Prokaryotic diversity in Aran-Bidgol salt lake, a thalasohaline lake in Iran, was studied by fluorescence in situ hybridization (FISH), cultivation techniques, denaturing gradient gel electrophoresis (DGGE) of PCR-amplified fragments of 16S rRNA genes and 16S rRNA gene clone library analysis. Viable counts obtained (2.5-4 × 10(6) cells mL(-1)) were similar to total cell abundance in the lake determined by DAPI direct count (3-4×10(7) cells mL(-1)). The proportion of Bacteria to Archaea in the community detectable by FISH was unexpectedly high and ranged between 1:3 and 1:2. We analyzed 101 archaeal isolates and found that most belonged to the genera Halorubrum (55%) and Haloarcula (18%). Eleven bacterial isolates obtained in pure culture were affiliated with the genera Salinibacter (18.7%), Salicola (18.7%) and Rhodovibrio (35.3%). Analysis of inserts of 100 clones from the eight 16S rRNA clone libraries constructed revealed 37 OTUs. The majority (63%) of these sequences were not related to any previously identified taxa. Within this sampling effort we most frequently retrieved phylotypes related to Halorhabdus (16% of archaeal sequences obtained) and Salinibacter (36% of bacterial sequences obtained). Other prokaryotic groups that were abundant included representatives of Haloquadratum, the anaerobic genera Halanaerobium and Halocella, purple sulfur bacteria of the genus Halorhodospira and Cyanobacteria.

Two Gram-staining-negative, red- and orange-pigmented, non-motile, rod-shaped, extremely halophilic bacteria, designated strains CB7^T and DGO^T, were isolated from Aran-Bidgol salt lake, Iran. Growth occurred at NaCl concentrations of between 2 and 5 M NaCl and the isolates grew optimally with 3 M NaCl. The optimum pH and temperature for growth of the two strains were pH 7.5 and 37 °C, and they were able to grow over pH and temperature ranges of pH 6–8 and 25–50 °C. The predominant fatty acids of the two isolates were C_18 : 1ω7c, iso-C_15 : 0 and summed feature 3 (C_16 : 1ω7c and/or iso-C_15 : 0 2-OH). The polar lipid pattern of the two isolates consisted of diphosphatidylglycerol, phosphatidylcholine, three unidentified lipids, one unidentified aminolipid and three unidentified glycolipids. The only quinone present was menaquinone 7 (MK-7). The G+C contents of the genomic DNA of strains CB7^T and DGO^T were 64.8 and 65.6 mol%, respectively. 16S rRNA gene sequence analysis indicated that strains CB7^T and DGO^T were related to Salinibacter ruber in the phylum Bacteroidetes . Levels of 16S rRNA gene sequence similarity between strains CB7^T and DGO^T and Salinibacter ruber DSM 13855^T were 93.2 and 93.6 %, respectively. The two novel strains shared 98.9 % 16S rRNA gene sequence similarity. DNA–DNA hybridization experiments between strains CB7^T and DGO^T and Salinibacter ruber DSM 13855^T indicated levels of relatedness of 44 and 52 %, respectively, while the level of relatedness between the two new isolates was 53 %. Chemotaxonomic data supported the placement of strains CB7^T and DGO^T in the genus Salinibacter . DNA–DNA hybridization studies and biochemical and physiological characterization allowed strains CB7^T and DGO^T to be differentiated from Salinibacter ruber and from each other. They are therefore considered to represent two novel species of the genus Salinibacter , for which the names Salinibacter iranicus sp. nov. (type strain CB7^T = IBRC-M 10036^T = CGMCC 1.11003^T) and Salinibacter luteus sp. nov. (type strain DGO^T = IBRC-M 10423^T = CGMCC 1.11002^T) are proposed. Emended descriptions of the genus Salinibacter and of Salinibacter ruber are also presented.

Halophiles are the organisms that thrive in extreme high salt environments. Despite the extensive studies on their biotechnological potentials, the ability of halophilic prokaryotes for the synthesis of nanoparticles has remained understudied. In this study, the archaeal and bacterial halophiles from a solar saltern were investigated for the intracellular/extracellular synthesis of silver and selenium nanoparticles. Silver nanoparticles were produced by the archaeal Haloferax sp. (AgNP-A, intracellular) and the bacterial Halomonas sp. (AgNP-B, extracellular), while the intracellular selenium nanoparticles were produced by the archaeal Halogeometricum sp. (SeNP-A) and the bacterial Bacillus sp. (SeNP-B). The nanoparticles were characterized by various techniques including UV-Vis spectroscopy, XRD, DLS, ICP-OES, Zeta potentials, FTIR, EDX, SEM, and TEM. The average particle size of AgNP-A and AgNP-B was 26.34 nm and 22 nm based on TEM analysis. Also, the characteristic Bragg peaks of face-centered cubic with crystallite domain sizes of 13.01 nm and 6.13 nm were observed in XRD analysis, respectively. Crystallographic characterization of SeNP-A and SeNP-B strains showed a hexagonal crystallite structure with domain sizes of 30.63 nm and 29.48 nm and average sizes of 111.6 nm and 141.6 nm according to TEM analysis, respectively. The polydispersity index of AgNP-A, AgNP-B, SeNP-A, and SeNP-B was determined as 0.26, 0.28, 0.27, and 0.36 and revealed high uniformity of the nanoparticles. All of the synthesized nanoparticles were stable and their zeta potentials were calculated as (mV): ˗33.12, ˗35.9, ˗31.2, and ˗29.34 for AgNP-A, AgNP-B, SeNP-A, and SeNP-B, respectively. The nanoparticles showed the antibacterial activity against various bacterial pathogens. The results of this study suggested that the (extremely) halophilic prokaryotes have great potentials for the green synthesis of nanoparticles.