Induction of Isochromanones by Co-Cultivation of the Marine Fungus Cosmospora sp. and the Phytopathogen Magnaporthe oryzae

Microbial co-cultivation is a promising approach for the activation of biosynthetic gene clusters (BGCs) that remain transcriptionally silent under artificial culture conditions. As part of our project aiming at the discovery of marine-derived fungal agrochemicals, we previously used four phytopathogens as model competitors in the co-cultivation of 21 marine fungal strains. Based on comparative untargeted metabolomics analyses and anti-phytopathogenic activities of the co-cultures, we selected the co-culture of marine Cosmospora sp. with the phytopathogen Magnaporthe oryzae for in-depth chemical studies. UPLC-MS/MS-based molecular networking (MN) of the co-culture extract revealed an enhanced diversity of compounds in several molecular families, including isochromanones, specifically induced in the co-culture. Large scale co-cultivation of Cosmospora sp. and M. oryzae resulted in the isolation of five isochromanones from the whole co-culture extract, namely the known soudanones A, E, D (1-3) and their two new derivatives, soudanones H-I (4-5), the known isochromans, pseudoanguillosporins A and B (6, 7), naphtho-γ-pyrones, cephalochromin and ustilaginoidin G (8, 9), and ergosterol (10). Their structures were established by NMR, HR-ESIMS, FT-IR, electronic circular dichroism (ECD) spectroscopy, polarimetry ([α]D), and Mosher’s ester reaction. Bioactivity assays revealed antimicrobial activity of compounds 2 and 3 against the phytopathogens M. oryzae and Phytophthora infestans, while pseudoanguillosporin A (6) showed the broadest and strongest anti-phytopathogenic activity against Pseudomonas syringae, Xanthomonas campestris, M. oryzae and P. infestans. This is the first study assessing the anti-phytopathogenic activities of soudanones

Graphene oxide toxicological effects on daphnia and hydra.

The increased use of nanomaterials products requires robust strategies to identify risks when they are released into the environment. Graphene and its derivatives are promising candidates for biomedical applications and as potential advanced water purification agents. However, little is known about their ecotoxicological risks. Aquatic toxicity tests are performed with different aquatic organisms as daphnia and hydra in order to evaluate the risks resulting from the presence of graphene oxide (GO) in the environment. The following GO concentrations were tested: 0, 1, 10 and 100 mg.L-1. Acute toxicity to D. magna was evaluated in a period of 48 hours when was recorded the number of moving subjects in order to determine the CE5024h and CE5048h (n = 24 / group). The percentage of daphnia presenting mobility after 48 hours of exposure was greater than 60% in all groups. There was a concentration effect of graphene oxide (p = 0.02) and mobility was 20% lower in group exposed to 100 mg.L-1 than the control group. To evaluate the occurrence of the effect of sublethal concentrations for 96 h, it was evaluate neonate D. similis growth rate through exposure to the same conditions used for acute toxicity testing (n = 10 / group). The bodies were photographed at the start of the test and every 24 hours. Also, there was studied the effect of the organisms mobility during 96 hours calculating the median survival time of the population, defined as the average time between the start of exposure and the immobility of organisms. There was a sharp decline when the organisms were subjected to 100 mg. L-1 GO. The Hydra attenuata test was performed for 96h. The organisms were observed every 24 hours for the presence of changes ranging from tentacles with bulbs (low toxicity) till shortening of the tentacles (severe toxicity), tulip aspect and disintegration (lethal). A mean score for each concentration was calculated. No mortality was observed in any concentration tested. However, it was observed some morphological alterations after 72h of 100.0 mg.L-1 exposure as clubbed and shortened tentacles and body slightly contracted. Exposures of the test organisms indicate that GO do not present a lethal risk or adversely affect them at concentrations lower to 10.0 mg. L-1. Even though the results apparently demonstrate that GO currently do not pose a serious risk, it may exert some damage in aquatic organisms tested at higher doses

Effects of graphene oxide on aquatic macrophyte under the influence of humic substances.

The behavior of nanostructured graphene oxide (GO) in the environment is complex and must be completely understood to evaluate the risk involved. Studies show that humic acid (HA) can stabilize nanomaterials in water and change its behavior. The aquatic macrophyte duckweed (Lemna minor) is a good plant model for adverse effects evaluation of many test-materials due to its fast growth and small size. This study assessed the effect of GO, with and without HA, on the growth of L. minor on fronds number and biomass changes. The plants were exposed during 7 days to the nominal concentrations of GO equals to 0.0 (control), 0.1, 1.0, 10.0 and 100.0 mg L-1, in the absence or in the presence of 20 mg L-1 of HA. Tests were conducted in multiwell polystyreneplates where each well contained two fronds at the start of the experiment. The number of replicates for each test?concentration was 24 wells. The plants were exposed to a constant photoperiod (24:0, light:dark cycle) supplied by white fluorescent lamps (~700 lux) at the temperature of 20± 2 ºC. The fronds number was counted daily and the wet weight was assessed at the end of the experiment. The concentration that promoted 50% of inhibition in the growth rate in terms of fronds number (EC50-7d growth) and the concentration that promoted 50% of wet weight reduction (EC50-7d biomass) were calculated. The reduction of the growth rate by GO at the concentration of 100 mg L-1 was remarkable detected (P 100 mg L-1. This value attributes a practically non-toxicity for the test-material in terms of fronds production. On the other hand, the calculated EC50-7d biomass for the GO in the presence of HA or not was 2.8 and 2.4 mg L-1 respectively. These results indicate that the adverse effects of GO in L. minor are more pronounced on the biomass production since it was clearly observed that reductions in the fronds sizes were greater than in the fronds number. The EC50-7d biomass values assigns a moderate toxicity of GO to L. minor and these data may be useful for the establishment of maximum concentrations limits of this material in water bodies

Efeitos da exposição aguda ao dimetoato em microcrustáceos e anelídeos.

Resumo: O dimetoato é um inseticida organofosforado de amplo espectro que penetra no corpo através da ingestão, inalação e contato com a pele. Em animais, pode ser metabolizado em produtos de oxidação mais tóxicos afetando muitos organismos não-alvo, incluindo invertebrados aquáticos e do solo. Tanto o microcrustáceo Daphnia magna quanto a minhoca Eisenia fetida são organismos adequados para ensaios de toxicidade, uma vez que pode ser facilmente criados e possuem curto ciclo de vida. O objetivo desse estudo foi avaliar a toxicidade aguda (48h) do dimetoato no microcrustáceo Daphnia magna enquanto organismo-teste aquático e avaliar os efeitos do dimetoato grau técnico sobre a sobrevivência de Eisenia fetida. Procurou-se também verificar a viabilidade do método de contato com papel de filtro para avaliação de ensaios de toxicidade aguda com minhocas. A CE50 para Daphnia magna foi de 0,99 mg/L com intervalo de confiança 95% de 1,22 - 1,54. A CL50 foi de 1083,55 mg/L de dimetoato grau técnico com limites inferiores e superiores a 95% de 711,23 ? 1375,55 mg/L para a E. fetida. O dimetoato grau técnico apenas apresentou letalidade a 50% da população em concentração acima de 1000 mg/L o que pode ser considerado praticamente não tóxico a organismos não-alvo do solo. Foi evidenciada também a eficiência do método de contato com papel de filtro como ferramenta para avaliação de toxicidade para E. fetida.bitstream/item/138620/1/2015AA061.pd

Semiclassical analysis of the quantum interference corrections to the conductance of mesoscopic systems

The Kubo formula for the conductance of a mesoscopic system is analyzed semiclassically, yielding simple expressions for both weak localization and universal conductance fluctuations. In contrast to earlier work which dealt with times shorter than $O(\log \hbar^{-1})$, here longer times are taken to give the dominant contributions. For such long times, many distinct classical orbits may obey essentially the same initial and final conditions on positions and momenta, and the interference between pairs of such orbits is analyzed. Application to a chain of $k$ classically ergodic scatterers connected in series gives the following results: $-{1 \over 3} [ 1 - (k+1)^{-2} ]$ for the weak localization correction to the zero--temperature dimensionless conductance, and ${2 \over 15} [ 1 - (k+1)^{-4} ]$ for the variance of its fluctuations. These results interpolate between the well known ones of random scattering matrices for $k=1$, and those of the one--dimensional diffusive wire for $k \rightarrow \infty$.Comment: 53 pages, using RevTeX, plus 3 postscript figures mailed separately. A short version of this work is available as cond-mat/950207

Systematic Analytical Approach to Correlation Functions of Resonances in Quantum Chaotic Scattering

We solve the problem of resonance statistics in systems with broken time-reversal invariance by deriving the joint probability density of all resonances in the framework of a random matrix approach and calculating explicitly all n-point correlation functions in the complex plane. As a by-product, we establish the Ginibre-like statistics of resonances for many open channels. Our method is a combination of Itzykson-Zuber integration and a variant of nonlinear $\sigma-$model and can be applied when the use of orthogonal polynomials is problematic.Comment: 4 pages, no figures. Misprints corrected, some details on single-channel and many-channel cases are adde

A Diagrammatic Theory of Random Scattering Matrices for Normal-Superconducting Mesoscopic Junctions

The planar-diagrammatic technique of large-$N$ random matrices is extended to evaluate averages over the circular ensemble of unitary matrices. It is then applied to study transport through a disordered metallic ``grain'', attached through ideal leads to a normal electrode and to a superconducting electrode. The latter enforces boundary conditions which coherently couple electrons and holes at the Fermi energy through Andreev scattering. Consequently, the {\it leading order} of the conductance is altered, and thus changes much larger than $e^2/h$ are observed when, e.g., a weak magnetic field is applied. This is in agreement with existing theories. The approach developed here is intermediate between the theory of dirty superconductors (the Usadel equations) and the random-matrix approach involving transmission eigenvalues (e.g. the DMPK equation) in the following sense: even though one starts from a scattering formalism, a quantity analogous to the superconducting order-parameter within the system naturally arises. The method can be applied to a variety of mesoscopic normal-superconducting structures, but for brevity we consider here only the case of a simple disordered N-S junction.Comment: 39 pages + 9 postscript figure

Statistics of S-matrix poles for chaotic systems with broken time reversal invariance: a conjecture

In the framework of a random matrix description of chaotic quantum scattering the positions of $S-$matrix poles are given by complex eigenvalues $Z_i$ of an effective non-Hermitian random-matrix Hamiltonian. We put forward a conjecture on statistics of $Z_i$ for systems with broken time-reversal invariance and verify that it allows to reproduce statistical characteristics of Wigner time delays known from independent calculations. We analyze the ensuing two-point statistical measures as e.g. spectral form factor and the number variance. In addition we find the density of complex eigenvalues of real asymmetric matrices generalizing the recent result by Efetov\cite{Efnh}.Comment: 4 page

Experimental study of the quantum driven pendulum and its classical analogue in atoms optics

We present experimental results for the dynamics of cold atoms in a far detuned amplitude-modulated optical standing wave. Phase-space resonances constitute distinct peaks in the atomic momentum distribution containing up to 65% of all atoms resulting from a mixed quantum chaotic phase space. We characterize the atomic behavior in classical and quantum regimes and we present the applicable quantum and classical theory, which we have developed and refined. We show experimental proof that the size and the position of the resonances in phase space can be controlled by varying several parameters, such as the modulation frequency, the scaled well depth, the modulation amplitude, and the scaled Planck's constant of the system. We have found a surprising stability against amplitude noise. We present methods to accurately control the momentum of an ensemble of atoms using these phase-space resonances which could be used for efficient phase-space state preparation