Screening d’activités hydrolytiques extracellulaires chez des microorganismes halophiles aérobies isolés d’environnements hypersalins de l’Est algérien.

Abstract

The forms of life on earth are uncountable, as the environments which shelter them. Those developing in hostile environments are globally qualified as extrêmophiles. The first extrêmophilic organisms iso lated are a member of halophilic organisms , discovere d in an environment which we considered devoid of life, where its name: the Dead Sea. Their resistance in high salinity confers them surprising characteristics, what reveals a real biotechnological trump . A st udy having for objective, screenin g and production of hydrolases of halophilic microorganisms isolated from Algerian hypersalin e environments is realized. For that purpose, a collection of 104 halophilic aerobic prokaryotes strains isolated from the samples of water, salt and sediments tak en from four different sites (Sebkha Ezzemoul, Chott Melghir, Oued Righ and Sidi Mahdi) is constituted then phenotypical l y characterized and systematically examined to detect the qualit ative presence of four hydrolytic activities (amylase, protéase, cellul ase and lipase). A numerical analysis was also made. A dominance of short rods, Gram positive grouped in pairs or in small chains was recorded. The whole of the strains presents opt ima of pH and temperature at 7,0 - 7,5 and 37 - 40°C , respectively. The optimu m of salinity while being varied from 0 % to 25% (w/v) made it possible to reveal halotolerant, light halophilic, moderate and extreme halophil ic microorganisms . The amylolytic and protéolytic activities were the major hydrolytic activities revealed. Several strains present a combination of enzymatic activities. The numerical analysis allowed to obtain 15 phenons, clustered on the basis of the percentage of similarity between strains.