Extreme and Heterogeneous Conditions of the Desert Wetland Chott Ech Chergui (Algeria) Allow Isolating Halophilic, Alkalophilic and Thermophilic Bacteria

Abstract

Wetlands concentrate biodiversity, particularly in arid regions. Chott Ech Chergui (Algeria), one of the biggest wetlands of the north African desert, presents extreme temperatures and salinity conditions. We initiated a physico-chemical and microbiological survey at seven sites encompassing various conditions (salt lakes, freshwater lakes and hot springs), through a one-year monthly sampling campaign. Four sites under the influence of the spring showed little temporal physio-chemical variation. Three sites displayed higher variation and the aridity level, high from late spring until autumn, was a strong predictor of water chemistry. We evidenced extremophile bacteria. Among 320 bacterial isolates tested for thermo-, acido- and alcalino- tolerance, 39, affiliated to Firmicutes and Proteobacteria, were successfully maintained and underwent physiological, biochemical and molecular characterizations. Thermotolerance was recorded up to 100 °C for a water isolate affiliated to Geobacillus stearothermophilus. Halotolerance was recorded up to 30% NaCl (w:v) for soil isolates affiliated to Salinicola zeshunii, Chromohalobacter beijerinckii and Virgibacillus halodenitrificans. Acido- and alcalo- tolerance were recorded for a pH range from 5 to 11 for several soil and water isolates affiliated to Exiguobacterium, Bacillus, Salinicola and Chromohalobacter genus. Our results comfort the interest of studying extremophile diversity in wetlands of the highly arid Sahara region.