title: Spatial and seasonal prokaryotic community dynamics in ponds of increasing salinity of Sfax solar saltern in Tunisia.
abstract: The spatial and seasonal dynamics of the halophilic prokaryotic community was investigated in five ponds from Sfax solar saltern (Tunisia), covering a salinity gradient ranging from 20 to 36%. Fluorescence in situ hybridization indicated that, above 24% salinity, the prokaryotic community shifted from bacterial to archaeal dominance with a remarkable increase in the proportion of detected cells. Denaturing gradient gel electrophoresis (DGGE) profiles were rather similar in all the samples analyzed, except in the lowest salinity pond (around 20% salt) where several specific archaeal and bacterial phylotypes were detected. In spite of previous studies on these salterns, DGGE analysis unveiled the presence of microorganisms not previously described in these ponds, such as Archaea related to Natronomonas or bacteria related to Alkalimnicola, as well as many new sequences of Bacteroidetes. Some phylotypes, such as those related to Haloquadratum or to some Bacteroidetes, displayed a strong dependence of salinity and/or magnesium concentrations, which in the case of Haloquadratum could be related to the presence of ecotypes. Seasonal variability in the prokaryotic community composition was focused on two ponds with the lowest (20%) and the highest salinity (36%). In contrast to the crystallized pond, where comparable profiles between autumn 2007 and summer 2008 were obtained, the non-crystallized pond showed pronounced seasonal changes and a sharp succession of "species" during the year. Canonical correspondence analysis of biological and physicochemical parameters indicated that temperature was a strong factor structuring the prokaryotic community in the non-crystallizer pond, that had salinities ranging from 20 to 23.8% during the year.
authors.affiliation: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain.|Département des Sciences de la Vie, Faculté des Sciences de Sfax, Université de Sfax, BP 1171, Sfax, Tunisia.
authors.forename: Ines
authors.initials: I
authors.lastname: Boujelben
authors.affiliation: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain.|Departamento de Microbiología y Producción Vegetal, Universidad Miguel Hernández de Elche, Elche, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Gomariz
authors.affiliation: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain. m.martinez@ua.es.
authors.forename: Manuel
authors.initials: M
authors.lastname: Martínez-García
authors.affiliation: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Santos
authors.affiliation: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain.
authors.forename: Arantxa
authors.initials: A
authors.lastname: Peña
authors.affiliation: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: López
authors.affiliation: Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain.
authors.forename: Josefa
authors.initials: J
authors.lastname: Antón
authors.affiliation: Département des Sciences de la Vie, Faculté des Sciences de Sfax, Université de Sfax, BP 1171, Sfax, Tunisia.
authors.forename: Sami
authors.initials: S
authors.lastname: Maalej