Counts, isolation and identification of amilolytic anaerobic communities from a hot spring in Paipa (Boyacá)

The amilolytic thermophilic anaerobic microorganisms of a mineral hot spring in the Andean region (5° 45' 69’’ N, 73° 6'61’’W, 2500 m) were quantified through the Most Probable Number (MPN) technique. The microbial recounts of the populations presented values between 1.4*102cell/100 mL and 5.8*102 cell/100 mL in the presence of starch and thiosulphate as electron acceptors and 3.4*102 cel/100 mL in the presence of starch alone. Microbial isolations were conducted starting with the last positive dilutions of the MPN and 8 bacterial strains were isolated and denominated P4-6, P4-7, P4-8, P4-9, P4-10, P4-11, P4-12, and P4-13. These strains grew at optimum temperatures between 60 and 65 °C and exhibited fermentative metabolism. The main product of fermentation was ethanol followed by acetate together with hydrogen and CO2. Thiosulphate was used as external acceptor of electrons by all the isolated strains, but not sulphate or ferric iron. The phylogenetic diversity of these 8 strains was evaluated through denaturing gel gradient electrophoresis (DGGE) analysis. The sequence of the gene encoding for the 16S rRNA of two of the isolated strains (P4-6 and P4-9) was analyzed. These analyses showed that they belong to the family Thermoanaerobiaceae, domain Bacteria. From their phenotypical and genotypical characteristics, it is inferred that these organisms belong to the genus Thermoanaerobacter with similarity of 98% of the 16S rDNA with Thermoanaerobic italicus and Thermoanaerobacter mathranii. Key words: thermophile, hot springs, anaerobiosis, Thermoanaerobacter, DGGE.