Haloarchaeal communities in the crystallizers of two adriatic solar salterns

Abstract

Solar salterns operate only for short dry periods of the year in the north shore of the Adriatic Sea because of its relatively humid and cold Mediterranean climate. In a previous paper, we showed that the NaCl precipitation ponds (crystallizers) of Northern Adriatic Secovlje salterns have different haloarchaeal populations from those typically found in dry and hot climates such as Southern Spain. To check whether there is a common pattern of haloarchaeal diversity in these less extreme conditions, diversity in crystallizers of other Adriatic solar salterns in Ston, Croatia was ascertained by molecular and culture methods. In addition, the cultivation approach was used to further describe haloarchaeal diversity in both salterns. Over the period of two solar salt collection seasons, isolates related to species of the genera Haloferax, Haloarcula, and Haloterrigena were recovered from both salterns. Within the same sampling effort, relatives of the genus Halorubrum and a Natrinema-like isolate were cultivated from Slovenian Secovlje salterns while Halobacterium related isolates were obtained from the Croatian Ston salterns. Concurrent with our previous findings, a library of Croatian saltern crystallizer PCR-amplified 16S rRNA genes was dominated by sequences related to the genus Halorubrum. The microbial community structure was similar in both salterns but diversity indices showed greater values in Slovenian salterns when compared with Croatian salterns.

Diversity of microorganisms in solar salterns of Tamil Nadu, India

“…The specific isolates obtained were not reported from other salterns studied and thus appear to be specific for the salterns studied. Several other groups detected, e.g., Halogeometricum and Halobacterium isolates have been recovered in other solar salterns studied (Maturrano et al 2006;Pašić et al 2007) and thus appear to have a more global distribution. Likewise, the distribution of Salinibacter ruber, the dominant bacterium recovered from solar salterns, also appears to be global (Anton et al 2008).…”

“…Unlike in dry areas (Anton et al 2002), the salt is being harvested only during the dry season (March-July) while employing a continuous short-cycling salt production technique with daily salt harvests, thus dramatically shortening the time required for microbial community development. As a consequence, the microbial population densities of 10 4 cells/ml in Tamil Nadu salterns are extremely low when compared to salterns in dry area (up to 10 9 cells/ml reported from Fuencaliente, Spain; Ochsenreiter et al 2002) and even other continuous short-cycling salterns (10 6 cells/ml reported in Adriatic region; Pašić et al 2007).…”

“…The increasing salinity gradient present in the salterns is accompanied by a loss in microbial diversity with the final 'crystallizer' ponds being one of the most extreme environments on earth with respect to NaCl concentration. Although this process of salt manufacturing is well established worldwide, over the years differences in solar saltern microbial populations have repeatedly been reported (Litchfield et al 2000;Benlloch et al 2001;Anton et al 2002;Ochsenreiter et al 2002;Burns et al 2004;Pašić et al 2007;Maturrano et al 2006;Baati et al 2008). The complexity of community structures encountered strengthened the potential value that the study of diverse hypersaline environments could possess.…”

“…In comparison with other hypersaline systems, the salterns in Tamil Nadu represent novel salt production system as they are fed by inlet hypersaline bore wells brine mixed with seawater and have unique salt sedimentation surface. In its architecture (shallow ponds measuring not more than 10 cm in depth) and salt manufacturing technique, they resemble the salterns in the Adriatic region (Pašić et al 2007). Unlike in dry areas (Anton et al 2002), the salt is being harvested only during the dry season (March-July) while employing a continuous short-cycling salt production technique with daily salt harvests, thus dramatically shortening the time required for microbial community development.…”

“…On the other hand, members of some haloarchaeal genera (primarily Halobacterium and Haloferax) are readily cultivated, yet do not represent the actively growing microbial fraction and therefore remain seldom detected in clone libraries (Pedros-Alio 2006). These discrepancies have recently been diminished with advances in halophile cultivation (Burns et al 2004) leading to several reports related to the cultivable diversity in hypersaline environments (Burns et al 2004; Dave and Desai 2006;Pašić et al 2007). …”