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  • 1
    Electronic Resource
    Electronic Resource
    Osmotically induced intracellular trehalose, but not glycine betaine accumulation promotes desiccation tolerance in Escherichia coli (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 174 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Trehalose considerably increased the tolerance of Escherichia coli to air drying, whether added as an excipient prior to drying or accumulated as a compatible solute in response to osmotic stress. The protective effect of exogenously added trehalose was concentration dependent, up to a threshold value of 350 mM. However, trehalose alone cannot explain the intrinsically greater desiccation tolerance of stationary compared to exponential phase E. coli cells, although their tolerance was also enhanced by exogenous or endogenously accumulated trehalose. In contrast, glycine betaine whether added as an excipient or accumulated intracellularly had no influence on desiccation tolerance. These data demonstrate that the protection provided by compatible solutes to cells subjected to desiccation differs from that during osmotic stress, due to the much greater reduction in available cell water. The protective effects of trehalose during desiccation appear to be due to its stabilising influence on membrane structure, its chemically inert nature and the propensity of trehalose solutions to form glasses upon drying, properties which are not shared by glycine betaine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb13549.x
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  • 2
    Electronic Resource
    Electronic Resource
    Ecological significance of compatible solute accumulation by micro-organisms: from single cells to global climate (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 24 (2000), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The osmoadaptation of most micro-organisms involves the accumulation of K+ ions and one or more of a restricted range of low molecular mass organic solutes, collectively termed ‘compatible solutes’. These solutes are accumulated to high intracellular concentrations, in order to balance the osmotic pressure of the growth medium and maintain cell turgor pressure, which provides the driving force for cell extension growth. In this review, I discuss the alternative roles which compatible solutes may also play as intracellular reserves of carbon, energy and nitrogen, and as more general stress metabolites involved in protection of cells against other environmental stresses including heat, desiccation and freezing. Thus, the evolutionary selection for the accumulation of a specific compatible solute may not depend solely upon its function during osmoadaptation, but also upon the secondary benefits its accumulation provides, such as increased tolerance of other environmental stresses prevalent in the organism's niche or even anti-herbivory or dispersal functions in the case of dimethylsulfoniopropionate (DMSP). In the second part of the review, I discuss the ecological consequences of the release of compatible solutes to the environment, where they can provide sources of compatible solutes, carbon, nitrogen and energy for other members of the micro-flora. Finally, at the global scale the metabolism of specific compatible solutes (betaines and DMSP) in brackish water, marine and hypersaline environments may influence global climate, due to the production of the trace gases, methane and dimethylsulfide (DMS) and in the case of DMS, also couple the marine and terrestrial sulfur cycles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6976.2000.tb00542.x
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  • 3
    Electronic Resource
    Electronic Resource
    Osmoadaptation of Thiocapsa roseopersicina OP-1 in batch and continuous culture: Accumulation of K+ and sucrose in response to osmotic stress (1993)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 13 (1993), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Increasing growth medium NaCl concentration inhibited the growth of Thiocapsa roseopersicina OP-1 due to both an increase in the lag phase of the growth cycle and a reduction in specific growth rate. Addition of 0.05% w/v acetate to the growth medium stimulated growth at all NaCl concentrations, but this stimulation was greatest at supra-optimal NaCl concentrations. Optimal growth under all conditions tested in both batch and continuous culture was recorded at a salt concentration of 0.3 M NaCl. The intracellular concentrations of both K+ and sucrose increased linearly with increasing growth medium NaCl concentration indicating as osmoregulatory role for these solutes. Time courses of osmoadaptation in batch culture demonstrated a biphasic response to osmotic stress. The initial phase consisted of a rapid accumulation (within 30 min) of K+ from the growth medium. This was followed by a slower synthesis of sucrose which partially replaced intracellular K+ during the second phase of osmoadaptation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1993.tb00061.x
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of organic solutes accumulated by purple and green sulphur bacteria during osmotic stress using natural abundance 13C nuclear magnetic resonance spectroscopy (1993)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 13 (1993), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Natural abundance 13C NMR spectroscopy has identified sucrose and trehalose as the principle compatible solutes accumulated by non-halophilic purple and green sulphur bacteria respectively, in response to osmotic stress. Synthesis of glycine betaine as a compatible solute was rare in non-halophilic phototrophic sulphur bacteria and appears to be limited almost exclusively to halotolerant isolates, although all isolates tested were able to accumulate exogenous glycine betaine from the growth medium in response to osmotic stress. These data support the hypothesis that the degree of halotolerance of a microorganism may be due, at least in part, to the metabolic effects of the compatible solute(s) accumulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1993.tb00060.x
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  • 5
    Electronic Resource
    Electronic Resource
    Glycine betaine transport in a halotolerant Chromatium species (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 128 (1995), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The addition of 1 mM glycine betaine to the growth medium of Chromatium sp. NCIMB 8379 relieved growth inhibition caused by exposure to supra-optimal Nad concentrations. Intracellular glycine betaine concentrations were dependent upon the NaCl concentration of the growth medium up to 3 M exogenous Nad. Kinetic data for the accumulation of [methyl-14C]-glycine betaine demonstrated that Chromatium sp. NCIMB 8379 possesses a constitutively expressed active transport system for glycine betaine. The transport system was saturable with respect to glycine betaine concentration and exhibited typical Michaelis-Menten type kinetics: Km= 24 μM, Vmax= 306 nmol min−1 mg protein−1 at an external NaCl concentration of 1 M. The rate of glycine betaine transport decreased progressively with increasing growth medium NaCl concentration. This transport system may represent an adaptive response to growth in high osmolarity environments in this halotolerant isolate, allowing accumulation of glycine betaine from the external cell environment or recycling synthesised glycine betaine which has passively diffused from the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1995.tb07495.x
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  • 6
    Electronic Resource
    Electronic Resource
    Identification of trehalose and glycine betaine as compatible solutes in the moderately halophilic sulfate reducing bacterium, Desulfovibrio halophilus (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 140 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Increasing NaCl concentrations in the growth medium inhibited the growth of Desulfovibrio halophilus due to both an increase in the lag phase of growth and a reduction in the specific growth rate. Addition of 1 mM glycine betaine to the growth medium partially relieved this inhibition. Natural abundance 13C nuclear magnetic resonance spectroscopy identified the disaccharide α-α trehalose and glycine betaine as the major organic solutes accumulated by D. halophilus during growth in mineral salts medium and mineral salts medium supplemented with 1 mM glycine betaine, respectively. The presence of a weak glycine betaine transport system was confirmed by following the accumulation of [methyl-14C]glycine betaine during osmotic upshock. In the absence of exogenous glycine betaine the intracellular trehalose concentration of D. halophilus was dependent upon the osmolarity of the growth medium, with a maximum concentration of 8.3 μmol trehalose mg protein−1 recorded in cultures grown in the presence of 15% w/v NaCl. Intracellular K+ concentrations were also dependent upon the osmolarity of the growth medium over the range 3–9% w/v NaCl, but showed little further increase at higher NaCl concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08337.x
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  • 7
    Electronic Resource
    Electronic Resource
    Relationship between porewater organic carbon content, sulphate reduction and nitrogen fixation (acetylene reduction) in the rhizosphere of Zostera noltii (1996)
    Springer
    Hydrobiologia 329 (1996), S. 175-183 
    Details
    ISSN: 1573-5117
    Keywords: Acetylene reduction ; nitrogen fixation ; sulphate reduction ; acetate ; seagrasses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Depth profiles of nitrogen fixation (acetylene reduction), sulphate reduction, NH 4 + concentration and porewater volatile fatty acids concentrations were measured in Zostera noltii colonised sediments in the Bassin d'Arcachon, France in March 1994. Acetylene reduction activity (ARA) was detectable throughout sediment profiles. Addition of sodium molybdate (20 mmol l−1) a specific inhibitor of sulphate reduction to slurries inhibited ARA by 〉75% inferring that sulphate-reducing bacteria (SRB) were the dominant component of the nitrogen fixing microflora. The peak of ARA was coincident with that of sulphate reduction and a relatively constant relationship of 40 mole sulphate reduced per mole acetylene reduced was recorded throughout the profiles. From this ratio it was calculated that at least 17% of the ATP yield from sulphate reduction would be required to support the measured rates of nitrogen fixation (acetylene reduction). Acetate was the dominant constituent of the porewater volatile fatty acids pool, accounting for 〉90% of the total pool as measured by HPLC. Concentrations of porewater acetate recorded by HPLC were compared with those measured using an enzymatic technique and these data indicate that approximately 10% of the total porewater acetate pool was not available to microbial metabolism. Profiles of porewater acetate concentrations measured by both techniques were similar to those recorded for both ARA and sulphate reduction and thus acetate oxidation may fuel these activities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034556
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  • 8
    Electronic Resource
    Electronic Resource
    Seasonal variation in rates of heterotrophic nitrogen fixation (acetylene reduction) in Zostera noltii meadows and uncolonised sediments of the Bassin d'Arcachon, south-west France (1996)
    Springer
    Hydrobiologia 329 (1996), S. 161-174 
    Details
    ISSN: 1573-5117
    Keywords: Acetylene reduction ; nitrogen fixation ; sulphate reduction ; rhizosphere ; Zostera noltii ; root exudates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen fixation (acetylene reduction) rates were measured over an annual cycle in meadows of the seagrass Z. noltii and uncolonised sediments of the Bassin d'Arcachon, south-west France, using both slurry and whole core techniques. Measured rates using the slurry technique in Z. noltii colonised sediments were consistently higher than those determined in isolated cores. This was probably due to the release of labile organic carbon sources during preparation of the slurries. Thus, in colonised sediments the whole core technique may provide a more accurate estimate of in situ activity. Acetylene reduction rates measured by the whole core technique in colonised sediments were 1.8 to 4-fold greater, dependent upon the season, in the light compared with those measured in the dark, indicating that organic carbon released by the plant roots during photosynthesis was an important factor regulating nitrogen fixation. In contrast acetylene reduction rates in uncolonised sediments were independent of light. Addition of sodium molybdate, a specific inhibitor of sulphate reduction inhibited acetylene reduction activity in Z. noltii colonised sediments by 〉 80% as measured by both slurry and whole core techniques irrespective of the light regime, throughout the year inferring that sulphate reducing bacteria (SRB) were the dominant component of the nitrogen fixing microflora. A mutualistic relationship between Z. noltii and nitrogen fixing SRB in the rhizosphere, based on the exchange of organic carbon and fixed nitrogen is proposed. In uncolonised sediments sodium molybdate initially severely inhibited acetylene reduction rates, but the level of this inhibition declined over the course of the year. These data indicate that the nitrogen fixing SRB associated with the Zostera roots and rhizomes were progressively replaced by an aerobic population of nitrogen fixers associated with the decomposition of this recalcitrant high C:N ratio organic matter. Acetylene and sulphate reduction rates in the seagrass beds showed distinct summer maxima which correlated with a reduced availability of NH 4 + in the sediment and the growth cycle of Z. noltii in the Bassin. Overall, these data indicate that acetylene reduction (nitrogen fixation) activity in the rhizosphere of Z. noltii was regulated both by release of organic carbon from the plant roots and maintenance of low ammonium concentrations in the root zone due to efficient ammonium assimilation. Nitrogen fixation rates determined from acetylene reduction rates measured by the whole core technique ranged from 0.1 to 7.3 mg N m−2 d−1 in the Z. noltii beds and between 0.02 and 3.7 mg N m−2 d−1 in uncolonised sediments, dependent upon the season. Nitrogen fixation in the rhizosphere of Z. noltii was calculated to contribute between 0.4 and 1.1 g N m−2 y−1 or between 6.3 and 12% of the annual fixed nitrogen requirement of the plants. Heterotrophic nitrogen fixation therefore represents a substantial local input of fixed nitrogen to the sediments of this shallow coastal lagoon and contributes to the overall productivity of Z. noltii in this ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034555
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  • 9
    Electronic Resource
    Electronic Resource
    Short-term influence of recolonisation by the polycheate worm [2pt] Nereis succinea on oxygen and nitrogen fluxes and [2pt] denitrification: a microcosm simulation (2000)
    Springer
    Hydrobiologia 431 (2000), S. 165-174 
    Details
    ISSN: 1573-5117
    Keywords: bioturbation ; Nereis succinea ; sediment-water column fluxes ; denitrification nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The short-term effects of sediment recolonisation by Nereis succinea on sediment-water column fluxes of oxygen and dissolved inorganic nitrogen, and rates of denitrification, were studied in microcosms of homogenised, sieved sediments. The added worms enhanced oxygen uptake by the sediments, due to the increased surface area provided by the burrow walls and the degree of stimulation was stable with time. Similarly, ammonium fluxes to the water column were stimulated by N. succinea, but declined over the 3 day incubation in all microcosms including the controls. Nitrate fluxes were generally greater in the faunated microcosms, but highly variable with time. Denitrification rates were positively stimulated by N. succinea populations, denitrification of water column nitrate was stimulated 10-fold in comparison to denitrification coupled to nitrification in the sediments. Rates of denitrification of water column nitrate were not significantly different from rates in undisturbed sediment cores with similar densities of N. succinea, whereas rates of coupled nitrification–denitrification were 3-fold lower in the experimental set-up. These results may reflect the relative growth rates of nitrifying and denitrifying bacteria, which allow more rapid colonisation of new burrow surfaces by denitrifier compared to nitrifier populations. The data indicate that recolonisation by burrowing macrofauna of the highly reduced sediments of the Sacca di Goro, Lagoon, Italy, following the annual dystrophic crisis, may play a significant role in the reoxidation and detoxification of the sediments. The increased rates of denitrification associated with the worm burrows, may promote nitrogen losses, but due to the low capacity of nitrifying bacteria to colonise the new burrow structures, these losses would be highly dependent upon water column nitrate concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004088112342
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  • 10
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    Contrasting effects of bioturbation on metal toxicity of contaminated sediments results in misleading interpretation of the AVS–SEM metal-sulfide paradigm (2018)
    Royal Society of Chemistry
    In:  Environmental Science: Processes & Impacts, 20 (9). pp. 1285-1296.
    Details
    Publication Date: 2021-01-08
    Description: In undisturbed, metal-contaminated marine sediments, porewater metal concentrations are generally low due to their associations with strong binding phases such as organic matter, Fe/Mn (oxy)hydroxides and sulfides. Bioturbating fauna can alter redox conditions and, therefore, metal binding, potentially leading to increased metal bioavailability and subsequent toxicity to inhabiting organisms. Here we assessed the impacts of bioturbation (by bivalves and large amphipod species) on sediment biogeochemistry, metal bioaccumulation and toxicity to a smaller amphipod species in a metal contaminated sediment with low and high acid volatile sulfide (AVS) concentrations. Active bioturbation lowered metal toxicity to reproduction in the sediment with low-AVS (from 90% toxic (non-bioturbated) to 50% toxic (bioturbated)). This corresponded with lower dissolved metal concentrations in the overlying water column and lower metal bioaccumulation. Conversely, toxicity increased due to bioturbation in the sediment with high-AVS (40% toxic (non-bioturbated) to 80% toxic (bioturbated)), coinciding with sulfide oxidation, metal release and greater metal bioaccumulation. The results indicate that the AVS–SEM paradigm (commonly used to estimate the risks of adverse effects to benthic organisms in metal-contaminated sediments) may result in incorrect assessment outcomes in cases where bioturbating organisms rework and oxidize the sediment, or for those sediments where AVS has accumulated due to the inability of larger bioturbating benthic organisms to establish populations.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1039/c8em00266e
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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