Temperature-dependent shift from labile to recalcitrant carbon sources of arctic heterotrophs

2005 ◽  
Vol 19 (11) ◽  
pp. 1401-1408 ◽  
Author(s):  
Christina Biasi ◽  
Olga Rusalimova ◽  
Hildegard Meyer ◽  
Christina Kaiser ◽  
Wolfgang Wanek ◽  
...  
2020 ◽  
Vol 64 (4) ◽  
pp. 347-363
Author(s):  
Evelyn M. Keaveney ◽  
Alan D. Radbourne ◽  
Suzanne McGowan ◽  
David B. Ryves ◽  
Paula J. Reimer

Abstract We explored the roles of phytoplankton production, carbon source, and human activity on carbon accumulation in a eutrophic lake (Rostherne Mere, UK) to understand how changes in nutrient loading, algal community structure and catchment management can influence carbon sequestration in lake sediments. Water samples (dissolved inorganic, organic and particulate carbon) were analysed to investigate contemporary carbon sources. Multiple variables in a 55-cm sediment core, which represents the last ~ 90 years of accumulation, were studied to determine historical production rates of algal communities and carbon sources. Fluctuations in net primary production, inferred from sedimentary diatom abundance and high-performance liquid chromatography (HPLC) pigment methods, were linked to nutrient input from sewage treatment works (STW) in the catchment. Stepped combustion radiocarbon (SCR) measurements established that lake sediment contains between 11% (~ 1929 CE) and 69% (~ 1978 CE) recalcitrant carbon, with changes in carbon character coinciding with peaks in accumulation rate and linked to STW inputs. Catchment disturbance was identified by radiocarbon analysis, and included STW construction in the 1930s, determined using SCR analysis, and recent nearby highway construction, determined by measurements on dissolved organic carbon from the lake and outflow river. The quantity of autochthonous carbon buried was related to diatom biovolume accumulation rate (DBAR) and decreased when diatom accumulation rate and valve size declined, despite an overall increase in net carbon production. HPLC pigment analysis indicated that changes in total C deposition and diatom accumulation were related to proliferation of non-siliceous algae. HPLC results also indicated that dominance of recalcitrant carbon in sediment organic carbon was likely caused by increased deposition rather than preservation factors. The total algal accumulation rate controlled the sediment organic carbon accumulation rate, whereas DBAR was correlated to the proportion of each carbon source buried.


2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Donatella Tesei ◽  
Felice Quartinello ◽  
Georg M. Guebitz ◽  
Doris Ribitsch ◽  
Katharina Nöbauer ◽  
...  

Abstract Knufia chersonesos is an ascomycotal representative of black fungi, a morphological group of polyextremotolerant melanotic fungi, whose ability to resort to recalcitrant carbon sources makes it an interesting candidate for degradation purposes. A secretome screening towards polyesterases was carried out for the fungus and its non-melanized mutant, grown in presence of the synthetic copolyester Polybutylene adipate terephthalate (PBAT) as additional or sole carbon source, and resulted in the identification of 37 esterolytic and lipolytic enzymes across the established cultivation conditions. Quantitative proteomics allowed to unveil 9 proteins being constitutively expressed at all conditions and 7 which were instead detected as up-regulated by PBAT exposure. Protein functional analysis and structure prediction indicated similarity of these enzymes to microbial polyesterases of known biotechnological use such as MHETase from Ideonella sakaiensis and CalA from Candida antarctica. For both strains, PBAT hydrolysis was recorded at all cultivation conditions and primarily the corresponding monomers were released, which suggests degradation to the polymer’s smallest building block. The work presented here aims to demonstrate how investigations of the secretome can provide new insights into the eco-physiology of polymer degrading fungi and ultimately aid the identification of novel enzymes with potential application in polymer processing, recycling and degradation.


Author(s):  
T.E. Pratt ◽  
R.W. Vook

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.


1990 ◽  
Vol 64 (03) ◽  
pp. 402-406 ◽  
Author(s):  
M D Oethinger ◽  
E Seifried

SummaryThe present in vitro study investigated dose-, time- and temperature-dependent effects of two-chain urokinase plasminogen activato(u-PA, urokinase) on normal citrated plasma. When 10 μg/ml u-PA wereadded to pooled normal plasma and incubated for 30 min at an ambient temperature (25° C), α2-antiplas-min decreased to 8% of the control value. Incubation on ice yielded a decrease to 45% of control,whereas α2-antiplasmin was fully consumed at 37° C. Fibrinogen and plasminogen fell to 46% and 39%, respectively, after a 30 min incubation at 25° C. Thrombin time prolonged to 190% of control.Various inhibitors were studied with respect to their suitability and efficacy to prevent these in vitro effects. Aprotinin exhibited a good protective effect on fibrinogen at concentrations exceeding 500 KlU/ml plasma. Its use, however, was limited due to interferences with some haemostatic assays. We could demonstrate that L-Glutamyl-L-Glycyl-L-Arginyl chloromethyl ketone (GGACK) and a specific polyclonal anti-u-PA-antibody (anti-u-PA-IgG) effectively inhibited urokinase-induced plasmin generation without interfering with haemostatic assays. The anti-u-PA-antibody afforded full protection ofα2-antiplasmin at therapeutic levels of u-PA.It is concluded that u-PA in plasma samples from patients during thrombolytic therapy may induce in vitro effects which should be prevented by the use of a suitable inhibitor such as GGACK or specific anti-u-PA-antibody.


1996 ◽  
Vol 75 (03) ◽  
pp. 515-519 ◽  
Author(s):  
Mark J Post ◽  
Anke N de Graaf-Bos ◽  
George Posthuma ◽  
Philip G de Groot ◽  
Jan J Sixma ◽  
...  

Summary Purpose. Thermal angioplasty alters the thrombogenicity of the arterial wall. In previous studies, platelet adhesion was found to increase after heating human subendothelium to 55° C and decrease after heating to 90° C. In the present electron microscopic study, the mechanism of this temperature-dependent platelet adhesion to the heated arterial wall is elucidated by investigating temperature-dependent conformational changes of von Willebrand factor (vWF) and collagen types I and III and the binding of vWF to heated collagen. Methods. Purified vWF and/or collagen was applied to electron microscopic grids and heated by floating on a salt-solution of 37° C, 55° C or 90° C for 15 s. After incubation with a polyclonal antibody against vWF and incubation with protein A/gold, the grids were examined by electron microscopy. Results. At 37° C, vWF was coiled. At 55° C, vWF unfolded, whereas heating at 90° C caused a reduction in antigenicity. Collagen fibers heated to 37° C were 60.3 ± 3.1 nm wide. Heating to 55° C resulted in the unwinding of the fibers, increasing the width to 87.5 ± 8.2 nm (p < 0.01). Heating to 90° C resulted in denatured fibers with an enlarged width of 85.1 ± 6.1 nm (p < 0.05). Heating of collagen to 55° C resulted in an increased vWF binding as compared to collagen heated to 37° C or to 90° C. Incubation of collagen with vWF, prior to heating, resulted in a vWF binding after heating to 55° C that was similar to the 37° C binding and a decreased binding after 90° C. Conclusions. After 55° C heating, the von Willebrand factor molecule unfolds and collagen types I and III exhibit an increased adhesiveness for von Willebrand factor. Heating to 90° C denatures von Willebrand factor and collagen. The conformation changes of von Willebrand factor and its altered binding to collagen type I and III may explain the increased and decreased platelet adhesion to subendothelium after 55° C and 90° C heating, respectively.


1975 ◽  
Vol 34 (03) ◽  
pp. 780-794 ◽  
Author(s):  
Dianne M Kenney ◽  
Francis C Chao ◽  
James L Tullis ◽  
Gail S Conneely

SummaryThe uptake and binding of antimitotic alkaloid colchicine has been demonstrated in washed preparations of human platelets. A silicone oil technique was adapted so that both uptake and binding of 14C-colchicine were examined in the same platelet preparations. The time dependence and amount of colchicine taken up and bound by different platelet preparations during a 90 to 120 min incubation period were highly reproducible. Both colchicine uptake and binding by intact platelets, and colchicine binding by preparations of lysed platelets were specific and temperature dependent. Colchicine uptake was slowly reversible. Magnesium and GTP enhanced colchicine binding by lysed platelet preparations but calcium decreased binding.Exposure of platelets to either cold (4° C) or to thrombin, which disrupt platelet microtubules, produced significant increases in colchicine uptake and binding. The thrombin effect was maximal at 37° C and resulted in a greater increase in uptake and binding than that produced by either cold treatment alone or, by cold treatment followed by incubation with thrombin at 37° C. The amount of increase in uptake and binding produced by thrombin was independent of both thrombin (1–5 Units/109 platelets) and colchicine concentrations (1–50 × 10−6M).It is postulated that thrombin may initiate the formation, or make available, colchicine binding sites (microtubule subunits) within platelets.


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