ORIGINAL PAPER Prokaryotic diversity of a Tunisian multipond solar saltern Houda Baati Æ Sonda Guermazi Æ Ridha Amdouni Æ Neji Gharsallah Æ Abdelghani Sghir Æ Emna Ammar Received: 6 November 2007 / Accepted: 25 February 2008 / Published online: 29 March 2008 Ó Springer 2008 Abstract 16S rRNA gene clone libraries were separately constructed from three ponds with different salt concen- trations, M2 (15%), TS38 (25%) and S5 (32%), located within a multipond solar saltern of Sfax. The 16S rRNA genes from 216 bacterial clones and 156 archaeal clones were sequenced and phylogenetically analyzed. 44 opera- tional taxonomic units (OTUs) were generated for Bacteria and 67 for Archaea. Phylogenetic groups within the bacterial domain were restricted to Bacteroidetes and Proteobacteria, with the exception that one cyanobacterial OTU was found in the TS38 pond. 85.7, 26.6 and 25.0% of the bacterial OTUs from M2, TS38 and S5 ponds, respectively, are novel. All archaeal 16S rRNA gene sequences were exclusively affiliated with Euryarchaeota. 75.0, 60.0 and 66.7% of the OTUs from, respectively, M2, TS38 and S5 ponds are novel. The result showed that the Tunisian multipond solar saltern harbored novel prokary- otic diversity that has never been reported before for solar salterns. In addition, diversity measurement indicated a decrease of bacterial diversity and an increase of archaeal diversity with rising salinity gradient, which was in agreement with the previous observation for thalassohaline systems. Comparative analysis showed that prokaryotic diversity of Tunisian saltern was higher than that of other salterns previously studied. Keywords Solar saltern Á Molecular diversity Á Bacteria Á Archaea Á 16S rRNA genes Introduction Hypersaline ecosystems are among the most extreme environments on earth. Solar saltern ponds are an example of an environmental gradient, which has been extensively studied. These consist of a series of interconnected shallow ponds in which the concentration of salts increases as seawater evaporates, providing a wide set of ecological niches for halophilic microorganisms. Because of the limitation of traditional cultivation methods, which are not sufficient for culturing most Bacteria and Archaea (Hugenhotz et al. 1998), the use of culture-independent methods for studying prokaryotic diversity based on direct PCR amplification of the gene encoding small-subunit 16S rRNA from environmental DNA sample has proved to be a powerful means of microbial identification and evaluation Communicated by L. Huang. A. Sghir and E. Ammar have equally contributed to this work. H. Baati Á E. Ammar (&) Ecole Nationale d’Inge ´nieurs de Sfax, UR Etude et Gestion des Environnements Co ˆtiers et Urbains, BP ‘‘W’’ - 3038, Sfax, Tunisia e-mail: ammarenis@yahoo.fr S. Guermazi Á A. Sghir Universite ´ d’Evry Val d’Essonne, 2, rue Gaston Cre ´mieux, 91057 Evry, France S. Guermazi Á A. Sghir CNRS-UMR 8030- CE, Evry, France S. Guermazi Á A. Sghir CEA- Genoscope, Le Pecq, France R. Amdouni Laboratoire d’Analyse, Compagnie Ge ´ne ´rale des Salines Tunisiennes (COTUSAL), Route Gabes km 0,5, 3018 Sfax, Tunisia N. Gharsallah Laboratoire de Biotechnologie Microbienne, Faculte ´ des Sciences de Sfax, B.P. 802, 3018 Sfax, Tunisia 123 Extremophiles (2008) 12:505–518 DOI 10.1007/s00792-008-0154-x