Characterization of potential new species of sulfate-reducing microorganisms isolated from Caviahue-Copahue geothermal area

GALLICET, M; SAFAR, C; CASTRO, C.; URBIETA M.S.

Bernal

Congreso; III Congreso ISME Lat 2023; 2023

Universidad Nacional de Quilmes

The Caviahue-Copahue geothermal area in Neuquén province (Argentina) has a variety of microenvi-ronments of different temperatures, from moderate to almost 90°C, that are continually changing due to the activity of the Copahue volcano. The anaerobic muds that form the geothermal ponds present a great diversi-ty of microbial species, particularly sulfate-reducing microorganisms (SRM) which play a significant role in the biogeochemical processes of the area and have potential biotechnological applications, mainly in bioremedia-tion of heavy metal contaminated environments.The aim of this study was to isolate and characterize SRM representative of different geothermal ponds of the Caviahue-Copahue system. Enrichment cultures were performed in Postgate medium in sealed vessels at pH and temperature conditions close to the environmental. Many pure cultures of SRM were achieved using streaking techniques. Their taxonomic identification by sequencing of the 16S rRNA gene rev-eled that two strains, isolate 21 and 30, were potential novel species (21: 91,34% similarity to xx and 30: 92,94% similarity to using NCBI database and BLASTn).To characterize them, both isolates were cultured in a wide range of pH and temperature (5 to 10 and 25 to 45°C, respectively) to detect optimal growth conditions. Once these parameters were determined, NaCl tolerance tests were performed (range: 10-100000 ppm). Finally, with the aim of searching biotechnological applications, metal bioprecipitation tests were performed using Nickel and Cadmium (0,05-1,0 mM) separately. The morphology of the SRM was analyzed SEM and TEM microscopies.Both strains grew in a pH range between 5.5 and 9.5 (optimum 6.5) and temperature range from 30 to 40°C (optimum 35-40°C). Both tolerated up to 0.5% NaCl. Regarding metals both strains tolerated up to 1,0 mM of Ni while one could not grow in the presence of Cd, the other tolerated up to 1,0 mM. Both isolate cells were motile rods of 2-3 µm in length and 0.5 µm in width and presented extracellular appendages. The micro-photographs revel the presence of spores.Finally, genomic DNA of both strains was extracted and sequenced. We are looking to expand our knowledge on genes and metabolic pathways to explore both strains potential biotechnological applications.