Isolation of salt-tolerant microorganisms from hypersaline water samples

FABIANA MARTÍNEZ; VERÓNICA IRAZUSTA; VERÓNICA B. RAJAL

Mar del Plata

Congreso; X Congreso Argentino de Microbiología General ? SAMIGE 2014; 2014

Mining is one of the most polluting activities, dangerous for the environment and also for the living beings. Therefore, some sustainable alternatives that allow the extraction of metals with microorganisms have been developed. These processes are known as ?biolixiviation? and they consist in having microorganisms ?attack? the minerals, so that it is finally solubilized. The main characteristic of the microorganisms that develop these capacities is their ability to survive and grow in hostile environments with high temperature, exposure to UV radiation, extreme pH, among other factors. In this work, we used water samples obtained from Salar del Hombre Muerto, in Catamarca, Argentina. These samples have high salts concentration and were analyzed to determine the presence and concentration of elements such as Li, Na, Ca, As, S, Si. The Na concentration in the water samples was about 98,000 ppm, Mg 1,000 ppm and Li about 600 ppm. These high salinity values are known to be a very limiting factor for the growth of microorganisms. Microbial growth was studied by inoculating an aliquot of the water sample in nutritive media (Yeast extract-Peptone-Dextrose and Agar Plate Count). Two experiments were carried out: first, the microorganisms were grown in media without the addition of salt. Under this condition 37 bacteria were isolated. Grown bacteria were then inoculated on salt-added media and incubated till growth. Finally, 30 different bacteria and 3 fungal strains were isolated in media containing 12,250 ppm of Na and 98.5 ppm of Li. Filamentous fungi were grown on solid Sabouraud medium with and without the addition of salt. The isolated bacteria were characterized according to their cellular wall structure and microscopic morphology through Gram staining. Out of the 30 strains, 17 were found to be Gram positive and the remaining strains (13) were Gram negative. Most of the isolated strains grew rod shaped, however cocci were found as well. Filamentous fungi were detected to show different growth morphology when growing in salt-added media in comparison with the growth in media without any addition of salt. Finally, through optical and electronic microscopy, bacteria and algae were detected in the water samples. Algae were found in different colors and morphology. Salt crystals were also observed to be in the water samples. Further investigation will be conducted to identify and select the microorganisms that have the greatest salt tolerance. Those selected microorganisms will be studied to reveal the mechanism used by microbes to survive and grow in hypersaline environments. X Congreso