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  • 1
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A multi-pond saltern that creates a gradient of salt concentrations has been studied with respect to some characteristics of the resulting environments and their microbial populations. The increase in salt concentration was correlated with increase in diurnal temperature and biomass present and with decrease in oxygen concentrations. Many types of organisms below 15% (w/v) total salts, were found, many of them normal inhabitants of seawater and even freshwater. Most organisms over 15% salts were halophilic. The salt concentrations comprised two ranges, each characterized by different microbial populations. First, between 15 and 30% salts, the populations ofDunaliella increased, reaching large numbers; moderately halophilic eubacteria and some fast-growing halobacteria predominated as heterotrophic microorganisms and, among the first, thePseudomonas-Alteromonas-Alcaligenes group andVibrio were the more abundant taxonomic groups; and gram-positive cocci appeared mainly over 25% salts. Phototrophic bacteria, both oxygenic and anoxygenic, were also found in this range, and among the anoxygenic type,Chromatium species andRodospirillum salexigens were probably predominant. Second, over 30% salts the diversity decreased greatly, all organisms found at the lower salt concentrations disappeared, and instead large populations of halobacteria developed. Over 50% salts, only three species of halobacteria were found.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 15 (1982), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 28 (1985), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A bacteriocin produced by Halobacterium mediterranei ATCC33500 active against many other halobacteria has been studied. Bacteriocin production is very common in eubacteria, but not in halobacteria which are representatives of a different primary kingdom: the archaebacteria. Halocin H4 production was little affected by the salt concentration or the complexity of the medium, and was not induced by UV treatment. It is a 28-kDa protein consisting of a single polypeptide chain. It is adsorbed by the target cell in which it induces lysis. The presence of bacteriocins in members of the archaebacteria is another point of similarity with eubacteria.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 23 (1984), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A purple mutant of Halobacterium halobium was isolated in a previous study. The ‘in vitro’ absorption spectra of the cells gave a broad shoulder around 570 nm. The amounts of bacteriorhodopsin were high under any growth condition (including aerobic) inhibitory for the wild-type strain. The mutant grew faster under illuminated microaerophilic conditions and showed faster proton extrusion than the wild-type strain. This evidence shows that the mutant has a constitutive bacteriorhodopsin production not influenced by the oxygen concentration in the medium. However, some stimulation by light was found.
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism 711 (1982), S. 19-25 
    ISSN: 0005-2760
    Keywords: (Halobacterium) ; Extreme halophile ; Glycolipid sulfate ; Polar lipid
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We report the presence of long stretches of tandem repeats in the genome of the halophilic Archaea Haloferax mediterranei and Haloferax volcanii A 30 bp sequence with dyad symmetry (including 5 bp inverted repeats) was repeated in tandem, interspersed with 33–39 bp unique sequences. This structure extends for long stretches — 1.4kb at one location in H. mediterranei chromosome and about 3kb in the H. volcanii chromosome. The tandem repeats (designated TREPs) show a similar distribution in both organisms, appearing once or twice in the H. volcanii and H. mediterranei chromosomes, and once in the largest, probably essential megaplasmid of each organism but not in the smaller replicons. Sequencing of the structures in both H. volcanii replicons revealed an extremely high sequence conservation in both replicons within the species, as well as in the different organisms. Homologous sequences have also been found in other more distantly related halophilic members of the Archaea. Transformation of H. volcanii with a recombinant plasmid containing a 1.1 kb fragment of the TREPs produced significant alterations in the host cells, particularly in terms of cell viability. The introduction of extra copies of TREPs within the vector significantly alters the distribution of the genome among the daughter cells, as observed by DAPI staining. Although the precise biological role cannot be completely ascertained, all the data conform with the tandem repeats being involved in replicon partitioning in halobacteria.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 17 (1995), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: A novel molecular strategy to study microbiological diversity is described. This method is based on the restriction digestion of a population of 16S rDNA sequences directly amplified from an environmental sample. Digested fragments separated by polyacrylamide electrophoresis generate characteristic profile data for estimation of diversity and overall similarities between the organisms of different environments. The methodology has been applied to a set of five ponds in a multi-pond solar saltern covering the salinity gradient from about twice that of seawater (6.4%) to NaCl precipitation (30.8%). Bacterial (eubacterial) diversity estimated from the complexity of the banding pattern obtained by restriction of the amplicons from the different ponds decreased with increasing salinity, while for Archaea (archaebacteria) the reverse was true, i.e. the higher the salinity the higher the number of bands. The similarities in taxonomic composition of the prokaryotic populations present in those ponds were evaluated from the number of restriction bands shared by the different samples. The relationships found among the different environments were independent of the enzyme used for digestion and were consistent with previous descriptions obtained by the study of isolates from the different environments. The technique appears to be promising as a rapid method for microbial biodiversity fingerprinting, useful to compare several environments and detect major shifts in species composition of the microbial population.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 9 (1993), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Two genomic sequences from the halophilic archaeon Haloferax mediterranei, where we had found PstI restriction-pattern modifications depending on the salinity of the growth medium, have been studied. A markedly salt-dependent differential expression has been detected in the nearby regions. Two of the open reading frames characterized correspond to two of the differentially expressed transcripts. In both cases the PstI sites were included in purine–pyrimidine alternancies suggestive of Z-DNA structures and located in non–coding regions with frequent repetitive motifs. A long alternating adenine-thymine tract also appears in the upstream regions of one of these open reading frames. A possible role of local DNA configuration in osmoregulation in this organism is discussed.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 124 (1994), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A rapid polymerase chain reaction (PCR) method to obtain taxa-specific DNA probes has been developed. The oligonucleotide probes derived from the sequences of species-specific (or other taxa) random amplified polymorphic DNA (RAPD) fragments. The methodology was applied to design probes for the halophilic archael species Haloferax mediterranei. With this technique, DNA probes of known sequence can be generated easily and without any previous knowledge about the properties of the microorganisms.
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  • 10
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Solar salterns, based on a multi-pond system, give a discontinuous gradient of salt concentrations. The heterotrophic bacterial populations of ponds containing from 10% salt to saturation have been studied. Saltern samples were spread on agar plates containing different media for halophilic bacteria and one medium made with water of the pond plus nutrients. Replica plating was done to determine the salt range for growth of the colonies. We studied 150 strains to determine the salt spectra of growth, the morphology, and nutrient requirements. The following conclusions were reached: (a) In salt concentrations above 10% (total salts), most bacteria are halophilic and few are halotolerant; (b) the two types of halophilic bacteria, moderate and extreme, show different distributions; in these ponds a narrow overlap exists between 25% and 32% salts with moderate halophiles predominating below this interval and extreme halophiles above it; (c) the populations of moderate halophiles are highly heterogeneous, and the salt concentration of their habitat affects their taxonomic composition, salt range for growth, and nutrient requirements. The population composition of extreme halophiles is less affected by the salt concentrations at which these bacteria are found.
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