Biological activity of silver nanoparticles synthesized with Paenibacillus polymyxa exopolysaccharides.

Recently, there has been increased interest in the synthesis of nanoparticles by using natural polysaccharides. These polysaccharides are eco-friendly, nontoxic, and cheap to prepare. On the other hand, the attention in hydrocolloids and films has significantly enhanced, and their application is very promising in the food, pharmaceutical, perfumery and cosmetics, oil, paper, and textile industries. In this context, the present study is aimed to prepare silver nanoparticles by using viscous and superviscous exopolysaccharides of the rhizobacterium Paenibacillus polymyxa strains, CCM 1465 and 88A, and examined the properties of the resultant nanoparticles. We examined the synthesis and properties of silver nanoparticles under variable synthetic conditions by using exopolysaccharides of the rhizobacteria Paenibacillus polymyxa CCM 1465 and 88A. To prepare nanoparticles, we used different combinations of exopolysaccharide and silver nitrate concentrations: 1-10 mg/mL and 1-40 mM, respectively. The resulting solutions were alkalinized from pH 7.5-12 and heated for 15, 30, and 60 min to determine the optimal synthetic conditions. We found that the exopolysaccharides of strains CCM 1465 and 88A reduced silver ions and acted as nanoparticle stabilizers. The prepared spherical, oval, and triangular particles were stable and ranged in size from 2 to 40 nm, depending on the strain and on the experimental conditions. The nanoparticles showed antibacterial and antifungal activity against Escherichia coli K-12, Pseudomonas aeruginosa 50.3, Bacillus subtilis 26-D, and Fusarium oxysporum. In addition, the nanoparticles were active against SK-MEL-2 human melanoma cells. This finding shows the promise of further research on the exopolysaccharides of P. polymyxa 1465 and 88А in different fields of science, including medicine.

Effect of exopolysaccharides of Paenibacillus polymyxa rhizobacteria on physiological and morphological variables of wheat seedlings.

Paenibacillus polymyxa is a promising plant-growth-promoting rhizobacterium that associates with a wide range of host plants, including agronomically important ones. Inoculation of wheat seedlings with P. polymyxa strains CCM 1465 and 92 was found to increase the mitotic index of the root cells 1.2- and 1.6-fold, respectively. Treatment of seedlings with the exopolysaccharides (EPSs) of these strains increased the mitotic index 1.9-fold (P. polymyxa CCM 1465) and 2.8-fold (P. polymyxa 92). These increases indicate activation of cell division in the root meristems. Analysis of the morphometric variables of the seedlings showed that P. polymyxa CCM 1465, P. polymyxa 92, and their EPSs promoted wheat growth, increasing root and shoot length up to 22% and root and shoot dry weight up to 28%, as compared with the control. In addition, both strains were found to intensely colonize the seedling root surface. Thus, P. polymyxa EPSs are active metabolites that, along with whole cells, are responsible for the contact interactions of the bacteria with wheat roots and are implicated in the induction of plant responses to these interactions. The strains used in this work are of interest for further study to broaden the existing understanding of the mechanisms of plant-bacterial interactions and to develop effective biofertilizers for agricultural purposes.

Isolation, structure, and potential biotechnological applications of the exopolysaccharide from Paenibacillus polymyxa 92.

Paenibacillus polymyxa 92, isolated from wheat roots, produced large amounts (38.4 g L-1) of exopolysaccharide (EPS) in a liquid nutrient medium containing 10 % (w/v) sucrose. The EPS was precipitated from the culture broth with cold acetone and was purified by gel filtration and anion-exchange chromatography. The molecular mass of the EPS was 2.29-1.10 × 105 Da. Diffuse reflectance infrared Fourier transform and nuclear magnetic resonance spectra showed that the EPS was a linear ß-(2→6)-linked fructan (levan). Aqueous EPS solutions showed pseudoplastic behavior when shear stress was applied at different temperatures. By using the Ostwald-de Waele model, the rheological characteristics of the EPS solution were ascertained. The sorption capacity of the EPS for Zn(II), Cd(II), Pb(II), and Cu(II) was investigated. Sorption was maximal (q = 481 mg g-1) for Cu(II) ions. In model experiments, treatment of wheat seeds with EPS solution significantly increased the length of seedling roots and shoots.

Immunomodulatory activity of exopolysaccharide from the rhizobacterium Paenibacillus polymyxa CCM 1465.

Bacterial polysaccharides are promising stimulants of protective functions in humans and animals. We investigated the ability of exopolysaccharide from the rhizobacterium Paenibacillus polymyxa CCM 1465 to induce nonspecific resistance factors in the macroorganism. We examined in vitro the effect of the exopolysaccharide, produced with different carbon sources, on the phagocytic activity of murine macrophages, on the generation of reactive oxygen species and of enzymes (acid phosphatase and myeloperoxidase), on the proliferation of murine splenocytes, and on the synthesis of proinflammatory cytokines [interleukin-1 (IL-1) and tumor necrosis factor α (TNF-α)] by human mononuclear cells. The exopolysaccharide promoted the phagocytosis of bacterial cells, activated metabolic processes in human and animal leukocytes, and moderately affected the production of TNF-α and IL-1ß. The exopolysaccharides produced on media with glucose and sucrose differed in their effect on the immune cells, possibly owing to their different compositions, structures, and properties. The results validly indicate that the exopolysaccharide of P. polymyxa CCM 1465 promotes nonspecific immunity. Therefore, it can find application as a biologically active immunomodulatory substance.

Assessing the efficacy of co-inoculation of wheat seedlings with the associative bacteria Paenibacillus polymyxa 1465 and Azospirillum brasilense Sp245.

Co-inoculation of associative bacteria, which have high nitrogen-fixing activity, tolerance for environmental conditions, and the ability to compete with the natural microflora, is used widely to enhance the growth and yields of agricultural plants. We evaluated the ability of 2 co-inoculated plant-growth-promoting rhizobacteria, Paenibacillus polymyxa 1465 and Azospirillum brasilense Sp245, to colonize roots of wheat (Triticum aestivum L. 'Saratovskaya 29') seedlings, and we assessed the morphometric parameters of wheat early in its development. Analysis by ELISA with polyclonal antibodies raised against the exopolysaccharide of P. polymyxa 1465 and the lipopolysaccharide of A. brasilense Sp245 demonstrated that the root-colonizing activity of A. brasilense was higher when the bacterium was co-inoculated with P. polymyxa than when it was inoculated singly. Immunofluorescence microscopy with Alexa Fluor 532-labeled antibodies revealed sites of attachment of co-inoculated P. polymyxa and A. brasilense and showed that the 2 bacteria colonized similar regions of the roots. Co-inoculation exerted a negative effect on wheat seedling development, inhibiting root length by 17.6%, total root weight by 11%, and total shoot weight by 12%. Under certain conditions, dual inoculation of wheat may prove ineffective, apparently owing to the competition between the rhizobacteria for colonization sites on the plant roots. The findings from this study may aid in developing techniques for mixed bacterial inoculation of cultivated plants.

Paenibacillus polymyxa rhizobacteria and their synthesized exoglycans in interaction with wheat roots: colonization and root hair deformation.

We examined the ability of several Paenibacillus polymyxa strains to colonize wheat roots and the ability of P. polymyxa exoglycans to induce root hair deformation. For the first time, exopolysaccharides isolated from P. polymyxa were found to produce, with different intensities, various morphological changes in the root hairs of wheat seedlings, which are some of the earliest responses of plants to bacteria in the surrounding milieu. P. polymyxa 1465, giving the highest exopolysaccharide yield and the highest viscosity of aqueous exopolysaccharide solutions, was best able to colonize wheat seedling roots, and its exopolysaccharide proved to be the best in producing root hair deformation. It is suggested that P. polymyxa exoglycans have an active role in the establishment of plant-microbe associations.

Biofilm formation by Paenibacillus polymyxa strains differing in the production and rheological properties of their exopolysaccharides.

We evaluated the ability of several strains of the rhizobacterium Paenibacillus polymyxa, differing in the yield and rheological properties of their exopolysaccharides, to form biofilms on abiotic surfaces. Of these strains, P. polymyxa 1465, giving the highest yield of extracellular polysaccharides and the highest kinematic viscosity of the culture liquid and of aqueous polysaccharide solutions, proved to be the most active in forming biofilms on hydrophobic and hydrophilic surfaces. Enzyme-linked immunosorbent assay with rabbit polyclonal antibodies developed to isolated exopolysaccharides of P. polymyxa 1465 and 92 was used to detect P. polymyxa's polysaccharidic determinants in the composition of the biofilm materials.

Use of ELISA with antiexopolysaccharide antibodies to evaluate wheat-root colonization by the rhizobacterium Paenibacillus polymyxa.

Enzyme-linked immunosorbent assay with rabbit polyclonal antibodies developed to isolated exopolysaccharide of Paenibacillus polymyxa 1465 was used to evaluate the colonization of wheat-seedling roots by this bacterium. The assay conditions were optimized for detection of the P. polymyxa exopolysaccharide determinants forming part of the samples used (homogenates of inoculated roots). The dynamics of the immunoenzymatic revealing of specific polysaccharidic antigenic determinants in the samples' composition correlated with an increase in P. polymyxa numbers on the roots found by estimation of colony-forming units.