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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 122 (1994), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Using high performance liquid chromatography and nuclear magnetic resonance techniques, the compatible solutes of some moderately halophilic bacteria were studied. The following accepted species of moderately halophilic bacteria were included: Volcaniella eurihalina and Deleya salina among Gram-negative rods, and Salinicoccus roseus and Salinicoccus hispanicus among Gram-positive cocci. Besides these strains we have also screened other new isolates, including Marinomonas species and Gram-positive cocci and rods. The tetrahydropyrimidine carboxylic acid ‘ectoine’ was found to be the main compatible solute in the Gram-negative strains tested when these were grown in glucose-mineral medium. In addition, betaine was accumulated from complex media containing yeast extract. Among the Gram-positive strains investigated, the solutes proline (bacillus 30, Salinicoccus) and hydroxyectoine (coccus 28) also played an important role, while alanine, glucose, glutamate, glutamine and trehalose occurred as minor components. We also detected two recently described compatible solutes: Nδ-acetylornithine and a homologous compound, Nε-acetyllysine. Representatives of distinct phenotypic groups of Gram-positive cocci and rods were clearly distinguished by their solute pattern.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 165 (1998), 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 161 (1998), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Using transposon mutagenesis we generated a salt-sensitive mutant of the halophilic eubacterium Halomonas elongata impaired in the biosynthesis of the compatible solute ectoine. HPLC determinations of the cytoplasmic solute content showed the accumulation of a biosynthetic precursor of ectoine, l-2,4-diaminobutyric acid. Ectoine and hydroxyectoine were not detectable. This mutant failed to grow in minimal medium with NaCl concentrations exceeding 4%. However, when supplemented with organic osmolytes, the ability to grow in high-salinity medium (15% and higher) was regained. We cloned and sequenced the regions flanking the transposon insertion in the H. elongata chromosome. Sequence comparisons with known proteins revealed significant similarity of the mutated gene to the l-2,4-diaminobutyric acid acetyltransferase from the ectoine biosynthetic pathway in Marinococcus halophilus. Analysis of a PCR product demonstrated that the ectoine biosynthetic genes (ectABC) follow the same order as in M. halophilus.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 15 (1994), S. 0 
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Salt stress is primarily osmotic stress, and halophilic/halotolerant microorganisms have evolved two basic mechanisms of osmoadaplation: the KCI-type and the compatible-solute type, the latter representing a very flexible mode of adaptation making use of distinct stabilizing properties of compatible solutes. A comprehensive survey, using HPLC and NMR methods, has revealed the full diversity of euhacterial compatible solutes found in nature. With the exception of proline (a proteinogenic amino acid) they are characterized as amino acid derivatives of the following types: betaines, ectoines, N-acetylated diamino acids and N-derivatized carboxamides of glutamine. From our present knowledge of hiosynthetic pathways it appears that, apart from glycine betaine, all nitrogen-containing compatible solutes originate from two major pathways (the aspartate branch and the glutamate branch). Uptake of compatible solutes from the growth medium (environment) seems to have preference over de novo synthesis. Therefore in the natural ecosystem the solutes of primary producers (mainly glycine betaine), which are readily excreted upon dilution stress, certainly play an important role as a ‘preferred’ solute source for heterolrophic organisms, and as a ‘vital’ source for organisms unable to synthesize their own compatible solutes.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 109 (1993), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The aim of our investigation was to study the haloadaptation of a number of species of Gram-positive bacteria belonging to the genera Brevibacterium and Corynebacterium. We used two different HPLC-techniques and 13C-NMR spectroscopy for the identification of osmolytes (compatible solutes). The tetrahydropyrimidines (‘ectoines’) are the main compatible solutes in the genus Brevibacterium, whereas accumulation of glycine-betaine and accumulation of synthesis of glutamine is mainly responsible for osmoadaptation in the genus Corynebacterium. Pipecolic acid, formerly described as a potential osmolyte synthesized de novo in C. ammoniagenes, does not contribute markedly to the solute pool, unless supplemented to the medium.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Salt adaptation in chemolithotrophic alkaliphilic sulfur-oxidizing strains belonging to genera Thioalkalimicrobium and Thioalkalivibrio has been studied by determination of salt-dependent changes in fatty acid and compatible solute composition. In both alkaliphilic groups, represented by the low salt-tolerant Thioalkalimicrobium aerophilum strain AL 3T and the extremely salt-tolerant Thioalkalivibrio versutus strain ALJ 15, unsaturated fatty acids predominate over saturated fatty acids. In strain AL 3T, C18:1, C16:0 and C16:1 were the dominant fatty acids. In strain ALJ 15, the concentrations of C18:1 and C19cyclo were salt-regulated in an inverse proportional relationship, suggesting the stimulation of cyclopropyl-synthetase activity. Squalene has been found in substantial amounts only in strain ALJ 15. Ectoine and glycine betaine were found to be the main osmolytes in Thioalkalimicrobium aerophilum and Thioalkalivibrio versutus, respectively. The production of ectoine and glycine betaine was positively correlated with the salt concentration in the growth medium. A novel type of membrane-bound yellow pigments was uniformly detected in the extremely salt-tolerant strains of Thioalkalivibrio with a backbone consisting of C15-polyene, whose specific concentration correlated with increasing salinity of the growth medium. The results suggest that the mechanisms of haloalkaliphilic adaptation in Thioalkalimicrobium sp. and Thioalkalivibrio sp. involve the production of cyclopropane fatty acids, organic compatible solutes and, possibly specific pigments.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 75 (1990), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Most halophilic and halotolerant eubacteria are able to accumulate compatible solutes from their environment during salt stress. They are usually able to synthesize sugars and amino acids. These compatible solutes, however, are of less importance in extremely halophilic eubacteria, where usually glycinebetaine or ectoine is required. Extremely halophilic phototrophic sulfur bacteria of the genus Ectothiorhodospira are able to synthesize the three compatible solutes glycinebetaine, trehalose and ectoine. While glycinebetaine is the major compatible solute under all conditions the percentage of trehalose and ectoine varies depending on the availability of nitrogen sources. Using acetate plus bicarbonate as simultaneous substrates the three compatible solutes were analysed by 13C-NMR spectroscopy. The label found indicated the following biosynthesis pathways: glycine, derived from glyoxylate out of the Kornberg cycle, undergoes a three-fold methylation with S-adenosylmethionine as methyl donor. The latter is derived from the tetrahydrofolate pathway. Several enzymes of this pathway have been found and are under investigation. The labelling of trehalose indicates that the Calvin cycle is blocked in the presence of acetate. The two glucose moieties of trehalose are linked by trehalose-6-phosphate synthase. The enzyme was characterized. Ectoine is synthesized from aspartate via aspartophosphate, aspartate semialdehyde and α, β-diaminobutyrate. Dilution stress leads to rapid excretion of betaine and ectoine, followed by immediate uptake to balance overshoot excretion. Trehalose is not excreted under dilution stress but is degraded by trehalase and subsequently metabolized.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Marine luminescent bacteria of the genera Vibrio and Photobacterium as well as Photorhabdus (Xenorhabdus) luminescens, an enterobacterium mutualistically associated with insect pathogenic soil nematodes, display different levels of salt tolerance when grown on nutrient broth medium (5% w/v NaCl for marine species and 3% w/v for Prb. luminescens). Osmolytes (compatible solutes) synthesized and/or accumulated for haloadaptation were identified using HPLC techniques and 13C-NMR spectroscopy. All species investigated in this study accumulated betaine and ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidine carboxylic acid) from the medium under elevated osmotic conditions. External supply of osmolytes improved both growth and salt tolerance. Only species belonging to the genus Vibrio were able to synthesize the compatible solute ectoine de novo. Glutamate also participated in osmoadaptation while trehalose was only found in V. fischeri species. In Prb. luminescens13C-NMR spectroscopy also revealed the presence of choline when grown on complex medium.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 128 (1995), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Molecular genetic studies of halophilic eubacteria have been limited by the lack of a suitable method for mutagenesis. To overcome this, we established a transposon mutagenesis procedure for the ectoine-producing, halophilic bacterium Halomonas elongata. We used suicide plasmids pSUP101 and pSUP102-Gm to introduce the transposons Tn5 and Tn7732 respectively into H. elongata via Escherichia coli SM10 mediated conjugation. Our finding that H. elongata is sensitive to aminoglycoside antibiotics at low salinity enabled us to apply transposons that mediate kanamycin resistance. The insertions of transposon In 1732 occurred at different sites in the chromosome of H. elongata, as proved by Southern hybridization analysis. Phenotypic analysis revealed that different auxotrophic and salt sensitive mutants were generated by mutagenesis with transposon Tn1732. To our knowledge this is the first report of a successful application of a transposon for direct generalized mutagenesis in a halophilic eubacterium.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 37 (1992), S. 61-65 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The aim of this study was to elucidate the protective effect of the new compatible solutes, ectoine and hydroxyectoine, on two sensitive enzymes (lactic dehydrogenase, phosphofructokinase). The solutes tested also included (for reasons of comparison) other compatible solutes such as glycine betaine and a number of disaccharides (sucrose, trehalose, maltose). All compatible solutes under investigation displayed remarkable stabilizing capabilities. However, the degree of protection depended on both the type of solute chosen and the enzyme used as a test system. The most prominent protectants were trehalose, ectoine and hydroxyectoine, which are very often found in nature (singly or in combinationn) as part of the compatible solute “cocktail” of moderately halophilic eubacteria.
    Type of Medium: Electronic Resource
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