The rice seedling blight fungus Rhizopus microsporus has an unusual symbiosis with a bacterium, Burkholderia rhizoxinica, which lives within the fungal cytosol and produces a potent phytotoxin that causes severe losses in agriculture. To gain insight into symbiosis factors we investigated the endosymbiont's exopolysaccharide (EPS), a secreted matrix that plays pivotal roles in mediating cell-environment interactions. By a combination of homo- and heteronuclear 2D NMR experiments, we elucidated a previously unknown EPS structure: a repeating tetrasaccharide unit bearing a nonstoichiometric acetyl group on a mannose residue. We also analyzed the EPS biosynthesis gene cluster and generated a targeted mutant to compare the phenotypes. Scanning electron microscope images revealed a reduced ability of the mutant to form extracellular polymers around cell aggregates. Phylogenetic analyses suggest that the symbiont's EPS genes are retained through evolutionary processes.
Structure, Genetics and Function of an Exopolysaccharide by a Bacterium Living within Fungal Hyphae / Z., Uzum; Silipo, Alba; G., Lackner; DE FELICE, Antonia; Molinaro, Antonio; C., Hertweck. - In: CHEMBIOCHEM. - ISSN 1439-4227. - 16:3(2015), pp. 387-392. [10.1002/cbic.201402488]
Structure, Genetics and Function of an Exopolysaccharide by a Bacterium Living within Fungal Hyphae
SILIPO, ALBA;DE FELICE, ANTONIA;MOLINARO, ANTONIO;
2015
Abstract
The rice seedling blight fungus Rhizopus microsporus has an unusual symbiosis with a bacterium, Burkholderia rhizoxinica, which lives within the fungal cytosol and produces a potent phytotoxin that causes severe losses in agriculture. To gain insight into symbiosis factors we investigated the endosymbiont's exopolysaccharide (EPS), a secreted matrix that plays pivotal roles in mediating cell-environment interactions. By a combination of homo- and heteronuclear 2D NMR experiments, we elucidated a previously unknown EPS structure: a repeating tetrasaccharide unit bearing a nonstoichiometric acetyl group on a mannose residue. We also analyzed the EPS biosynthesis gene cluster and generated a targeted mutant to compare the phenotypes. Scanning electron microscope images revealed a reduced ability of the mutant to form extracellular polymers around cell aggregates. Phylogenetic analyses suggest that the symbiont's EPS genes are retained through evolutionary processes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.