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  • 1
    Electronic Resource
    Electronic Resource
    Fatty acid, compatible solute and pigment composition of obligately chemolithoautotrophic alkaliphilic sulfur-oxidizing bacteria from soda lakes (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 243 (2005), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1016/j.femsle.2004.12.004
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  • 2
    Electronic Resource
    Electronic Resource
    Chemolithotrophic haloalkaliphiles from soda lakes (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 52 (2005), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This paper summarizes recent data on the occurrence and properties of lithotrophic prokaryotes found in extremely alkaline, saline (soda) lakes. Among the chemolithotrophs found in these lakes the obligately autotrophic sulfur-oxidizing bacteria were the dominant, most diverse group, best adapted to haloalkaline conditions. The culturable forms are represented by three new genera, Thioalkalimicrobium, Thioalkalivibrio and Thioalkalispira in the Gammaproteobacteria. Among them, the genus Thioalkalivibrio was most metabolically diverse, including denitrifying, thiocyanate-oxidizing and facultatively alkaliphilic species. Culturable methane-oxidizing populations in the soda lakes belong to the type I methanotroph group in the Gammaproteobacteria, mostly in the genus Methylomicrobium. The nitrifying bacteria in hyposaline soda lakes were represented by a new species Nitrobacter alkalicus (Alphaproteobacteria), and by an alkaliphilic subspecies of Nitrosomonas halophila (Betaproteobacteria). Both belonged to the low salt-tolerant alkaliphiles. The facultatively autotrophic haloalkaliphilic isolates able to grow with hydrogen as electron donor were identified as representatives of the α-3 subclass of the Proteobacteria (aerobic) and of the Natronolimnicola–Alkalispirillum group in the gammaproteobacteria (nitrate-reducing). While all chemolithotrophic isolates from soda lakes belong to the alkaliphiles with a pH optimum for growth around 10, only the sulfur-oxidizing group included species able to grow under hypersaline conditions. This indicates that carbon and nitrogen cycles in the hypersaline alkaline lakes might not be closed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsec.2005.02.012
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  • 3
    Electronic Resource
    Electronic Resource
    Sulfur cycling in Catenococcus thiocyclus (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 19 (1996), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Since its isolation from marine volcanic areas, Catenococcus thiocyclus has been known to be able to oxidize thiosulfate to tetrathionate, but the benefits gained from the reaction were unknown. The energy to be gained from such a reaction is so small (1 electron per mol of thiosulfate, compared with 8 electrons if the thiosulfate is oxidized to sulfate) that it seemed unlikely to be a useful metabolic reaction. However, continuous culture experiments have now revealed that C. thiocyclus is able to gain metabolically useful energy from this oxidation (biomass yields increased by approximately 20% after the addition of 7.75 mM thiosulfate to medium containing 20 mM acetate) by combining it with the chemical reduction of the tetrathionate by sulfide. The enzymes for thiosulfate oxidation appear to be constitutive. Moreover, with a suitable primary energy source (e.g. glucose), C. thiocyclus can reduce sulfur (S°) to sulfide and Fe3+ to Fe2+. A chemical reaction then generates FeS. Such reactions may have important implications for the sulfur cycle at oxic:anoxic interfaces in marine and freshwater systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1996.tb00204.x
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of cytochrome c oxidase in the alkaliphilic, obligately chemolithoautotrophic, sulfur-oxidizing bacterium ‘Thioalcalomicrobium aerophilum’ strain AL 3 (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 179 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cytochrome c oxidase from the novel alkaliphilic autotrophic sulfur bacterium ‘Thioalcalomicrobium aerophilum’ strain AL 3 was isolated and purified 87-fold. Spectroscopic analysis revealed the presence of both c- and b-type hemes as well as copper in a ratio of 3:2:1. The purified enzyme consists of three subunits with apparent molecular masses of 41, 34 and 32 kDa. The two small subunits contain covalently bound heme c. With TMPD as a substrate the pH optimum was determined to be pH 8.0. In the presence of monovalent cations the specific activity of the purified oxidase increased significantly. The enzyme was not able to oxidize external cytochrome c, but accepted electron from its native electron donor. The latter was separated from the other membrane cytochromes during anion-exchange chromatography and was identified as a high potential cytochrome c551. Overall the data indicate that the cytochrome c oxidase from this alkaliphilic autotrophic bacterium belongs to the heme-copper oxidase superfamily; regarding its subunit composition and content of prosthetic groups, the enzyme is similar in many aspects to the cbb3-type cytochrome c oxidases described for several neutrophilic bacteria, including anaerobic phototrophic and aerobic sulfur-oxidizing bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb08713.x
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  • 5
    Electronic Resource
    Electronic Resource
    Haloalkaliphilic sulfur-oxidizing bacteria in soda lakes (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 29 (2005), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The existence of chemolithoautotrophic sulfur-oxidizing bacteria (SOB) capable of growth in an extremely alkaline and saline environment has not been recognized until recently. Extensive studies of saline, alkaline (soda) lakes located in Central Asia, Africa and North America have now revealed the presence, at relatively high numbers, of a new branch of obligately autotrophic SOB in these doubly extreme environments. Overall more than 100 strains were isolated in pure culture. All of them have the potential to grow optimally at around pH 10 in media strongly buffered with sodium carbonate/bicarbonate and cannot grow at pH 〈 7.5 and Na+ concentration 〈0.2 M. The majority of the isolates fell into two distinct groups with differing phylogeny and physiology, that have been described as two new genera in the Gammaproteobacteria; Thioalkalimicrobium and Thioalkalivibrio. The third genus, Thioalkalispira, contains a single obligate microaerophilic species T. microaerophila. The Thioalkalimicrobium group represents a typical opportunistic strategy, including highly specialized, relatively fast-growing and low salt-tolerant bacteria, dominating in hyposaline steppe soda lakes of Central Asia. The genus Thioalkalivibrio includes mostly slowly growing species better adapted to life in hypersaline conditions and with a more versatile metabolism. It includes denitrifying, thiocyanate-utilizing and facultatively alkaliphilic species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsre.2004.10.005
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  • 6
    Electronic Resource
    Electronic Resource
    Anaerobic oxidation of thiosulfate to tetrathionate by obligately heterotrophic bacteria, belonging to the Pseudomonas stutzeri group (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 30 (1999), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A number of strains of heterotrophic bacteria were isolated from various environments on the basis of their potential to oxidize inorganic sulfur compounds to tetrathionate. The isolates were screened for the ability to oxidize thiosulfate under denitrifying conditions. Many of them could grow anaerobically with acetate and nitrate, and eight strains could oxidize thiosulfate to tetrathionate under the same conditions. In batch cultures with acetate as carbon and energy source, most active anaerobic thiosulfate oxidation occurred with N2O as electron acceptor. The level of anaerobic thiosulfate-oxidizing activity in cultures and cell suspensions supplied with nitrate correlated with the activity of nitrite reductase in cell suspensions. Some strains converted thiosulfate to tetrathionate equally well with nitrite, nitrate and N2O as electron acceptors. Others functioned best with N2O during anaerobic thiosulfate oxidation. The latter strains appeared to have a lower level of nitrite reductase activity. Thiosulfate oxidation under anaerobic conditions was much slower than in the presence of oxygen, and was obviously controlled by the availability of organic electron donor. The strains had DNA-DNA similarity levels higher than 30%. Sequence analysis of the 16S rRNA gene of four selected isolates showed their affiliation to specific genomovars of Pseudomonas stutzeri and the proposed new species, Pseudomonas balearica. As shown by 16S rRNA sequence analysis and DNA-DNA hybridization, the previously misnamed ‘Flavobacterium lutescens’ (ATCC 27951) is also a P. stutzeri strain which can oxidize thiosulfate to tetrathionate aerobically and anaerobically in the presence of N2O. The data suggest that tetrathionate-forming heterotrophic bacteria, in particular those belonging to the P. stutzeri‘superspecies’, can play a much more significant role in the biogeochemical cycles than was previously recognized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1999.tb00640.x
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  • 7
    Electronic Resource
    Electronic Resource
    An obligate methylotrophic, methane-oxidizing Methylomicrobium species from a highly alkaline environment (2000)
    Springer
    Extremophiles 4 (2000), S. 145-155 
    Details
    ISSN: 1433-4909
    Keywords: Key words Alkaliphiles ; Methane-oxidizing bacteria ; Methanotroph ; Ammonia oxidation ; Soda lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new, obligately methylotrophic, methane-oxidizing bacterium, strain AMO 1, was isolated from a mixed sample of sediments from five highly alkaline soda lakes (Kenya). Based on its cell ultrastructure and high activity of the hexulose-6-phosphate synthase, the new isolate belongs to the type I methanotrophs. It differed, however, from the known neutrophilic methanotrophs by the ability to grow and oxidize methane at high pH values. The bacterium grew optimally with methane at pH 9–10. The oxidation of methane, methanol, and formaldehyde was optimal at pH 10, and cells were still active up to pH 11. AMO 1 was able to oxidize ammonia to nitrite at high pH. A maximal production of nitrite from ammonia in batch cultures at pH 10 was observed with 10% of CH4 in the gas phase when nitrate was present as nitrogen source. Washed cells of AMO 1 oxidized ammonia most actively at pH 10–10.5 in the presence of limiting amounts of methanol or CH4. The bacterium was also capable of oxidizing organic sulfur compounds at high pH. Washed cells grown with methane exhibited high activity of CS2 oxidation and low, but detectable, levels of DMS and DMDS oxidation. The GC content of AMO 1 was 50.9 mol%. It showed only weak DNA homology with the previously described alkaliphilic methanotroph "Methylobacter alcaliphilus" strain 20 Z and with the neutrophilic species of the genera Methylobacter and Methylomonas. According to the 16S rRNA gene sequence analysis, strain AMO 1 was most closely related to a neutrophilic methanotroph, Methylomicrobium pelagicum (98.2% sequence similarity), within the gamma-Proteobacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007920070029
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