Evaluation of bacterial diversity recovered from petroleum samples using different physical matrices

Unraveling the microbial diversity and its complexity in petroleum reservoir environments has been a challenge throughout the years. Despite the techniques developed in order to improve methodologies involving DNA extraction from crude oil, microbial enrichments using different culture conditions can be applied as a way to increase the recovery of DNA from environments with low cellular density for further microbiological analyses. This work aimed at the evaluation of different matrices (arenite, shale and polyurethane foam) as support materials for microbial growth and biofilm formation in enrichments using a biodegraded petroleum sample as inoculum in sulfate reducing condition. Subsequent microbial diversity characterization was carried out using Scanning Electronic Microscopy (SEM), Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA gene libraries in order to compare the microbial biomass yield, DNA recovery efficiency and diversity among the enrichments. The DNA from microbial communities in petroleum enrichments was purified according to a protocol established in this work and used for 16S rRNA amplification with bacterial generic primers. The PCR products were cloned, and positive clones were screened by Amplified Ribosomal DNA Restriction Analysis (ARDRA). Sequencing and phylogenetic analyses revealed that the bacterial community was mostly represented by members of the genera Petrotoga, Bacillus, Pseudomonas, Geobacillus and Rahnella. The use of different support materials in the enrichments yielded an increase in microbial biomass and biofilm formation, indicating that these materials may be employed for efficient biomass recovery from petroleum reservoir samples. Nonetheless, the most diverse microbiota were recovered from the biodegraded petroleum sample using polyurethane foam cubes as support material.(AU)

Nutrient digestibility in Arctic fox (Vulpes lagopus) fed diets containing animal meals / Digestibilidade dos nutrientes em raposa polar (Vulpes lagopus) alimentada com dietas que continham farinhas de origem animal

Three digestibility experiments on Arctic foxes were carried out. Control groups were fed standard diets (C1 and C2) composed of fresh or frozen animal by-products and steamed ground grain. Dry experimental diets (E1 and E2) contained animal meals, extracted meals and fat, were mixed with water prior to administration. In a preliminary experiment, the digestibility of dry diet E1 moistened with water for 15min and 24h was compared to determine the optimum moistening time during the experimental period proper. The preliminary experiment showed that moistening time had no significant effect on digestibility. In the main experiment, two independent digestibility trials were performed to compare the digestibility of diets fed to foxes during growth (C1 vs. E1) and fur development (C2 vs. E2). Better nutrient digestibility was noted for control diets, compared to experimental. The greatest differences were reported for total protein digestibility. Protein contained in meals undergoes denaturation during heat treatment, which reduces digestibility. It was found that the retention of nitrogen in relation to nitrogen digestion was higher in foxes fed experimental diets (E1 and E2).(AU)

Realizaram-se três ensaios de digestibilidade em raposas polares. Os grupos controles receberam dietas-padrão (C1 e C2) compostas por subprodutos de origem animal frescos ou congelados e sementes de cereais em grão. As dietas secas (E1, E2) usadas nos ensaios que continham farinha de origem animal e sementes em grãos extrudadas eram hidratadas antes de administradas. Em ensaio preliminar, avaliou-se a digestibilidade da dieta seca E1, submetida a 15 minutos e a 24 horas de hidratação. Verificou-se que o tempo de hidratação não influenciou a digestão. No experimento principal, foram realizados dois ensaios para comparar a digestibilidade das dietas fornecidas às raposas no período de crescimento (C1 vs E1) e no desenvolvimento de pelo (C2 vs E2). Melhor digestibilidade dos nutrientes foi observada para as dietas controle. As maiores diferenças foram relatadas para a proteína total. A desnaturação das proteínas, durante o tratamento térmico, reduz o índice de digestibilidade das dietas. Observou-se alto teor de retenção de hidrogênio em relação ao hidrogênio digerido nas raposas alimentadas com as dietas E1 e E2.(AU)