Microbial Diversity of the Hypersaline Sidi Ameur and Himalatt Salt Lakes of the Algerian Sahara

Abstract

Microbial populations within hypersaline lakes often exhibit high activities of photosynthesis, dissimilatory sulphate reduction and other processes and, thus, can have profound impacts on biogeochemical cycles of carbon, nitrogen, sulphur and other important elements within arid lands. To further understand these types of ecosystems, the physicochemical and biological properties of Sidi Ameur and Himalatt Salt Lakes in the Algerian Sahara were examined and compared. Both lakes were relatively neutral in pH (7.2 to 7.4) and high in salt, at 12% and 20 % (w/v) salinity for Himalatt and Sidi Ameur Lakes, respectively, with dominant ions of sodium and chloride. The community compositions of microbes from all three domains (Bacteria, Archaea and Eukarya) were surveyed through the use of 16S and 18S ribosomal gene amplification and clone library clustering using amplified ribosomal DNA restriction analysis (ARDRA) in conjunction with DNA sequencing and analysis. A high level of microbial diversity, particularly among the bacteria of the Himalatt Salt Lake and archaea of Sidi Ameur Lake, was found within these environments. Representatives from all known halophilic bacterial phyla as well as 6 different genera of halophilic archaea were identified. Moreover, several apparently novel phylotypes among both archaea and bacteria were revealed.

Fig. 1

Sidi Ameur and Himalatt sites of the Algerian Sahara. A. The hypersaline Sidi Ameur and Himalatt sites are respectively located 55 km to the northwest and 25 km to the southeast of Bou Saâda, Algeria (latitude of 35°13′, longitude of 4°11′ and altitude of 663 m). B. Representative images of Sidi Ameur Lake depicting the barren landscape and high salt concentrations.

Fig. 2

Neighbor-joining phylogenetic tree based on archaeal 16S rDNA sequences found in the sediments and waters of Sidi Ameur site and Himalatt site [ARDARC sequences with Sidi Ameur water (WS), and sediment (SS) and Himalatt water (WH) and sediment (SH) samples indicated]. Bootstrap values (expressed as percentages of 1000 replications) > 70% are shown at branch points. S. ruber was used as an outgroup. Bar, 0.02 substitutions per nucleotide position. See methods for details and accession numbers.

Fig. 3

Phylogenetic tree based on bacterial 16S rDNA sequences found in the sediments and waters of Sidi Ameur site and Himalatt site [ARDBAC sequences with Sidi Ameur water (WS), and sediment (SS) and Himalatt water (WH) and sediment (SH) samples indicated]. Tree was constructed by neighbor-joining with bootstrap values (expressed as percentages of 1000 replications) > 70% shown at branch points. Hfx. volcanii was used as an outgroup. Bar, 0.02 substitutions per nucleotide position. See methods for details and accession numbers.