Efecto del pastoreo sobre las gramíneas perennes Piptochaetium napostaense y Poa ligularis en relación con la distancia a la aguada

In the Caldenal region, livestock grazing occurs mainly in large areas with a single watering point thus favoring the formation of piospheres (gradients of grazing pressure). The objectives of this study were (i) to examine the density, cover, depth of the resprouting buds and the seed bank of Piptochaetium napostaense and Poa ligularis in relation to the distance to the watering point, and (ii) to investigate if the grazing pressure differentially affected these two perennial bunchgrasses. Results showed that the cover of P. napostaense is affected by the distance to the water source whereas no effects were observed in the cover of P. ligularis. The density of P. napostaense was higher in the area of intermediate grazing pressure. A detrimental effect of cattle grazing and trampling was observed in the proximity to the watering point where the seeds of P. napostaense showed the lowest germination values. Nevertheless, no seeds of P. ligularis were observed in the collected samples. Overall, it appears that the gradient of grazing pressure produces different responses in the populations of P. ligularis and P. napostaense.En el caldenal, el pastoreo en potreros de gran superficie y con una única aguada da lugar a gradientes de vegetación en relación a la fuente de agua. A fin de evaluar si el pastoreo afecta diferencia I m ente a las gramíneas forrajeras Piptochaetium napostaense y Poa ligularis, en el presente trabajo examinamos la densidad, la cobertura basal, la profundidad de yemas de renuevo y el banco de semillas de las dos especies según la distancia a la aguada. Los resultados mostraron que la cobertura de P. napostaense varia al incrementar la distancia a la aguada, mientras que se mantiene similar para P. ligularis. La densidad de plantas de P. napostaense resultó mayor en el área intermedia. La presión ejercida por el ganado produciría un mayor efecto alrededor de la fuente de agua, donde, el pastoreo y el pisoteo Impactarían sobre la densidad de semillas de P. napostaense. Por otra parte no fueron hallados propágulos de P. ligularis. Las disimilaridades entre las respuestas de las dos especies forrajeras en relación a la distancia a la aguada indicarían diferencias en la respuesta de las mismas con respecto a la presión de pastoreo

Escherichia coli Bacteriocins: Antimicrobial Efficacy and Prevalence among Isolates from Patients with Bacteraemia

Bacteriocins are antimicrobial peptides generally active against bacteria closely related to the producer. Escherichia coli produces two types of bacteriocins, colicins and microcins. The in vitro efficacy of isolated colicins E1, E6, E7, K and M, was assessed against Escherichia coli strains from patients with bacteraemia of urinary tract origin. Colicin E7 was most effective, as only 13% of the tested strains were resistant. On the other hand, 32%, 33%, 43% and 53% of the tested strains exhibited resistance to colicins E6, K, M and E1. Moreover, the inhibitory activity of individual colicins E1, E6, E7, K and M and combinations of colicins K, M, E7 and E1, E6, E7, K, M were followed in liquid broth for 24 hours. Resistance against individual colicins developed after 9 hours of treatment. On the contrary, resistance development against the combined action of 5 colicins was not observed. One hundred and five E. coli strains from patients with bacteraemia were screened by PCR for the presence of 5 colicins and 7 microcins. Sixty-six percent of the strains encoded at least one bacteriocin, 43% one or more colicins, and 54% one or more microcins. Microcins were found to co-occur with toxins, siderophores, adhesins and with the Toll/Interleukin-1 receptor domain-containing protein involved in suppression of innate immunity, and were significantly more prevalent among strains from non-immunocompromised patients. In addition, microcins were highly prevalent among non-multidrug-resistant strains compared to multidrug-resistant strains. Our results indicate that microcins contribute to virulence of E. coli instigating bacteraemia of urinary tract origin

Identification and Characterization of Microcin S, a New Antibacterial Peptide Produced by Probiotic Escherichia coli G3/10

Escherichia coli G3/10 is a component of the probiotic drug Symbioflor 2. In an in vitro assay with human intestinal epithelial cells, E. coli G3/10 is capable of suppressing adherence of enteropathogenic E. coli E2348/69. In this study, we demonstrate that a completely novel class II microcin, produced by probiotic E. coli G3/10, is responsible for this behavior. We named this antibacterial peptide microcin S (MccS). Microcin S is coded on a 50.6 kb megaplasmid of E. coli G3/10, which we have completely sequenced and annotated. The microcin S operon is about 4.7 kb in size and is comprised of four genes. Subcloning of the genes and gene fragments followed by gene expression experiments enabled us to functionally characterize all members of this operon, and to clearly identify the nucleotide sequences encoding the microcin itself (mcsS), its transport apparatus and the gene mcsI conferring self immunity against microcin S. Overexpression of cloned mcsI antagonizes MccS activity, thus protecting indicator strain E. coli E2348/69 in the in vitro adherence assay. Moreover, growth of E. coli transformed with a plasmid containing mcsS under control of an araC PBAD activator-promoter is inhibited upon mcsS induction. Our data provide further mechanistic insight into the probiotic behavior of E. coli G3/10

Shark fossil diversity (Squalomorphii, Squatinomorphii, and Galeomorphii) from the Langhian of Brielas (Lower Tagus Basin, Portugal)

The fossiliferous marine Miocene sediments of the Lower Tagus Basin (Portugal) present a great diversity of Chondrichthyes forms. The current study focuses on the fossil sharks from the Langhian Vc unit of the Brielas section, located in the Setúbal Peninsula. A total of 384 isolated fossil teeth were analysed and ascribed to 17 species from the Orders Hexanchiformes, Squaliformes, Squatiniformes, Lamniformes, and Carcharhiniformes. Centrophorus granulosus and Iago angustidens are described for the first time in Portuguese sediments, whereas Pachyscyllium dachiardii and Rhizoprionodon ficheuri represent only their second reported occurrence. Galeorhinus goncalvesi was already known from the Portuguese uppermost Miocene (Alvalade Basin), but it is now recognized in older sediments. Furthermore, the new material seems to include the first reported occurrence of Hexanchus cf. agassizi in Miocene sediments. As a whole, these new findings support the previous palaeoenvironment characterization of a warm infralittoral setting gradually deepening to a circalittoral one, where seasonal upwelling phenomena could have occurred

A Novel Protein Kinase-Like Domain in a Selenoprotein, Widespread in the Tree of Life

Selenoproteins serve important functions in many organisms, usually providing essential oxidoreductase enzymatic activity, often for defense against toxic xenobiotic substances. Most eukaryotic genomes possess a small number of these proteins, usually not more than 20. Selenoproteins belong to various structural classes, often related to oxidoreductase function, yet a few of them are completely uncharacterised

Global Analysis and Realization of a Wideband Array (250-500 MHz) for RCS Measurements in an Anechoic Chamber

International audienceA dual‐polarized array operating in the 250–500‐MHz frequency range is analyzed and realized for RCS measurements in an anechoic chamber. The elementary dual‐polarized source is presented, and then the array is completely analyzed with a parallel code solver. A comparison between computed and experimental results is given for the source impedance and radiation patterns of the array

Efecto del pastoreo en un pastizal semiárido de Argentina según la distancia a la aguada

En el bosque de caldén ( Prosopis caldenia) - región semiárida de Argentina- la ganadería ha provocado cambios en la vegetación natural. Estas áreas de pastoreo se caracterizan por ser utilizadas con potreros de gran extensión y una sola fuente de provisión de agua, por lo que se observan gradientes provocados por el pastoreo. El objetivo fue analizar las variaciones estructurales en la vegetación del caldenal en función de la distancia al abrevadero. En tres potreros se establecieron tres áreas de muestreo según las distancia a la aguada: próxima (P), intermedia (I) y lejana (L). En cada una de ellas se evaluaron la cobertura basal y densidad de las especies forrajeras y no forrajeras y la diversidad. Los resultados obtenidos en el presente trabajo muestran una disminución tanto en cobertura como en densidad de las gramíneas forrajeras en áreas próximas a la aguada. Las especies no forrajeras no presentaron variaciones a lo largo del gradiente. La menor diversidad florística se obtuvo en el sector próximo a la aguada, mientras que las de I y L fueron significativamente mayores. Nuestros resultados denotan un impacto diferencial del pastoreo en los atributos estructurales según sean las distancias a la aguada

Efecto del pastoreo en un pastizal semiárido de Argentina según la distancia a la aguada

En el bosque de caldén ( Prosopis caldenia) - región semiárida de Argentina- la ganadería ha provocado cambios en la vegetación natural. Estas áreas de pastoreo se caracterizan por ser utilizadas con potreros de gran extensión y una sola fuente de provisión de agua, por lo que se observan gradientes provocados por el pastoreo. El objetivo fue analizar las variaciones estructurales en la vegetación del caldenal en función de la distancia al abrevadero. En tres potreros se establecieron tres áreas de muestreo según las distancia a la aguada: próxima (P), intermedia (I) y lejana (L). En cada una de ellas se evaluaron la cobertura basal y densidad de las especies forrajeras y no forrajeras y la diversidad. Los resultados obtenidos en el presente trabajo muestran una disminución tanto en cobertura como en densidad de las gramíneas forrajeras en áreas próximas a la aguada. Las especies no forrajeras no presentaron variaciones a lo largo del gradiente. La menor diversidad florística se obtuvo en el sector próximo a la aguada, mientras que las de I y L fueron significativamente mayores. Nuestros resultados denotan un impacto diferencial del pastoreo en los atributos estructurales según sean las distancias a la aguada