Extracellular polysaccharide protects Rhizobium leguminosarum cells against zinc stress in vitro and during symbiosis with clover

Abstract

Rhizobium leguminosarum bv. trifolii is a soil bacterium that establishes symbiosis with clover (Trifolium spp.) under nitrogen-limited conditions. This microorganism produces exopolysaccharide (EPS), which plays an important role in symbiotic interactions with the host plant. The aim of the current study was to establish the role of EPS in the response of R. leguminosarum bv. trifolii cells, free-living and during symbiosis, to zinc stress. We show that EPS-deficient mutants were more sensitive to Zn exposure than EPS-producing strains, and that EPS overexpression conferred some protection onto the strains beyond that observed in the wild type. Exposure of the bacteria to Zn ions stimulated EPS and biofilm production, and increased cell hydrophobicity. However, zinc stress negatively affected the motility and attachment of bacteria to clover roots, as well as the symbiosis with the host plant. In the presence of Zn ions, cell viability, root attachment, biofilm formation and symbiotic efficiency of EPS-overproducing strains were significantly higher than those of the EPS-deficient mutants. We conclude that EPS plays an important role in the adaptation of rhizobia to zinc stress, in both the free-living stage and during symbiosis.

The Lichens’ Microbiota, Still a Mystery?

“…Besides creating anaerobic niches, EPS and thus biofilm formation may play a role in the protection against pH and metals as shown for Rhizobium leguminosarum, a soil bacterium that establishes symbiosis with Trifolium spp. (Kopycińska et al, 2018).…”

Effects of Cadmium Stress on Physiological Indexes and Fruiting Body Nutritions of Agaricus Brasiliensis

“…Extracellular polysaccharides play a role in the response, free survival and symbiosis of legume rhizobia to zinc stress. Zinc stress can stimulate the synthesis of extracellular polysaccharide and effectively protect cells from zinc stress 44 The increase in isoleucine, phenylalanine and tyrosine under combined Cd and N stress may be because they are both glucogenic and ketogenic amino acids, while proline, histidine, glutamine, valine and asparagine on the other hand are glucogenic amino acids. The nature of the different amino acids and their possible roles in lipid and carbohydrate biosynthesis through the tricarboxylic acid cycle (TCA cycle) can explain the positive relationship they had with total lipid and carbohydrates production in C.…”

Tolerance mechanism of Trichoderma asperellum to Pb2+: response changes of related active ingredients under Pb2+ stress

“…The zinc stress can stimulate extracellular polysaccharide synthesis and it effectively protected the cells to against the zinc stress. 39 The polysaccharides can provide more adsorption sites for Pb 2+ and reduce the toxicity of Pb 2+ on cells.…”