TY: THES T1 - Tolerance of amphibians and its skin symbiotic bacteria to increased salinity and acid mine drainage contamination A1 - Gabriel, Antonieta de Castro N2 - Salinity and Acid Mine Drainage (AMD) constitute environmental threats that may lead to biodiversity losses and ecosystems disturbances. The main goal of this study intended to assess the adverse effects that these two types of contamination may exert on amphibians and on its skin bacterial community. For this, the sensitivity of the skin microbiome, collected at different natural populations of Pelophylax perezi, was tested primarily to AMD, by exposing the skin bacteria isolates to serial AMD dilutions through two methodologies: Wells Diffusion and Microdilution methods. Microdilution method revealed to be more suitable to evaluate the sensitivity of the bacteria, since it allowed to better discriminating the AMD-sensitivity among bacteria. Therefore, only this method was used to proceed with the assessment of sensitivity of the skin bacterial community to NaCl. The majority of the isolates seemed to be tolerant to both pollutants (AMD and NaCl) revealing average values of the dilution/concentration causing a reduction of 20% in bacteria growth (EC20) to AMD and NaCl of 62.4% and 13.5 g/L, respectively. Tadpole?s sensitivity was assessed by exposing them, for 168 h, to different concentrations/dilutions of NaCl and AMD, respectively. In general, results showed that tadpole?s sensitivity to these pollutants was higher than its intrinsic bacterial community, in what concerns to P. perezi. Additionally, Xenopus laevis tadpoles also showed a higher sensitivity to both stressors, comparatively to the skin bacterial isolates. Between amphibian species, no differences were observed in the sensitivity to NaCl and AMD sensitivity. The capacity of amphibian skin bacteria to acquire tolerance to NaCl over a succession of exposures to low levels of this chemical was also assessed. For this, the bacteria isolate Erwinia toletana was exposed for six weeks to LB medium or to the EC10 for NaCl (18 g/L). After exposure for six weeks, the sensitivity to NaCl of the bacteria was reassessed by running again the Microdilution growth inhibition assay. Additionally, the metabolic degradation of carbon compounds were also tested to understand if there were differences on metabolic mechanisms. Results confirmed that tolerance to NaCl increased, by presenting a shift on EC20 from an initial value of 20 g/L (18.5-21.9) (for E. toletana exposed for six weeks to LB medium) to 30.8 g/L (25.4-36.3) (for E. toletana exposed for six weeks to the EC10 of NaCl). Also, the metabolic processes shown to be different between E. toletana continued exposed to LB or to NaCl, suggesting that E. toletana, when exposed to low levels of salinity (EC10), use or activated different metabolic pathways to deal with osmotic stress caused by high salinity. The study of bacterial isolates sensitivity to contaminants for bioaugmentation application in amphibians exposed to the same contaminants, present in the environment, could constitute an improvement of amphibian?s immunity defense. UR - https://ria.ua.pt/handle/10773/22390 Y1 - 2017 PB - Universidade de Aveiro