Thromboelastometric Analysis of Anticancer Cerrena unicolor Subfractions Reveal Their Potential as Fibrin Glue Drug Carrier Enhancers.

In this study, the influence of two subfractions (with previously proven anti-cancer properties) isolated from wood rot fungus Cerrena unicolor on the formation of a fibrin clot was investigated in the context of potential use as fibrin glue and sealant enhancers and potential wound healing agents. With the use of ROTEM thromboelastometry, we demonstrated that, in the presence of fibrinogen and thrombin, the S6 fraction accelerated the formation of a fibrin clot, had a positive effect on its elasticity modulus, and enhanced the degree of fibrin cross-linking. The S5 fraction alone showed no influence on the fibrin coagulation process; however, in the presence of fibrin, it exhibited a decrease in anti-proliferative properties against the HT-29 line, while it increased the proliferation of cells in general at a concentration of 100 µg/mL. Both fractions retained their proapoptotic properties to a lesser degree. In combination with the S6 fraction in the ratio of 1:1 and 1:3, the fractions contributed to increased inhibition of the activity of matrix metalloproteinases (MMPs). This may suggest anti-metastatic activity of the combined fractions. In conclusion, the potential of the fractions isolated from the C. unicolor secretome to be used as a means of improving the wound healing process was presented. The potential for delivering agents with cytostatic properties introduced far from the site of action or exerting a pro-proliferative effect at the wound site with the aid of a fibrin sealant was demonstrated.

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

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 Zn2+ 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 Zn2+ 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 Zn2+ 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.

Surface Properties of Wild-Type Rhizobium leguminosarum bv. trifolii Strain 24.2 and Its Derivatives with Different Extracellular Polysaccharide Content.

Rhizobium leguminosarum bv. trifolii is a soil bacterium able to establish symbiosis with agriculturally important legumes, i.e., clover plants (Trifolium spp.). Cell surface properties of rhizobia play an essential role in their interaction with both biotic and abiotic surfaces. Physicochemical properties of bacterial cells are underpinned by the chemical composition of their envelope surrounding the cells, and depend on various environmental conditions. In this study, we performed a comprehensive characterization of cell surface properties of a wild-type R. leguminosarum bv. trifolii strain 24.2 and its derivatives producing various levels of exopolysaccharide (EPS), namely, pssA mutant Rt5819 deficient in EPS synthesis, rosR mutant Rt2472 producing diminished amounts of this polysaccharide, and two EPS-overproducing strains, Rt24.2(pBA1) and Rt24.2(pBR1), under different growth conditions (medium type, bacterial culture age, cell viability, and pH). We established that EPS plays an essential role in the electrophoretic mobility of rhizobial cells, and that higher amounts of EPS produced resulted in greater negative electrophoretic mobility and higher acidity (lower pKapp,av) of the bacterial cell surface. From the tested strains, the electrophoretic mobility was lowest in EPS-deficient pssA mutant. Moreover, EPS produced by rhizobial strains resulted not only in an increase of negative surface charge but also in increased hydrophobicity of bacterial cell surface. This was determined by measurements of water contact angle, surface free energy, and free energy of bacterial surface-water-bacterial surface interaction. Electrophoretic mobility of the studied strains was also affected by the structure of the bacterial population (i.e., live/dead cell ratio), medium composition (ionic strength and mono- and divalent cation concentrations), and pH.