Endophytic fungi of Paullinia cupana and its antimicrobial potential.

The objective of this study is to characterize P. cupana endophytic fungi and evaluate their antibiotic potential by agar diffusion test. Fruits and root fragments from 6 individuals were collected and sterilized with 70% ethanol and 2% sodium hypochlorite

Basal-plane Incommensurate Phases in HCP Structures

An Ising model with competing interaction is used to study the appearance of incommensurate phases in the basal plane of an hexagonal closed-packed structure. The calculated mean-field phase diagram reveals various 1q-incommensurate and lock-in phases. The results are applied to explain the basal-plane incommensurate phase in some compounds of the A'A"BX_4 family, like K_2MoO_4, K_2WO_4, Rb_2WO4 and to describe the sequence of high-temperature phase transitions in other compounds of this family.Comment: 8 pages, RevTeX + 4 ps figure

Resistante to mercury of endophytic bacteria obtained in contaminated sites.

Strategies for remediation of soils contaminated with mercury (Hg) are important and necessary. Several bacterial species interfere with biogeochemical cycle of mercury and are potential tools in bioremediation and/or phytoremediation programs. These bacteria are resistant to mercury and the main mechanism of resistance is mediated by proteins codificated by operon mer. This study aims to determine the level of resistance to mercury of endophytic bacteria and detect the presence of merA gene

A tight-binding potential for atomistic simulations of carbon interacting with transition metals: Application to the Ni-C system

We present a tight-binding potential for transition metals, carbon, and transition metal carbides, which has been optimized through a systematic fitting procedure. A minimal basis, including the s, p electrons of carbon and the d electrons of the transition metal, is used to obtain a transferable tight-binding model of the carbon-carbon, metal-metal and metal-carbon interactions applicable to binary systems. The Ni-C system is more specifically discussed. The successful validation of the potential for different atomic configurations indicates a good transferability of the model and makes it a good choice for atomistic simulations sampling a large configuration space. This approach appears to be very efficient to describe interactions in systems containing carbon and transition metal elements

Endophytic bacterium isolated of hosts present in contaminated areas by mercury in Pantanal mato-grossense.

The mercury is a contaminant in gold mining in the city of Poconé. This heavy metal is a toxic in different organisms and affect the human by bioaccumulation process causing a serie of cronic diseases. Mercury can be easily absorbed by plants and be accumulated in the human body through the food chain. The hypothesis is microorganism that is in association with plants, that survive in contaminated areas with mercury, provide greater resistance to contaminant and possibly an increased frequency of colonization. In this way, the aim of this study was to isolate endophytic bacterium that exhibit resistance to mercury

Isolation of endophytic fungi in environments with and without traces of mercury contamination, Pantanal of Mato Grosso.

The mining activity in Mato Grosso is an economic source for many cities, especially in Poconé, where this activity is responsible for significant change in the landscape and the contamination of the ecosystem by mercury. This results in serious damage to biota enhanced by bioaccumulation capacity. Mercury is toxic to all organisms, however, some microorganisms have innate or acquired tolerance to metal. Therefore, our hypothesis is based on the premise that plants in contaminated environments with mercury harbor a specific community of endophytic fungi, therefore, variations in the colonization frequency of the endophytes in these plants are expected, when compared to places without contamination

Antibiosis of actinomycetes from Paullina cupana var. sorbilis (mart.) Ducke against fungi pathogenic.

Guarana (Paullinia cupana var. Sorbilis (Mart.) Ducke) is a native species of economic and social importance in Brazil serving the domestic and international demands. This culture is attacked by Colletotrichum guaranicola Albuq. and Fusarium decencellulare Brick, causal agents of anthracnose and overbudding, respectively. Actinomycetes are bacteria that may produce secondary metabolites with antibacterial and antifungal potential. The isolation of endophytic with antibiosis agaist pathogenic fungi is the first step in biological control and bioprospecting antimicrobial compounds programs

Capacity resistance of endophytic fungi the mercury.

Contamination of biological systems by mercury represents a global concern, given the difficulty of degradation, persistence and potential toxicity of this metal in the environment. Remediation strategies of soils contaminated with mercury are required and the use of microorganisms as bioremediation agents is fully justified, in particular, the various mechanisms of tolerance to heavy metals allocated to them, particularly for fungi arising from various chemical processes, such as transformation valence, intra and extracellular precipitation and oxidation. Our hypothesis is that endophytic fungi isolated from areas contaminated by mercury present higher resistance to this metal

Microbiol diversity in rhizosphere resistant and susceptible guarana collected in Maués and Manaus.

The rhizosphere is the soil region subject to influence of exudates released by plants and microorganisms (epiphytic and endophytic). In addition, this region has large variety of bacteria that can contribute to plant growth and/or inhibiting the activity of plant pathogens. The culture of guarana (Paullinia cupana var. Sorbilis (Mart.) Ducke) is threatened by the presence of the fungus Colletotrichum guaranicola Albuq. and Fusarium decencellulare Brick, causal agents of anthracnose and overbudding, respectively. In this work, the metabolic diversity of rhizospheric bacteria was studied in resistant (R) and susceptible (S) clones collected in Manaus (Mn) and Maués (Mu)

Structure and relaxations in liquid and amorphous Selenium

We report a molecular dynamics simulation of selenium, described by a three-body interaction. The temperatures T_g and T_c and the structural properties are in agreement with experiment. The mean nearest neighbor coordination number is 2.1. A small pre-peak at about 1 AA^-1 can be explained in terms of void correlations. In the intermediate self-scattering function, i.e. the density fluctuation correlation, classical behavior, alpha- and beta-regimes, is found. We also observe the plateau in the beta-regime below T_g. In a second step, we investigated the heterogeneous and/or homogeneous behavior of the relaxations. At both short and long times the relaxations are homogeneous (or weakly heterogeneous). In the intermediate time scale, lowering the temperature increases the heterogeneity. We connect these different domains to the vibrational (ballistic), beta- and alpha-regimes. We have also shown that the increase in heterogeneity can be understood in terms of relaxations