ABSTRACT
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.
Subject(s)
Archaea/classification , Archaea/genetics , Biodiversity , Metagenome , Metagenomics , Seawater/microbiology , Cations/metabolism , Cluster Analysis , DNA Transposable Elements , DNA, Archaeal/chemistry , DNA, Archaeal/genetics , DNA, Ribosomal/chemistry , DNA, Ribosomal/genetics , Genes, rRNA , Molecular Sequence Data , Phylogeny , RNA, Archaeal/genetics , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNA , Sequence Homology, Nucleic AcidABSTRACT
To detect anoxygenic bacteria containing either type 1 or type 2 photosynthetic reaction centers in a single PCR, we designed a degenerate primer set based on the bchY gene. The new primers were validated in silico using the GenBank nucleotide database as well as by PCR on pure strains and environmental DNA.
Subject(s)
Bacteria/genetics , Bacteria/isolation & purification , Bacterial Proteins/genetics , DNA Primers/genetics , Polymerase Chain Reaction/methods , Amino Acid Sequence , Anaerobiosis , Bacteria/metabolism , Molecular Sequence Data , Photosynthesis , Phylogeny , Sequence AlignmentABSTRACT
Proteorhodopsins, ubiquitous retinylidene photoactive proton pumps, were recently found in the widespread uncultured SAR86 bacterial group in oceanic surface waters. To survey proteorhodopsin diversity, new degenerate sets of proteorhodopsin primers were designed based on a genomic proteorhodopsin gene sequence originating from an Antarctic fosmid library. New proteorhodopsin variants were identified in Red Sea samples that were most similar to the original green-light absorbing proteorhodopsins found in Monterey Bay California. Unlike green-absorbing proteorhodopsins however, these new variants contained a glutamine residue at position 105, the same site recently shown to control spectral tuning in naturally occurring proteorhodopsins. Different proteorhodopsin variants were also found in the Mediterranean Sea. These proteorhodopsins formed new and distinctive proteorhodopsin groups. Phylogenetic analyses show that some of the new variants were very different from previously characterized proteorhodopsins, and formed the deepest branching groups found so far among marine proteorhodopsins. The existence of these varied proteorhodopsin sequences suggests that this class of proteins has undergone substantial evolution. These variants could represent functionally divergent paralogous genes, derived from the same or similar species, or orthologous proteorhodopsins that are distributed amongst divergent planktonic microbial taxa.
Subject(s)
Bacterial Proteins/genetics , Rhodopsin/genetics , Amino Acid Sequence , Bacterial Proteins/chemistry , Bacterial Proteins/classification , Indian Ocean , Mediterranean Region , Molecular Sequence Data , Phylogeny , Rhodopsin/chemistry , Rhodopsin/classification , Rhodopsins, Microbial , Sequence Alignment , Water MicrobiologyABSTRACT
Epidermal Leydig cells observed in the ventral epidermis of Salamandra salamandra larvae from birth until metamorphosis are characterized by large vesicles and a supporting Langerhans net. They decline in number after birth and disappear entirely after metamorphosis. The cells change in structure and become larger, thus indicating a process of degeneration. The Leydig cells are continuously removed by macrophagelike cells after birth.