(Thèse partie 1)

Summary
Hypersaline lakes constitute a typical example of extreme environments which
shelter halophilic microbial communities adapted to this condition. In this work, we used
cultural approaches in conjunction with molecular methods to investigate microbial
communities of brines of Ezzemoul sabkha located in Ain M’Lila (Oum El Bouaghi).
About forty strains of Archaea and Bacteria were isolated, purified and characterized.
The archaeal strains belonging to Halobacteriaceae family, order of Halobaceriales. All
are extremely halophilic, aerobic, Gram-negative and mesophilic. In addition, they are
neutrophilic. Their cells are pleomorphic. The characterization of polar lipid and
phylogenetic study of the strains have affiliated them to the genera: Halobacterium,
Haloarcula, Halobaculum, Halococcus, Haloferax, Halorubrum and Haloterrigena. On
the basis of the phenotypic and genotypic data, a novel species named Halorubrum
ezzemoulense sp. nov. was described.
The two bacterial isolates are rod-shaped, Gram-negative, neutrophilic, mesophilic and
aerobic. They are identified as extremely and moderate halophilic bacteria, respectively
and belong to Gamma-Proteobacteria. Based on the results of our taxonomic study, a
novel extremely halophilic species of bacteria named Salicola salis sp. nov. is particularly
described. Moreover, this research work revealed that halophilic archaea strains dominate.
Key words: extremely halophilic, Archaea, Bacteria, haloarchaea, sequencing,
hybridization DNA-DNA, sabkha, hypersaline environments, microbial diversity,
phylogeny.