	3.77	1.24
6,3	aDGlcp
6	aDGalp
2	aDGlcp
	aDGlcp


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
6,6	bLRhap	102.20/4.48	73.55/3.35	72.91/3.50	65.58/3.72	?/3.77	17.69/1.24
6,3	aDGlcp
6	aDGalp
2	aDGlcp
	aDGlcp

The spectrum also has 1 signal at unknown position (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]O[C@H]1[C@@H](OC[C@H]2O[C@H](OC[C@H]3O[C@H]([*])[C@H](O[C@H]4O[C@H](CO)[C@@H](O)[C@H](O)[C@H]4O)[C@@H](O)[C@@H]3O)[C@H](O)[C@@H](O[C@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@H]3O)[C@H]2O)O[C@@H](C)[C@H](O)[C@H]1O

794.706 g/mol (C₃₀H₅₀R₂O₂₄, R = next and previous repeats, not counted in mol weight)