Nutrient structure dynamics and microbial communities at the water-sediment interface in an extremely acidic lake in northern Patagonia.

Lake Caviahue (37° 50 'S and 71° 06' W; Patagonia, Argentina) is an extreme case of a glacial, naturally acidic, aquatic environment (pH ~ 3). Knowledge of the bacterial communities in the water column of this lake, is incipient, with a basal quantification of the bacterioplankton abundance distribution in the North and South Basins of Lake Caviahue, and the described the presence of sulfur and iron oxidizing bacteria in the lake sediments. The role that bacterioplankton plays in nutrient utilization and recycling in this environment, especially in the phosphorus cycle, has not been studied. In this work, we explore this aspect in further depth by assessing the diversity of pelagic, littoral and sediment bacteria, using state of the art molecular methods and identifying the differences and commonalties in the composition of the cognate communities. Also, we investigate the interactions between the sediments of Lake Caviahue and the microbial communities present in both sediments, pore water and the water column, to comprehend the ecological relationships driving nutrient structure and fluxes, with a special focus on carbon, nitrogen, and phosphorus. Two major environmental patterns were observed: (a) one distinguishing the surface water samples due to temperature, Fe2+, and electrical conductivity, and (b) another distinguishing winter and summer samples due to the high pH and increasing concentrations of N-NH4+, DOC and SO42-, from autumn and spring samples with high soluble reactive phosphorus (SRP) and iron concentrations. The largest bacterial abundance was found in autumn, alongside higher levels of dissolved phosphorus, iron forms, and increased conductivity. The highest values of bacterial biomass were found in the bottom strata of the lake, which is also where the greatest diversity in microbial communities was found. The experiments using continuous flow column microcosms showed that microbial growth over time, in both the test and control columns, was accompanied by a decrease in the concentration of dissolved nutrients (SRP and N-NH4+), providing proof that sediment microorganisms are active and contribute significantly to nutrient utilization/mobilization.

Characterization of Chicken IgY Specific to Clostridium difficile R20291 Spores and the Effect of Oral Administration in Mouse Models of Initiation and Recurrent Disease.

Clostridium difficile infection (CDI) are the leading cause of world-wide nosocomial acquired diarrhea. The current main clinical challenge in CDI is the elevated rate of infection recurrence that may reach up to 30% of the patients, which has been associated to the formation of dormant spores during the infection. We sought to characterize the effects of oral administration of specific anti-spore IgY in mouse models of CDI and recurrent CDI. The specificity of anti-spore IgY was evaluated in vitro. In both, initiation mouse model and recurrence mouse model, we evaluated the prophylactic and therapeutic effect of anti-spore IgY, respectively. Our results demonstrate that anti-spore IgY exhibited high specificity and titers against C. difficile spores and reduced spore adherence to intestinal cells in vitro. Administration of anti-spore IgY to C57BL/6 mice prior and during CDI delayed the appearance of the diarrhea by 1.5 day, and spore adherence to the colonic mucosa by 90%. Notably, in the recurrence model, co-administration of anti-spore IgY coupled with vancomycin delayed the appearance of recurrent diarrhea by a median of 2 days. Collectively, these observations suggest that anti-spore IgY antibodies may be used as a novel prophylactic treatment for CDI, or in combination with antibiotics to treat CDI and prevent recurrence of the infection.

Protein composition of the outermost exosporium-like layer of Clostridium difficile 630 spores.

Clostridium difficile spores are considered the morphotype of infection, transmission and persistence of C. difficile infections. There is a lack of information on the composition of the outermost exosporium layer of C. difficile spores. Using recently developed exosporium removal methods combined with MS/MS, we have established a gel-free approach to analyze the proteome of the exosporium of C. difficile spores of strain 630. A total of 184 proteins were found in the exosporium layer of C. difficile spores. We identified 7 characterized spore coat and/or exosporium proteins; 6 proteins likely to be involved in spore resistance; 6 proteins possibly involved in pathogenicity; 13 uncharacterized proteins; and 146 cytosolic proteins that might have been encased into the exosporium during assembly, similarly as reported for Bacillus anthracis and Bacillus cereus spores. We demonstrate through Flag-fusions that CotA and CotB are mainly located in the spore coat, while the exosporium collagen-like glycoproteins (i.e. BclA1, BclA2 and BclA3), the exosporium morphogenetic proteins CdeC and CdeM, and the uncharacterized exosporium proteins CdeA and CdeB are mainly located in the exosporium layer of C. difficile 630 spores. This study offers novel candidates of C. difficile exosporium proteins as suitable targets for detection, removal and spore-based therapies. BIOLOGICAL SIGNIFICANCE: This study offers a novel strategy to identify proteins of the exosporium layer of C. difficile spores and complements previous proteomic studies on the entire C. difficile spores and spore coat since it defines the proteome of the outermost layer of C. difficile spores, the exosporium. This study suggests that C. difficile spores have several proteins involved in protection against environmental stress as well as putative virulence factors that might play a role during infection. Spore exosporium structural proteins were also identified providing the ground basis for further functional studies of these proteins. Overall this work provides new protein target for the diagnosis and/or therapeutics that may contribute to combat C. difficile infections.

EVALUACIÓN DE DOS MEDIOS DE CULTIVO Y HEREDABILIDAD DE PRODUCTIVIDAD Y TIEMPO DE DESARROLLO PARA TRES MUTANTES DE Drosophila melanogaster (DROSOPHILIDAE) / Evaluation of Two Culture Media and Heritability of Productivity and Development Time for Three Mutants of Drosophila melanogaster (Drosophilidae)

Con el objetivo de investigar el efecto del medio de cultivo en la productividad y tiempo de desarrollo huevo-adulto de una cepa silvestre y tres cepas mutantes (CyLv, vg, w) de Drosophila melanogaster, se examinaron dos tipos de medios: banano y naranja. Para esto se empleó un diseño con dos factores, medio de cultivo y tipo de cepa, para un total de ocho tratamientos con cinco repeticiones cada uno. Se obtuvo que la productividad y el tiempo de desarrollo dependen del medio de cultivo y el tipo de cepa, encontrándose mayor productividad en el medio de naranja. La cepa silvestre presentó la mayor productividad y el menor tiempo de desarrollo en los dos medios (α=0,05). El análisis genético evidenció una heredabilidad baja y una variación fenotípica debida en su mayor parte al componente de interacción genotipo-ambiente, lo que explica la diferencia en el patrón de productividad y tiempo de desarrollo entre medios de cultivo.

With the objective of investigating the effect of the culture media in the productivity and development time egg-adult of Drosophila melanogaster in +/+ and three mutants (CyLv, vg, w), two culture media: banana and orange, were evaluated. An experimental design with two factors: culture media and kind of flies-stock, were tested, for a total of eight treatments with five replicas each one. The productivity and development time depend on culture media and kind of flies-stock, and the biggest productivity was in the orange culture media. The +/+ presented the biggest productivity and lowest development time in both culture media (α=0.05). The genetic analysis showed a low heritability and the phenotypic variation was due, in a mayor part, to the component of the interaction genotype-environment that explains the difference in the patron of productivity and development time between culture media.