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1.
Proc Natl Acad Sci U S A ; 117(22): 11908-11915, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32414918

RESUMO

Water wires are critical for the functioning of many membrane proteins, as in channels that conduct water, protons, and other ions. Here, in liquid crystalline lipid bilayers under symmetric environmental conditions, the selective hydrogen bonding interactions between eight waters comprising a water wire and a subset of 26 carbonyl oxygens lining the antiparallel dimeric gramicidin A channel are characterized by 17O NMR spectroscopy at 35.2 T (or 1,500 MHz for 1H) and computational studies. While backbone 15N spectra clearly indicate structural symmetry between the two subunits, single site 17O labels of the pore-lining carbonyls report two resonances, implying a break in dimer symmetry caused by the selective interactions with the water wire. The 17O shifts document selective water hydrogen bonding with carbonyl oxygens that are stable on the millisecond timescale. Such interactions are supported by density functional theory calculations on snapshots taken from molecular dynamics simulations. Water hydrogen bonding in the pore is restricted to just three simultaneous interactions, unlike bulk water environs. The stability of the water wire orientation and its electric dipole leads to opposite charge-dipole interactions for K+ ions bound at the two ends of the pore, thereby providing a simple explanation for an ∼20-fold difference in K+ affinity between two binding sites that are ∼24 Šapart. The 17O NMR spectroscopy reported here represents a breakthrough in high field NMR technology that will have applications throughout molecular biophysics, because of the acute sensitivity of the 17O nucleus to its chemical environment.


Assuntos
Gramicidina/química , Canais Iônicos/química , Espectroscopia de Ressonância Magnética/métodos , Água/química , Sítios de Ligação , Fenômenos Biofísicos , Microambiente Celular , Biologia Computacional , Ligação de Hidrogênio , Canais Iônicos/metabolismo , Bicamadas Lipídicas/química , Bicamadas Lipídicas/metabolismo , Modelos Moleculares , Isótopos de Oxigênio/metabolismo
2.
Nat Commun ; 11(1): 2068, 2020 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-32350284

RESUMO

The resource-poor, isolated islands of Wallacea have been considered a major adaptive obstacle for hominins expanding into Australasia. Archaeological evidence has hinted that coastal adaptations in Homo sapiens enabled rapid island dispersal and settlement; however, there has been no means to directly test this proposition. Here, we apply stable carbon and oxygen isotope analysis to human and faunal tooth enamel from six Late Pleistocene to Holocene archaeological sites across Wallacea. The results demonstrate that the earliest human forager found in the region c. 42,000 years ago made significant use of coastal resources prior to subsequent niche diversification shown for later individuals. We argue that our data provides clear insights into the huge adaptive flexibility of our species, including its ability to specialize in the use of varied environments, particularly in comparison to other hominin species known from Island Southeast Asia.


Assuntos
Biodiversidade , Isótopos de Carbono/metabolismo , Geografia , Isótopos de Oxigênio/metabolismo , Animais , Ásia , Austrália , Esmalte Dentário/metabolismo , Humanos , Espectroscopia de Infravermelho com Transformada de Fourier , Dente/metabolismo
3.
Biochem Biophys Res Commun ; 524(1): 198-204, 2020 03 26.
Artigo em Inglês | MEDLINE | ID: mdl-31983430

RESUMO

Thick filaments from some striated muscles are regulated by phosphorylation of myosin regulatory light chains (RLCs). A tarantula thick filament quasi-atomic model achieved by cryo-electron microscopy has advanced our understanding on how this regulation occurs. In native thick filaments, an asymmetric intramolecular interaction between the actin-binding region of one myosin head ("blocked") and the converter region of the other head ("free") switches both heads off, establishing the myosin interacting-heads motif (IHM). This structural finding, together with motility assays, sequence analysis, and mass spectrometry (MS) observations have suggested a cooperative phosphorylation activation (CPA) mechanism for thick filament activation. In the CPA mechanism, some myosin free heads are phosphorylated constitutively in Ser35 by protein kinase C (PKC) and -under Ca2+ control - others (free or blocked) heads temporally on Ser45 by myosin light chain kinase (MLCK), in a way that explains both force development and post-tetanic potentiation in tarantula striated muscle. We tested this model using MS to verify if Ca2+-activation phosphorylates de novo un-phosphorylated Ser35 heads. For this purpose, we standardized an approach based on 18O isotopic ATP labeling to accurately detect by MS-MS the RLC phosphorylation under Ca2+-activation. MS spectra showed de novo18O incorporation only on Ser45 but not on Ser35. As the constitutive Ser35 phosphorylation cannot be dephosphorylated, this result suggests that the number of RLCs on free heads with constitutively phosphorylated Ser35 does remain constant on Ca2+-activation supporting that the myosin has a basal activation and force modulation or potentiation is controlled by MLCK Ser45 phosphorylation.


Assuntos
Marcação por Isótopo , Miosinas/metabolismo , Isótopos de Oxigênio/metabolismo , Serina/metabolismo , Aranhas/metabolismo , Sequência de Aminoácidos , Animais , Cadeias Leves de Miosina/química , Cadeias Leves de Miosina/metabolismo , Peptídeos/química , Peptídeos/metabolismo , Fosforilação
4.
Plant Physiol ; 181(3): 1175-1190, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31519787

RESUMO

Theoretical models of photosynthetic isotopic discrimination of CO2 (13C and 18O) are commonly used to estimate mesophyll conductance (g m). This requires making simplifying assumptions and assigning parameter values so that g m can be solved for as the residual term. Uncertainties in g m estimation occur due to measurement noise and assumptions not holding, including parameter uncertainty and model parametrization. Uncertainties in the 13C model have been explored previously, but there has been little testing undertaken to determine the reliability of g m estimates from the 18O model (g m18). In this study, we exploited the action of carbonic anhydrase in equilibrating CO2 with leaf water and manipulated the observed photosynthetic discrimination (Δ18O) by changing the oxygen isotopic composition of the source gas CO2 and water vapor. We developed a two-source δ18O method, whereby two measurements of Δ18O were obtained for a leaf with its gas-exchange characteristics otherwise unchanged. Measurements were performed in broad bean (Vicia faba) and Algerian oak (Quercus canariensis) in response to light and vapor pressure deficit. Despite manipulating the Δ18O by over 100‰, in most cases we observed consistency in the calculated g m18, providing confidence in the measurements and model theory. Where there were differences in g m18 estimates between source-gas measurements, we explored uncertainty associated with two model assumptions (the isotopic composition of water at the sites of CO2-water exchange, and the humidity of the leaf internal airspace) and found evidence for both. Finally, we provide experimental guidelines to minimize the sensitivity of g m18 estimates to measurement errors. The two-source δ18O method offers a flexible tool for model parameterization and provides an opportunity to refine our understanding of leaf water and CO2 fluxes.


Assuntos
Dióxido de Carbono/metabolismo , Isótopos de Oxigênio/metabolismo , Isótopos de Carbono/metabolismo , Anidrases Carbônicas/metabolismo , Fotossíntese/fisiologia , Folhas de Planta/metabolismo , Quercus/metabolismo , Água/metabolismo
5.
Methods Mol Biol ; 2046: 71-87, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31407297

RESUMO

Chip-SIP is a stable isotope probing (SIP) method for linking microbial identity and function in mixed communities and is capable of analyzing multiple isotopes (13C, 15N, and 18O) simultaneously. This method uses a high-density microarray to separate taxon-specific 16S (or 18S) rRNA genes and a high sensitivity magnetic sector secondary ion mass spectrometer (SIMS) to determine the relative isotope incorporation of the rRNA at each probe location. Using a maskless array synthesizer (MAS), we synthesize multiple unique sequences to target hundreds of taxa at the ribosomal operational taxonomic unit (OTU) level on an array surface, and then analyze it with a NanoSIMS 50, using its high-spatial resolution imaging capability to generate isotope ratios for individual probes. The Chip-SIP method has been used in diverse systems, including surface marine and estuarine water, rhizosphere, and peat soils, to quantify taxon-specific relative incorporation of different substrates in complex microbial communities. Depending on the hypothesis and experimental design, Chip-SIP allows the user to compare the same community incorporating different substrates, different communities incorporating the same substrate(s), or quantify how a community responds to treatment effects, such as temperature or nutrient concentrations.


Assuntos
DNA Bacteriano/genética , Marcação por Isótopo/métodos , Microbiota/genética , RNA Ribossômico/genética , Bactérias/genética , Isótopos de Carbono/análise , Isótopos de Carbono/metabolismo , Classificação , Espectrometria de Massas , Análise em Microsséries , Isótopos de Nitrogênio/análise , Isótopos de Nitrogênio/metabolismo , Isótopos de Oxigênio/análise , Isótopos de Oxigênio/metabolismo , Filogenia , RNA Ribossômico/metabolismo , Software
6.
Methods Mol Biol ; 2046: 129-136, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31407301

RESUMO

We describe a protocol for investigating microbial growth in environmental samples via stable isotope probing (SIP) with H218O. Water is a universal substrate for all microorganisms and replication is required for DNA to become labeled with 18O. By measuring how much the DNA of each taxon becomes enriched with 18O when an environmental sample is incubated with H218O, it is feasible to quantify that population's DNA replication rate, which is a proxy for growth.


Assuntos
Bactérias/metabolismo , DNA Bacteriano/metabolismo , Microbiologia Ambiental , Marcação por Isótopo/métodos , Isótopos de Oxigênio/metabolismo , Água/química , Bactérias/genética , DNA Bacteriano/genética
7.
Methods Mol Biol ; 2046: 137-149, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31407302

RESUMO

Quantitative stable isotope probing (qSIP) measures rates of taxon-specific element assimilation in intact microbial communities, utilizing substrates labeled with a heavy isotope.The laboratory protocol for qSIP is nearly identical to that for conventional stable isotope probing, with two key additions: (1) in qSIP, qPCR measurements are conducted on each density fraction recovered after isopycnic separation, and (2) in qSIP, multiple density fractions are sequenced spanning the entire range of densities over which nucleic acids were recovered. qSIP goes beyond identifying taxa assimilating a substrate, as it also allows for measuring that assimilation for each taxon within a given microbial community. Here, we describe an analysis process necessary to determine atom fraction excess of a heavy stable isotope added to an environmental sample for a given taxon's DNA.


Assuntos
Sondas de DNA/metabolismo , DNA Bacteriano/genética , Marcação por Isótopo/métodos , Microbiota/genética , Isótopos de Carbono/análise , Isótopos de Carbono/metabolismo , Classificação , DNA Bacteriano/metabolismo , Microbiologia Ambiental , Isótopos de Nitrogênio/análise , Isótopos de Nitrogênio/metabolismo , Isótopos de Oxigênio/análise , Isótopos de Oxigênio/metabolismo
8.
ISME J ; 13(10): 2426-2436, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31138875

RESUMO

Natural abundance of stable nitrogen (N) and oxygen (O) isotopes are invaluable biogeochemical tracers for assessing the N transformations in the environment. To fully exploit these tracers, the N and O isotope effects (15ε and 18ε) associated with the respective nitrogen transformation processes must be known. However, the N and O isotope effects of anaerobic ammonium oxidation (anammox), one of the major fixed N sinks and NO3- producers, are not well known. Here, we report the dual N and O isotope effects associated with anammox by three different anammox bacteria including "Ca. Scalindua japonica", a putative marine species, which were measured in continuous enrichment culture experiments. All three anammox species yielded similar N isotope effects of NH4+ oxidation to N2 (15εNH4→N2) ranging from 30.9‰ to 32.7‰ and inverse kinetic isotope effects of NO2- oxidation to NO3- (15εNO2→NO3 = -45.3‰ to -30.1‰). In contrast, 15εNO2→N2 (NO2- reduction to N2) were significantly different among three species, which is probably because individual anammox bacteria species might possess different types of nitrite reductase. We also report the combined O isotope effects for NO2- oxidation (18ENO2→NO3) by anammox bacteria. These obtained dual N and O isotopic effects could provide significant insights into the contribution of anammox bacteria to the fixed N loss and NO2- reoxidation (N recycling) in various natural environments.


Assuntos
Compostos de Amônio/metabolismo , Bactérias/metabolismo , Anaerobiose , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Isótopos de Nitrogênio/análise , Isótopos de Nitrogênio/metabolismo , Oxirredução , Isótopos de Oxigênio/análise , Isótopos de Oxigênio/metabolismo
9.
Plant Physiol ; 180(2): 793-812, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30952684

RESUMO

The stable carbon (δ13C) and oxygen (δ18O) isotope compositions in plant matter reflect photosynthetic and transpirative conditions in plants, respectively. However, the nature of hydrogen isotope composition (δ2H) and what it reflects of plant performance is poorly understood. Using durum wheat (Triticum turgidum var durum), this study evaluated the effect of different water and nitrogen growing field conditions on transpiration and how this effect influenced the performance of δ2H in autotrophic (flag leaf), mixotrophic (ears), and heterotrophic (grains and roots) organs. Moreover, δ2H was compared with the δ13C and δ18O in the same organs. Isotope compositions were analyzed in dry matter, the water-soluble fraction, and in water from different tissues of a set of genotypes. Similar to δ13C, the δ2H correlated negatively with stomatal conductance, whereas no correlation was observed for δ18O. Moreover, δ2H was not only affected by changes in transpiration but also by photosynthetic reactions, probably as a consequence of NADPH formation in autotrophic organs. Compared with the δ2H of stem water, plant δ2H was strongly diminished in photosynthetic organs such as the flag leaves, whereas it strongly increased in heterotrophic organs such as grains and roots. In heterotrophic organs, δ2H was associated with postphotosynthetic effects because there are several processes that lead to 2H-enrichment of carbohydrates. In summary, δ2H exhibited specific features that inform about the water conditions of the wheat crop, together with the photosynthetic characteristics of the plant part considered. Moreover, correlations of δ2H with grain yield illustrate that this isotope can be used to assess plant performance under different growing conditions.


Assuntos
Deutério/metabolismo , Hidrogênio/metabolismo , Triticum/metabolismo , Isótopos de Carbono/metabolismo , Transporte de Elétrons/efeitos dos fármacos , Modelos Lineares , Nitrogênio/farmacologia , Isótopos de Oxigênio/metabolismo , Triticum/efeitos dos fármacos , Água
10.
Proc Natl Acad Sci U S A ; 116(15): 7377-7381, 2019 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-30910962

RESUMO

Migration is an integral feature of modern mysticete whale ecology, and the demands of migration may have played a key role in shaping mysticete evolutionary history. Constraining when migration became established and assessing how it has changed through time may yield valuable insight into the evolution of mysticete whales and the oceans in which they lived. However, there are currently few data which directly assess prehistoric mysticete migrations. Here we show that calcite δ18O profiles of two species of modern whale barnacles (coronulids) accurately reflect the known migration routes of their host whales. We then analyze well-preserved fossil coronulids from three different locations along the eastern Pacific coast, finding that δ18O profiles from these fossils exhibit trends and ranges similar to modern specimens. Our results demonstrate that migration is an ancient behavior within the humpback and gray whale lineages and that multiple Pleistocene populations were undertaking migrations of an extent similar to those of the present day.


Assuntos
Migração Animal/fisiologia , Fósseis , Isótopos de Oxigênio , Baleias/fisiologia , Animais , Isótopos de Oxigênio/análise , Isótopos de Oxigênio/metabolismo , Oceano Pacífico
11.
Nat Commun ; 10(1): 742, 2019 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-30765694

RESUMO

Historical and future trends in net primary productivity (NPP) and its sensitivity to global change are largely unknown because of the lack of long-term, high-resolution data. Here we test whether annually resolved tree-ring stable carbon (δ13C) and oxygen (δ18O) isotopes can be used as proxies for reconstructing past NPP. Stable isotope chronologies from four sites within three distinct hydroclimatic environments in the eastern United States (US) were compared in time and space against satellite-derived NPP products, including the long-term Global Inventory Modeling and Mapping Studies (GIMMS3g) NPP (1982-2011), the newest high-resolution Landsat NPP (1986-2015), and the Moderate Resolution Imaging Spectroradiometer (MODIS, 2001-2015) NPP. We show that tree-ring isotopes, in particular δ18O, correlate strongly with satellite NPP estimates at both local and large geographical scales in the eastern US. These findings represent an important breakthrough for estimating interannual variability and long-term changes in terrestrial productivity at the biome scale.


Assuntos
Isótopos de Carbono/metabolismo , Ecossistema , Isótopos de Oxigênio/metabolismo , Estações do Ano , Árvores/metabolismo , Algoritmos , Conservação dos Recursos Naturais/métodos , Geografia , Modelos Biológicos , Imagens de Satélites/métodos , Árvores/crescimento & desenvolvimento , Estados Unidos
12.
PLoS One ; 14(2): e0211107, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30726270

RESUMO

As the Western Antarctic Peninsula (WAP) region responds to a warmer climate, the impacts of glacial meltwater on the Southern Ocean are expected to intensify. The Antarctic Peninsula fjord system offers an ideal system to understand meltwater's properties, providing an extreme in the meltwater's spatial gradient from the glacio-marine boundary to the WAP continental shelf. Glacial meltwater discharge in Arctic and Greenland fjords is typically characterized as relatively lower temperature, fresh and with high turbidity. During two cruises conducted in December 2015 and April 2016 in Andvord Bay, we found a water lens of low salinity and low temperature along the glacio-marine interface. Oxygen isotope ratios identified this water lens as a mixture of glacial ice and deep water in Gerlache Strait suggesting this is glacial meltwater. Conventional hydrographic measurements were combined with optical properties to effectively quantify its spatial extent. Fine suspended sediments associated with meltwater (nanoparticles of ~ 5nm) had a significant impact on the underwater light field and enabled the detection of meltwater characteristics and spatial distribution. In this study, we illustrate that glacial meltwater in Andvord Bay alters the inherent and apparent optical properties of the water column, and develop statistical models to predict the meltwater content from hydrographic and optical measurements. The predicted meltwater fraction is in good agreement with in-situ values. These models offer a potential for remote sensing and high-resolution detection of glacial meltwater in Antarctic waters. Furthermore, the possible influence of meltwater on phytoplankton abundance in the surface is highlighted; a significant correlation is found between meltwater fraction and chlorophyll concentration.


Assuntos
Clorofila/metabolismo , Fitoplâncton/fisiologia , Regiões Antárticas , Ecossistema , Estuários , Camada de Gelo , Fenômenos Ópticos , Isótopos de Oxigênio/metabolismo , Água
13.
New Phytol ; 222(3): 1271-1283, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30604465

RESUMO

The 'two-water-worlds' hypothesis is based on stable isotope differences in stream, soil and xylem waters in dual isotope space. It postulates no connectivity between bound and mobile soil waters, and preferential plant water uptake of bound soil water sources. We tested the pool-weighted impact of isotopically distinct water pools for hydrological cycling, the influence of species-specific water use and the degree of ecohydrological separation. We combined stable isotope analysis (δ18 O and δ2 H) of ecosystem water pools of precipitation, groundwater, soil and xylem water of two distinct species (Quercus suber, Cistus ladanifer) with observations of soil water contents and sap flow. Shallow soil water was evaporatively enriched during dry-down periods, but enrichment faded strongly with depth and upon precipitation events. Despite clearly distinct water sources and water-use strategies, both species displayed a highly opportunistic pattern of root water uptake. Here we offer an alternative explanation, showing that the isotopic differences between soil and plant water vs groundwater can be fully explained by spatio-temporal dynamics. Pool weighting the contribution of evaporatively enriched soil water reveals only minor annual impacts of these sources to ecosystem water cycling (c. 11% of bulk soil water and c. 14% of transpired water).


Assuntos
Modelos Biológicos , Água/metabolismo , Transporte Biológico , Cistus/metabolismo , Deutério/metabolismo , Ecossistema , Água Subterrânea/química , Isótopos de Oxigênio/metabolismo , Raízes de Plantas/metabolismo , Quercus/metabolismo , Chuva , Estações do Ano , Solo/química , Pressão de Vapor , Xilema/metabolismo
14.
J Diabetes Investig ; 10(2): 318-321, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30168293

RESUMO

The aim of the present study was to determine the total energy expenditure, physical activity and dietary intake of men with type 2 diabetes mellitus and control participants without type 2 diabetes mellitus who were matched for age and body mass index. The participants in the present study were 12 well-controlled type 2 diabetes mellitus patients and 10 controls, aged 40-75 years, with a body mass index <30 kg/m2 . Total energy expenditure under free-living conditions was assessed using the doubly labeled water method, and physical activity was measured using a triaxial accelerometer. Dietary intake was assessed using a self-recorded food intake diary during the measurement period. Participants were instructed to record their dietary intake over 3 days, including 2 weekdays. Total energy expenditure was not significantly different between the groups (P = 0.153), nor were energy (P = 0.969) or macronutrient intakes. In conclusion, when age and body mass index are matched, total energy expenditure and self-reported energy intake are not significantly different between type 2 diabetes mellitus patients and healthy controls.


Assuntos
Acelerometria/métodos , Diabetes Mellitus Tipo 2/fisiopatologia , Ingestão de Alimentos , Metabolismo Energético , Exercício Físico , Isótopos de Oxigênio/metabolismo , Água/metabolismo , Atividades Cotidianas , Índice de Massa Corporal , Estudos de Casos e Controles , Ingestão de Energia , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico
15.
Plant Biol (Stuttg) ; 21(4): 565-570, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30311347

RESUMO

Phosphorus (P) nutrition of beech ecosystems depends on soil processes, plant internal P cycling and P acquisition. P uptake of trees in the field is currently not validated due to the lack of an experimental approach applicable in natural forests. Application of radiolabelled tracers such as 33 P and 32 P is limited to special research sites and not allowed in natural environments. Moreover, only one stable isotope of P, namely 31 P, exists. One alternative tool to measure P acquisition in the field could be the use of 18 O-labelled 31 P-phosphate (31 P18 O4 3- ). Phosphate (Pi ) uptake rates calculated from the 18 O enrichment of dried root material after application of 31 Pi 18 O4 3- via nutrient solution was always lower compared to 33 P incorporation, did not show increasing rates of Pi uptake at P deficiency under controlled conditions, and did not reveal seasonal fluctuations in the field. Consequently, a clear correlation between 33 P-based and 18 O-based Pi uptake by roots could not be established. Comparison of Pi  uptake rates achieved from 33 P-Pi and 18 O-Pi application led to the conclusion of high Pi metabolism in roots after Pi uptake. The replacement of 18 O by 16 O from water in 18 O-Pi during root influx, but most probably after Pi uptake into roots, due to metabolic activities, indicates high and fast turnover of Pi . Hence, the use of 18 O-Pi as an alternative tool to estimate Pi acquisition of trees in the field must consider the increase of 18 O abundance in root water that was disregarded in dried root material.


Assuntos
Isótopos de Oxigênio/metabolismo , Fosfatos/metabolismo , Raízes de Plantas/metabolismo , Árvores/metabolismo , Transporte Biológico , Fagus/metabolismo , Radioisótopos de Fósforo/metabolismo
16.
Geobiology ; 17(2): 199-222, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30548907

RESUMO

Environmental fluctuations are recorded in a variety of sedimentary archives of lacustrine depositional systems. Geochemical signals recovered from bottom sediments in closed-basin lakes are among the most sensitive paleoenvironmental indicators and are commonly used in reconstructing lake evolution. Microbialites (i.e., organosedimentary deposits accreted through microbial trapping and binding of detrital sediment or in situ mineral precipitation on organics [Palaios, 2, 1987, 241]), however, have been largely overlooked as paleoenvironmental repositories. Here, we investigate concentrically laminated mineralized microbialites from Laguna Negra, a high-altitude (4,100 m above sea level) hypersaline, closed-basin lake in northwestern Argentina, and explore the potential for recovery of environmental signals from these unique sedimentary archives. Spatial heterogeneity in hydrological regime helps define zones inside Laguna Negra, each with their own morphologically distinct microbialite type. Most notably, platey microbialites (in Zone 3A) are precipitated by evaporative concentration processes, while discoidal oncolites (in Zone 3C) are interpreted result from fluid mixing and biologically mediated nucleation. This spatial heterogeneity is reflected in petrographically distinct carbonate fabrics: micritic, botryoidal, and isopachous. Fabric type is interpreted to reflect a combination of physical and biological influences during mineralization, and paired C-isotope measurement of carbonate and organic matter supports ecological differences as a dominant control on C-isotopic evolution between zones. Laminae of Laguna Negra microbialites preserve a range of δ13 Ccarb from +5.75‰ to +18.25‰ and δ18 Ocarb from -2.04‰ to +9.28‰. Temporal trends of lower carbon and oxygen isotopic compositions suggest that the influence of CO2 degassing associated with evaporation has decreased over time. Combined, these results indicate that microbialite archives can provide data that aid in interpretation of both lake paleohydrology and paleoenvironmental change.


Assuntos
Bactérias/metabolismo , Sedimentos Geológicos/química , Lagos/química , Argentina , Carbonatos/metabolismo , Minerais/metabolismo , Isótopos de Oxigênio/metabolismo
17.
New Phytol ; 222(1): 122-131, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30394538

RESUMO

The internal CO2 gradient imposed by mesophyll conductance (gm ) reduces substrate availability for C3 photosynthesis. With several assumptions, estimates of gm can be made from coupled leaf gas exchange with isoflux analysis of carbon ∆13 C-gm and oxygen in CO2 , coupled with transpired water (H2 O) ∆18 O-gm to partition gm into its biochemical and anatomical components. However, these assumptions require validation under changing leaf temperatures. To test these assumptions, we measured and modeled the temperature response (15-40°C) of ∆13 C-gm and ∆18 O-gm along with leaf biochemistry in the C3 grass Panicum bisulcatum, which has naturally low carbonic anhydrase activity. Our study suggests that assumptions regarding the extent of isotopic equilibrium (θ) between CO2 and H2 O at the site of exchange, and that the isotopic composition of the H2 O at the sites of evaporation ( δ w - e 18 ) and at the site of exchange ( δ w - ce 18 ) are similar, may lead to errors in estimating the ∆18 O-gm temperature response. The input parameters for ∆13 C-gm appear to be less sensitive to temperature. However, this needs to be tested in species with diverse carbonic anhydrase activity. Additional information on the temperature dependency of cytosolic and chloroplastic pH may clarify uncertainties used for ∆18 O-gm under changing leaf temperatures.


Assuntos
Dióxido de Carbono/metabolismo , Isótopos de Carbono/metabolismo , Células do Mesofilo/metabolismo , Isótopos de Oxigênio/metabolismo , Temperatura , Incerteza , Anidrases Carbônicas/metabolismo , Cloroplastos/metabolismo , Concentração de Íons de Hidrogênio , Modelos Biológicos , Ribulose-Bifosfato Carboxilase/metabolismo , Água/metabolismo
18.
mSphere ; 3(6)2018 12 19.
Artigo em Inglês | MEDLINE | ID: mdl-30567898

RESUMO

Here we report on a new nanoscale secondary ion mass spectrometry (nanoSIMS) approach based on enzyme-mediated oxygen isotope exchange, which combines the visualization of general metabolic activity in the cytoplasm with insights into the activity of enzymes related to polyphosphate (polyP) inclusions. The polyP-accumulating strain of the large sulfur bacterium Beggiatoa was used as a model organism. Beggiatoa cultures were grown under oxic and anoxic conditions when exposed to either low- or high-sulfide conditions, which are known to influence polyP metabolism in this strain. Subsequent incubation with 18O-labeled water led to high 18O enrichments above the natural background in the cytoplasm and polyP granules derived from enzymatically mediated oxygen isotope exchange. The relative importance of polyP under the different sulfide regimes became evident by an apparent continued metabolic activity at polyP inclusions under stressfully high sulfide concentrations, in contrast to a decreased general metabolic activity in the cytoplasm. This finding confirms the role of polyP as a critical component in bacterial stress response and maintenance of a survival metabolism.IMPORTANCE Microbial organisms exert a large influence on the environment as they directly affect the turnover of essential elements. This is particularly true for polyphosphate-accumulating large sulfur bacteria, which can either accumulate phosphate as polyphosphate or degrade it and release phosphate into the environment, depending on environmental conditions. This study presents a new approach to simultaneously visualize general metabolic activity and enzymatic activity at polyphosphate granules by incubation with 18O-labeled water as the only stable isotope tracer. For this purpose, the well-studied Beggiatoa sp. strain 35Flor was used as a model organism and was exposed to different stress regimes. General metabolic activity was strongly impaired during high-stress regimes. In contrast, intense intracellular polyP cycling was not restricted to favorable or stressful conditions, highlighting the importance of polyP for general cell physiology, especially during hostile conditions. The nanoSIMS approach adds a new tool to study microorganisms involved in phosphorus cycling in the environment together with the identification of general metabolic activity.


Assuntos
Beggiatoa/enzimologia , Citoplasma/enzimologia , Enzimas/análise , Corpos de Inclusão/enzimologia , Marcação por Isótopo , Isótopos de Oxigênio/metabolismo , Espectrometria de Massa de Íon Secundário/métodos , Polifosfatos/análise
19.
J Chromatogr B Analyt Technol Biomed Life Sci ; 1100-1101: 58-64, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30292950

RESUMO

We introduce a simple online 18O-labeling protocol for protein samples that uses a parallelizing microbore hollow fiber enzyme reactor (mHFER) as an alternative tool for online proteolytic digestion. Online 18O-labeling is performed by separately attaching two mHFERs in parallel to a 10-port switching valve with a high-pressure syringe pump and two syringes containing 16O- or 18O-water. 16O-/18O-labeled peptides are formed in this manner and simultaneously analyzed online using nanoflow liquid chromatography-tandem mass spectrometry (nLC-MS/MS) without any residual trypsin activity. The usefulness of a parallel mHFER platform (P-mHFER) in 18O-labeling was tested using both cytochrome C and alpha-1-acid-glycoprotein to verify the incorporation level of two 18O atoms into tryptic peptides and to provide a quantitative assessment with varied mixing ratios. Additionally, our 18O-labeling approach was used to study the serum N-glycoproteome from lung cancer patients and controls to evaluate the applicability of lectin-based quantitative N-glycoproteomics. We successfully quantified 76 peptides (from 62 N-glycoproteins). Nineteen of these peptides from lung cancer serum were up-/down-regulated at least 2.5-fold compared to controls. As a result, the P-mHFER-based online 18O-labeling platform presented here can be a simple and reproducible way to allow quantitative proteomic analysis of diverse proteome samples.


Assuntos
Reatores Biológicos , Glicoproteínas/análise , Neoplasias Pulmonares/metabolismo , Isótopos de Oxigênio/metabolismo , Proteoma/metabolismo , Cromatografia de Fase Reversa , Desenho de Equipamento , Glicoproteínas/química , Glicoproteínas/metabolismo , Humanos , Modelos Lineares , Proteoma/análise , Proteoma/química , Tripsina/metabolismo
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