2 research outputs found
Metabolism of multiple glycosaminoglycans by <i>Bacteroides thetaiotaomicron</i> is orchestrated by a versatile core genetic locus
The human gut microbiota (HGM), which is critical to human health, utilises complex glycans as its major carbon source. Glycosaminoglycans represent an important, high priority, nutrient source for the HGM. Pathways for the metabolism of various glycosaminoglycan substrates remain ill-defined. Here we perform a biochemical, genetic and structural dissection of the genetic loci that orchestrates glycosaminoglycan metabolism in the organism Bacteroides thetaiotaomicron. Here, we report: the discovery of two previously unknown surface glycan binding proteins which facilitate glycosaminoglycan import into the periplasm; distinct kinetic and genetic specificities of various periplasmic lyases which dictate glycosaminoglycan metabolic pathways; understanding of endo sulfatase activity questioning the paradigm of how the âsulfation problemâ is handled by the HGM; and 3D crystal structures of the polysaccharide utilisation loci encoded sulfatases. Together with comparative genomic studies, our study fills major gaps in our knowledge of glycosaminoglycan metabolism by the HGM
Modulation of immune responses by targeting CD169/Siglec-1 with the glycan ligand
A fundamental role in the plant-bacterium interaction for
Gram-negative phytopathogenic bacteria is played by membrane
constituents, such as proteins, lipopoly- or lipooligosaccharides
(LPS, LOS) and Capsule Polysaccharides (CPS).
In the frame of the understanding the molecular basis of plant bacterium interaction, the Gram-negative bacterium Agrobacterium vitis was selected in this study. It is a phytopathogenic member of the Rhizobiaceae family and it induces the crown gall disease selectively on grapevines (Vitis vinifera).
A. vitis wild type strain F2/5, and its mutant in the quorum
sensing gene ÎaviR, were studied. The wild type produces biosurfactants; it is considered a model to study surface motility, and it causes necrosis on grapevine roots and HR (Hypersensitive
Response) on tobacco. Conversely, the mutant does not show any
surface motility and does not produce any surfactant material;
additionally, it induces neither necrosis on grape, nor HR on
tobacco. Therefore, the two strains were analyzed to shed some
light on the QS regulation of LOS structure and the consequent
variation, if any, on HR response. LOS from both strains were isolated and characterized: the two LOS structures maintained several common features and differed for few others.
With regards to the common patterns, firstly: the Lipid A region
was not phosphorylated at C4 of the non reducing glucosamine
but glycosylated by an uronic acid (GalA) unit, secondly: a third
Kdo and the rare Dha (3-deoxy-lyxo-2-heptulosaric acid) moiety
was present.
Importantly, the third Kdo and the Dha residues were substituted
by rhamnose in a not stoichiometric fashion, giving four different
oligosaccharide species.
The proportions among these four species, is the key difference
between the LOSs from both the two bacteria.
LOS from both strains and Lipid A from wild type A. vitis are
now examined for their HR potential in tobacco leaves and grapevine roots