We explored the use of Raman spectroscopy to detect organic osmotic solutes as biomarkers in the moderately halophilic heterotrophic bacterium
Halomonas elongata
grown in complex medium (accumulation ...of glycine betaine) and in defined medium with glucose as carbon source (biosynthesis of ectoine), and in the anoxygenic phototrophic
Ectothiorhodospira
marismortui
known to synthesize glycine betaine in combination with minor amounts of trehalose and
N
-α-carbamoyl glutamineamide. We tested different methods of preparation of the material: lyophilization, two-phase extraction of water-soluble molecules, and perchlorate extraction. Raman signals of glycine betaine and ectoine were detected; perchlorate extraction followed by desalting the extract on an ion retardation column gave the best results. Lyophilized cells of
E.
marismortui
showed strong signals of carotenoid pigments, and glycine betaine could be detected only after perchlorate extraction and desalting. The data presented show that Raman spectroscopy is a suitable tool to assess the mode of osmotic adaptation used by halophilic microorganisms.
Owing to the extreme salinity ( approximately 10 times saltier than the oceans), near toxic magnesium levels (approximately 2.0 M Mg(2+)), the dominance of divalent cations, acidic pH (6.0) and ...high-absorbed radiation flux rates, the Dead Sea represents a unique and harsh ecosystem. Measures of microbial presence (microscopy, pigments and lipids) indicate that during rare bloom events after exceptionally rainy seasons, the microbial communities can reach high densities. However, most of the time, when the Dead Sea level is declining and halite is precipitating from the water column, it is difficult to reliably measure the presence of microorganisms and their activities. Although a number of halophilic Archaea have been previously isolated from the Dead Sea, polar lipid analyses of biomass collected during Dead Sea blooms suggested that these isolates were not the major components of the microbial community of these blooms. In this study, in an effort to characterize the perennial microbial community of the Dead Sea and compare it with bloom assemblages, we performed metagenomic analyses of concentrated biomass from hundreds of liters of brine and of microbial material from the last massive Dead Sea bloom. The difference between the two conditions was reflected in community composition and diversity, in which the bloom was different and less diverse from the residual brine population. The distributional patterns of microbial genes suggested Dead Sea community trends in mono- and divalent cation metabolisms as well as in transposable elements. This may indicate possible mechanisms and pathways enabling these microbes to survive in such a harsh environment.
Fungal Life in the Dead Sea Oren, Aharon; Gunde-Cimerman, Nina
Biology of Marine Fungi,
2012, Letnik:
53
Book Chapter, Journal Article
Recenzirano
The waters of the Dead Sea currently contain about 348 g/l salts (2 M Mg2+, 0.5 M Ca2+, 1.5 M Na+, 0.2 M K+, 6.5 M Cl−, 0.1 M Br−). The pH is about 6.0. After rainy winters the surface waters become ...diluted, triggering development of microbial blooms. The 1980 and 1992 blooms were dominated by the unicellular green alga Dunaliella and red Archaea. At least 70 species (in 26 genera) of Oomycota (Chromista), Mucoromycotina, Ascomycota, and Basidiomycota (Fungi) were isolated from near-shore localities and offshore stations, including from deep waters. Aspergillus and Eurotium were most often recovered. Aspergillus terreus, A. sydowii, A. versicolor, Eurotium herbariorum, Penicillium westlingii, Cladosporium cladosporioides, C. sphaerospermum, C. ramnotellum, and C. halotolerans probably form the stable core of the community. The species Gymnascella marismortui may be endemic. Mycelia of Dead Sea isolates of A. versicolor and Chaetomium globosum remained viable for up to 8 weeks in Dead Sea water; mycelia of other species survived for many weeks in 50% Dead Sea water. Many isolates showed a very high tolerance to magnesium salts. There is no direct proof that fungi contribute to the heterotrophic activity in the Dead Sea, but fungi may be present at least locally and temporarily, and their enzymatic activities such as amylase, protease, and cellulase may play a role in the lake’s ecosystem.
J. Anton, A. Oren, S. Benlloch, F. Rodriguez-Valera, R. Amann and R. Rossello-Mora
Division de Microbiologia, Departamento de Fisiologia, Genetica y Microbiologia, Universidad de Alicante, Apto 99, ...03080 Alicante, Spain
Five brightly red-pigmented, motile, rod-shaped, extremely halophilic
bacteria were isolated from saltern crystallizer ponds in Alicante (two
strains) and Mallorca (three strains), Spain. They grew optimally at salt
concentrations between 20 and 30% and did not grow below 15% salts. Thus,
these isolates are among the most halophilic organisms known within the
domain Bacteria. The temperature optimum was 37--47 degrees C. A single,
yet to be identified pigment was present, with an absorption maximum at 482
nm and a shoulder at 506--510 nm. The G+C content of the DNA was 66.3--67.7
mol% and, together, they formed a homogeneous genomic group with DNA--DNA
similarities above 70%. The 16S rRNA gene sequences were almost identical
to sequences recovered earlier from the saltern biomass by amplification of
bacterial small-subunit rRNA genes from DNA extracted from the environment.
This phylotype, earlier described as 'Candidatus Salinibacter', was shown
by fluorescence in situ hybridization to contribute between 5 and 25% of
the prokaryote community of the saltern crystallizers. We have therefore
succeeded in isolating a bacterium from the natural environment that,
although being a major component of the community, was previously known by
its phylotype only. Isolation of the organism now allows formal description
of a novel genus and species, for which we propose the name Salinibacter
ruber gen. nov., sp. nov. The type strain is strain M31(T) (=DSM
13855(T)=CECT 5946(T)).
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•We use Raman spectroscopy to describe a pigment violacein from Chromobacterium violaceum.•Raman spectroscopy is a suitable tool to assess the presence of violacein.•Assignments of ...Raman bands are supported by theoretical DFT calculations.
Violacein is a bisindole pigment occurring as a biosynthetic product of Chromobacterium violaceum and Janthinobacterium lividum. It has some structural similarities to the cyanobacterial UV-protective pigment scytonemin, which has been the subject of comprehensive spectroscopic and structural studies. A detailed experimental Raman spectroscopic study with visible and near-infrared excitation of violacein produced by C. violaceum has been undertaken and supported using theoretical DFT calculations. Raman spectra with 514 and 785nm excitation of cultivated cells as well as extracts and Gaussian (B3LYP/6-311++G(d,p)) calculations with proposed molecular vibrational assignments are reported here.
We examined the presence of bacteriorhodopsin and other retinal protein pigments in the microbial community of the saltern crystallizer ponds in Eilat, Israel, and assessed the effect of the ...retinal-based proton pumps on the metabolic activity. The biota of the hypersaline (~309 g salts l
−1
) brine consisted of ~2200 β-carotene-rich
Dunaliella
cells and ~3.5 × 10
7
prokaryotes ml
−1
, most of which were flat, square or rectangular
Haloquadratum
-like archaea. No indications were obtained for massive presence of
Salinibacter
. We estimated a concentration of bacteriorhodopsin and bacteriorhodopsin-like pigments of 3.6 nmol l
−1
. When illuminated, the community respiration activity of the brine samples in which oxygenic photosynthesis was inhibited by 3-(3-4-dichlorophenyl)-1,1-dimethylurea, decreased by 40–43 %. This effect was interpreted to be the result of competition between two energy yielding systems: the bacteriorhodopsin proton pump and the respiratory chain. The results presented have important implications for the interpretation of many published data on photosynthetic and respiratory activities in hypersaline environments.
The Institute of Life Sciences and The Moshe Shilo Minerva Center for Marine Biogeochemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
Correspondence Aharon Oren ...orena{at}cc.huji.ac.il
To study biological phenomena in the Dead Sea and to simulate the effects of mixing Dead Sea water with Red Sea water, experimental mesocosms were operated at the Dead Sea Works at Sedom, Israel. Dense communities of red halophilic archaea developed in mesocosms filled with 80 % Dead Sea water and 20 % Red Sea water after enrichment with phosphate. The most common type of colonies isolated from these brines belonged to the genus Halorubrum . A few whitepinkish opaque colonies contained pleomorphic flat cells with gas vesicles. Three strains isolated from the latter colonies were characterized in depth. Their 16S rRNA gene sequences showed only 91 % similarity to the closest cultured relative ( Haloferax mediterranei ), indicating that the new strains represent a novel species of a new genus. The name Haloplanus natans gen. nov., sp. nov. is proposed for this novel organism. The type strain of Haloplanus natans is RE-101 T (=DSM 17983 T =JCM 14081 T ).
The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains RE-101 T , RE-102 and RE-103 are DQ417339 DQ417341, respectively.
A phylogenetic tree based on 16S rRNA gene sequences that includes environmental sequences showing a high degree of similarity to strains RE-101 T , RE-102 and RE-103 is available as supplementary material in IJSEM Online.
Abstract
The crustacean genus Artemia naturally inhabits various saline and hypersaline environments and is the most frequently laboratory-hatched animal for live feed in mari- and aquaculture. ...Because of its high economic importance, Artemia–bacteria interactions were so far studied mostly in laboratory strains. In this study, we focused our attention on the Artemia-associated microbiota in its natural environment in the solar salterns of Eilat, Israel. We applied a culture-independent method (clone libraries) to investigate the bacterial community structure associated with Artemia in five evaporation ponds with salinities from slightly above seawater (5%) to the point of saturation (32%), in two different developmental stages: in nauplii and in the intestine of adult animals. Bacteria found in naupliar and adult stages were classified within the Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria and Cyanobacteria. The halophilic proteobacterial genera Halomonas spp. and Salinivibrio spp. dominated the Artemia microbiota in both stages in all ponds. We also analysed a clone library of entire adult animals, revealing a novel bacterial phylogenetic lineage. This is the first molecular study of bacteria associated with two developmental stages of Artemia along a salinity gradient.
Large concentrations of mycosporine-like amino acids (MAAs) were found in a community of unicellular cyanobacteria inhabiting a gypsum crust developing on the bottom of a hypersaline saltern pond in ...Eilat, Israel. This is the first report of the occurrence of MAAs in a halophilic cyanobacterial community. Two MAAs were detected, one with an absorption maximum at 332 nm, and one at 362 nm. Intracellular MAA concentrations in the cyanobacterial community were estimated to be at least 98 mM, and this already high value is probably an underestimation. With an average molecular weight of around 300, MAAs should contribute at least 3% of the cell wet weight. While MAAs have been shown to absorb ultraviolet (UV) radiation, protecting the cells against solar radiation, they may also have an osmotic function in cyanobacterial communities inhabiting hypersaline environments, and help the cells to cope with the high salt concentrations in their environment. When the upper layer of the gypsum crust was subjected to dilution with distilled water, MAAs rapidly appeared in the outer medium, with the extent of loss of intracellular MAAs being approximately proportional to the extent of the dilution stress applied. No uptake of MAAs was observed in response to a subsequent increase in medium salinity.
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