Biodiversity of Archaea and floral of two inland saltern ecosystems in the Alto Vinalopó Valley, Spain.

BACKGROUND: The extraction of salt from seawater by means of coastal solar salterns is a very well-described process. Moreover, the characterization of these environments from ecological, biochemical and microbiological perspectives has become a key focus for many research groups all over the world over the last 20 years. In countries such as Spain, there are several examples of coastal solar salterns (mainly on the Mediterranean coast) and inland solar salterns, from which sodium chloride is obtained for human consumption. However, studies focused on the characterization of inland solar salterns are scarce and both the archaeal diversity and the plant communities inhabiting these environments remain poorly described. RESULTS: Two of the inland solar salterns (termed Redonda and Penalva), located in the Alto Vinalopó Valley (Alicante, Spain), were characterized regarding their geological and physico-chemical characteristics and their archaeal and botanical biodiversity. A preliminary eukaryotic diversity survey was also performed using saline water. The chemical characterization of the brine has revealed that the salted groundwater extracted to fill these inland solar salterns is thalassohaline. The plant communities living in this environment are dominated by Sarcocornia fruticosa (L.) A.J. Scott, Arthrocnemum macrostachyum (Moris) K. Koch, Suaeda vera Forsk. ex Gmelin (Amaranthaceae) and several species of Limonium (Mill) and Tamarix (L). Archaeal diversity was analyzed and compared by polymerase chain reaction (PCR)-based molecular phylogenetic techniques. Most of the sequences recovered from environmental DNA samples are affiliated with haloarchaeal genera such as Haloarcula, Halorubrum, Haloquadratum and Halobacterium, and with an unclassified member of the Halobacteriaceae. The eukaryote Dunaliella was also present in the samples. CONCLUSIONS: To our knowledge, this study constitutes the first analysis centered on inland solar salterns located in the southeastern region of Spain. The results obtained revealed that the salt deposits of this region have marine origins. Plant communities typical of salt marshes are present in this ecosystem and members of the Halobacteriaceae family can be easily detected in the microbial populations of these habitats. Possible origins of the haloarchaea detected in this study are discussed.

NMR studies of a ferredoxin from Haloferax mediterranei and its physiological role in nitrate assimilatory pathway.

Haloferax mediterranei is a halophilic archaeon that can grow in aerobic conditions with nitrate as sole nitrogen source. The electron donor in the aerobic nitrate reduction to ammonium was a ferredoxin. This ferredoxin has been purified and characterised. Air-oxidized H. mediterranei ferredoxin has a UV-visible absorption spectra typical of 2Fe-type ferredoxins with an A420/A280 of 0.21. The nuclear magnetic resonance (NMR) spectra of the ferredoxin showed similarity to those of ferredoxins from plant and bacteria, containing a [2Fe-2S] cluster. The physiological function of ferredoxin might be to serve as an electron donor for nitrate reduction to ammonium by assimilatory nitrate (EC 1.6.6.2) and nitrite reductases (EC 1.7.7.1). The apparent molecular weight (Mr) of the ferredoxin was estimated to be 21 kDa on SDS-polyacrylamide gel electrophoresis (SDS-PAGE).