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1.
Phys Rev Lett ; 132(12): 126502, 2024 Mar 22.
Artículo en Inglés | MEDLINE | ID: mdl-38579201

RESUMEN

LiCu_{3}O_{3} is an antiferromagnetic mixed valence cuprate where trilayers of edge-sharing Cu(II)O (3d^{9}) are sandwiched in between planes of Cu(I) (3d^{10}) ions, with Li stochastically substituting Cu(II). Angle-resolved photoemission spectroscopy (ARPES) and density functional theory reveal two insulating electronic subsystems that are segregated in spite of sharing common oxygen atoms: a Cu d_{z^{2}}/O p_{z} derived valence band (VB) dispersing on the Cu(I) plane, and a Cu 3d_{x^{2}-y^{2}}/O 2p_{x,y} derived Zhang-Rice singlet (ZRS) band dispersing on the Cu(II)O planes. First-principle analysis shows the Li substitution to stabilize the insulating ground state, but only if antiferromagnetic correlations are present. Li further induces substitutional disorder and a 2D electron glass behavior in charge transport, reflected in a large 530 meV Coulomb gap and a linear suppression of VB spectral weight at E_{F} that is observed by ARPES. Surprisingly, the disorder leaves the Cu(II)-derived ZRS largely unaffected. This indicates a local segregation of Li and Cu atoms onto the two separate corner-sharing Cu(II)O_{2} sub-lattices of the edge-sharing Cu(II)O planes, and highlights the ubiquitous resilience of the entangled two hole ZRS entity against impurity scattering.

2.
Ann Hematol ; 103(6): 1931-1940, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38478023

RESUMEN

Ruxolitinib is beneficial in patients with myelofibrosis (MF) and polycythemia vera (PV). Information on ruxolitinib adherence is scant. The Ruxolitinib Adherence in Myelofibrosis and Polycythemia Vera (RAMP) prospective multicenter study (NCT06078319) included 189 ruxolitinib-treated patients. Patients completed the Adherence to Refills and Medications Scale (ARMS) and Distress Thermometer and Problem List (DTPL) at the earliest convenience, after registration in the study, and at later timepoints. At week-0, low adherence (ARMS > 14) and high distress (DT ≥ 4) were declared by 49.7% and 40.2% of patients, respectively. The main reason for low adherence was difficult ruxolitinib supply (49%), intentional (4.3%) and unintentional (46.7%) non-take. In multivariable regression analysis, low adherence was associated to male sex (p = 0.001), high distress (p < 0.001), and treatment duration ≥ 1 year (p = 0.03). Over time, rates of low adherence and high distress remained stable, but unintentional non-take decreased from 47.9% to 26.0% at week-48. MF patients with stable high adherence/low distress were more likely to obtain/maintain the spleen response at week-24. Low adherence to ruxolitinib represents an unmet clinical need that require a multifaceted approach, based on reason behind it (patients characteristics and treatment duration). Its recognition may help distinguishing patients who are truly refractory and those in need of therapy optimization.


Asunto(s)
Cumplimiento de la Medicación , Nitrilos , Policitemia Vera , Mielofibrosis Primaria , Pirazoles , Pirimidinas , Humanos , Mielofibrosis Primaria/tratamiento farmacológico , Pirimidinas/uso terapéutico , Pirazoles/uso terapéutico , Masculino , Policitemia Vera/tratamiento farmacológico , Femenino , Estudios Prospectivos , Anciano , Persona de Mediana Edad , Italia/epidemiología , Cumplimiento de la Medicación/estadística & datos numéricos , Anciano de 80 o más Años , Adulto
3.
Environ Sci Technol ; 58(19): 8349-8359, 2024 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-38696360

RESUMEN

Agricultural ponds are a significant source of greenhouse gases, contributing to the ongoing challenge of anthropogenic climate change. Nations are encouraged to account for these emissions in their national greenhouse gas inventory reports. We present a remote sensing approach using open-access satellite imagery to estimate total methane emissions from agricultural ponds that account for (1) monthly fluctuations in the surface area of individual ponds, (2) rates of historical accumulation of agricultural ponds, and (3) the temperature dependence of methane emissions. As a case study, we used this method to inform the 2024 National Greenhouse Gas Inventory reports submitted by the Australian government, in compliance with the Paris Agreement. Total annual methane emissions increased by 58% from 1990 (26 kilotons CH4 year-1) to 2022 (41 kilotons CH4 year-1). This increase is linked to the water surface of agricultural ponds growing by 51% between 1990 (115 kilo hectares; 1,150 km2) and 2022 (173 kilo hectares; 1,730 km2). In Australia, 16,000 new agricultural ponds are built annually, expanding methane-emitting water surfaces by 1,230 ha yearly (12.3 km2 year-1). On average, the methane flux of agricultural ponds in Australia is 0.238 t CH4 ha-1 year-1. These results offer policymakers insights into developing targeted mitigation strategies to curb these specific forms of anthropogenic emissions. For instance, financial incentives, such as carbon or biodiversity credits, can mobilize widespread investments toward reducing greenhouse gas emissions and enhancing the ecological and environmental values of agricultural ponds. Our data and modeling tools are available on a free cloud-based platform for other countries to adopt this approach.


Asunto(s)
Agricultura , Gases de Efecto Invernadero , Metano , Estanques , Metano/análisis , Gases de Efecto Invernadero/análisis , Australia , Monitoreo del Ambiente , Cambio Climático
4.
Glob Chang Biol ; 28(15): 4701-4712, 2022 08.
Artículo en Inglés | MEDLINE | ID: mdl-35562855

RESUMEN

Agricultural practices have created tens of millions of small artificial water bodies ("farm dams" or "agricultural ponds") to provide water for domestic livestock worldwide. Among freshwater ecosystems, farm dams have some of the highest greenhouse gas (GHG) emissions per m2 due to fertilizer and manure run-off boosting methane production-an extremely potent GHG. However, management strategies to mitigate the substantial emissions from millions of farm dams remain unexplored. We tested the hypothesis that installing fences to exclude livestock could reduce nutrients, improve water quality, and lower aquatic GHG emissions. We established a large-scale experiment spanning 400 km across south-eastern Australia where we compared unfenced (N = 33) and fenced farm dams (N = 31) within 17 livestock farms. Fenced farm dams recorded 32% less dissolved nitrogen, 39% less dissolved phosphorus, 22% more dissolved oxygen, and produced 56% less diffusive methane emissions than unfenced dams. We found no effect of farm dam management on diffusive carbon dioxide emissions and on the organic carbon in the soil. Dissolved oxygen was the most important variable explaining changes in carbon fluxes across dams, whereby doubling dissolved oxygen from 5 to 10 mg L-1 led to a 74% decrease in methane fluxes, a 124% decrease in carbon dioxide fluxes, and a 96% decrease in CO2 -eq (CH4 + CO2 ) fluxes. Dams with very high dissolved oxygen (>10 mg L-1 ) showed a switch from positive to negative CO2 -eq. (CO2 + CH4 ) fluxes (i.e., negative radiative balance), indicating a positive contribution to reduce atmospheric warming. Our results demonstrate that simple management actions can dramatically improve water quality and decrease methane emissions while contributing to more productive and sustainable farming.


Asunto(s)
Gases de Efecto Invernadero , Metano , Animales , Dióxido de Carbono/análisis , Ecosistema , Granjas , Gases de Efecto Invernadero/análisis , Ganado , Metano/análisis , Óxido Nitroso/análisis , Oxígeno , Calidad del Agua
5.
New Phytol ; 229(5): 2647-2659, 2021 03.
Artículo en Inglés | MEDLINE | ID: mdl-33156533

RESUMEN

Cell size influences the rate at which phytoplankton assimilate dissolved inorganic carbon (DIC), but it is unclear whether volume-specific carbon uptake should be greater in smaller or larger cells. On the one hand, Fick's Law predicts smaller cells to have a superior diffusive CO2 supply. On the other, larger cells may have greater scope to invest metabolic energy to upregulate active transport per unit area through CO2 -concentrating mechanisms (CCMs). Previous studies have focused on among-species comparisons, which complicates disentangling the role of cell size from other covarying traits. In this study, we investigated the DIC assimilation of the green alga Dunaliella tertiolecta after using artificial selection to evolve a 9.3-fold difference in cell volume. We compared CO2 affinity, external carbonic anhydrase (CAext ), isotopic signatures (δ13 C) and growth among size-selected lineages. Evolving cells to larger sizes led to an upregulation of CCMs that improved the DIC uptake of this species, with higher CO2 affinity, higher CAext and higher δ13 C. Larger cells also achieved faster growth and higher maximum biovolume densities. We showed that evolutionary shifts in cell size can alter the efficiency of DIC uptake systems to influence the fitness of a phytoplankton species.


Asunto(s)
Anhidrasas Carbónicas , Fitoplancton , Carbono , Dióxido de Carbono , Anhidrasas Carbónicas/metabolismo , Tamaño de la Célula , Fotosíntesis , Fitoplancton/metabolismo
6.
Mol Phylogenet Evol ; 161: 107172, 2021 08.
Artículo en Inglés | MEDLINE | ID: mdl-33813020

RESUMEN

Larger molecular phylogenies based on ever more genes are becoming commonplace with the advent of cheaper and more streamlined sequencing and bioinformatics pipelines. However, many groups of inconspicuous but no less evolutionarily or ecologically important marine invertebrates are still neglected in the quest for understanding species- and higher-level phylogenetic relationships. Here, we alleviate this issue by presenting the molecular sequences of 165 cheilostome bryozoan species from New Zealand waters. New Zealand is our geographic region of choice as its cheilostome fauna is taxonomically, functionally and ecologically diverse, and better characterized than many other such faunas in the world. Using this most taxonomically broadly-sampled and statistically-supported cheilostome phylogeny comprising 214 species, when including previously published sequences, and 17 genes (2 nuclear and 15 mitochondrial) we tested several existing systematic hypotheses based solely on morphological observations. We find that lower taxonomic level hypotheses (species and genera) are robust while our inferred trees did not reflect current higher-level systematics (family and above), illustrating a general need for the rethinking of current hypotheses. To illustrate the utility of our new phylogeny, we reconstruct the evolutionary history of frontal shields (i.e., a calcified body-wall layer in ascus-bearing cheilostomes) and ask if its presence has any bearing on the diversification rates of cheilostomes.


Asunto(s)
Evolución Biológica , Briozoos/clasificación , Briozoos/genética , Filogenia , Animales , Briozoos/anatomía & histología , Nueva Zelanda
7.
Proc Biol Sci ; 287(1933): 20200995, 2020 08 26.
Artículo en Inglés | MEDLINE | ID: mdl-32811317

RESUMEN

Size and metabolism are highly correlated, so that community energy flux might be predicted from size distributions alone. However, the accuracy of predictions based on interspecific energy-size relationships relative to approaches not based on size distributions is unknown. We compare six approaches to predict energy flux in phytoplankton communities across succession: assuming a constant energy use among species (per cell or unit biomass), using energy-size interspecific scaling relationships and species-specific rates (both with or without accounting for density effects). Except for the per cell approach, all others explained some variation in energy flux but their accuracy varied considerably. Surprisingly, the best approach overall was based on mean biomass-specific rates, followed by the most complex (species-specific rates with density). We show that biomass-specific rates alone predict community energy flux because the allometric scaling of energy use with size measured for species in isolation does not reflect the isometric scaling of these species in communities. We also find energy equivalence throughout succession, even when communities are not at carrying capacity. Finally, we discuss that species assembly can alter energy-size relationships, and that metabolic suppression in response to density might drive the allometry of community energy flux as biomass accumulates.


Asunto(s)
Ecosistema , Fitoplancton , Biomasa , Tamaño Corporal , Metabolismo Energético , Modelos Biológicos , Densidad de Población
8.
Phys Rev Lett ; 125(21): 216402, 2020 Nov 20.
Artículo en Inglés | MEDLINE | ID: mdl-33274982

RESUMEN

Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of a chiral crystal. We have studied by spin- and angle-resolved photoelectron spectroscopy its unconventional electronic structure and unique spin texture. We identify Kramers-Weyl, composite, and accordionlike Weyl fermions, so far only predicted by theory, and show that the spin polarization is parallel to the wave vector along the lines in k space connecting high-symmetry points. Our results clarify the symmetries that enforce such spin texture in a chiral crystal, thus bringing new insight in the formation of a spin vectorial field more complex than the previously proposed hedgehog configuration. Our findings thus pave the way to a classification scheme for these exotic spin textures and their search in chiral crystals.

9.
J Endocrinol Invest ; 43(11): 1637-1643, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32300976

RESUMEN

PURPOSE: Type 2 amiodarone-induced thyrotoxicosis (AIT2) is a form of drug-induced destructive thyroiditis, usually treated with oral glucocorticoids (oGCs). Our objective was to investigate the short-term effects of intravenous glucocorticoids (ivGCs) on serum thyroid hormone concentrations in patients with AIT2. METHODS: Exploratory study of three naive AIT2 patients treated with iv methylprednisolone (two pulses of 400 mg with no interpulse oGCs), followed by oGCs, matched 1:3 with AIT2 patients treated with oGCs alone. Changes in serum thyroid hormone concentrations were evaluated in the short-term period (24 h and 7 days) and after a cumulative dosage of 400 and 800 mg equivalents of methylprednisolone; in addition, healing time and duration of exposure to GCs were calculated. RESULTS: During the first 24 h of treatment, serum FT4 concentrations increased in ivGCs patients, and decreased in oGCs patients (+ 3.3% vs - 10.7%, respectively, p = 0.025). After 7 days, serum FT4 and FT3 concentrations decreased significantly in both groups, with no statistical difference between them (p = 0.439 for FT4 and p = 0.071 for FT3), even though the cumulative GCs dose was higher in ivGCs than in oGCs patients (800 mg vs 280 mg, p = 0.008). Furthermore, the iv administration of single 400 mg pulses of methylprednisolone resulted in a less significant decrease in serum thyroid hormone concentrations when compared to equivalent GCs doses fractionated in several consecutive days (p = 0.021 for FT4 and p = 0.052 for FT3). There were no significant differences in the healing time (p = 0.239) and duration of exposure to GCs (p = 0.099). CONCLUSIONS: High-dose ivGCs therapy does not offer advantages over standard oGCs therapy in the rapid, short-term control of AIT2.


Asunto(s)
Amiodarona/efectos adversos , Metilprednisolona/administración & dosificación , Hormonas Tiroideas/sangre , Tirotoxicosis/inducido químicamente , Tirotoxicosis/tratamiento farmacológico , Administración Intravenosa , Adulto , Anciano , Relación Dosis-Respuesta a Droga , Femenino , Glucocorticoides/administración & dosificación , Humanos , Masculino , Persona de Mediana Edad , Proyectos Piloto , Tirotoxicosis/sangre
10.
Ecol Lett ; 22(9): 1407-1416, 2019 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-31206970

RESUMEN

Body size often strongly covaries with demography across species. Metabolism has long been invoked as the driver of these patterns, but tests of causal links between size, metabolism and demography within a species are exceedingly rare. We used 400 generations of artificial selection to evolve a 2427% size difference in the microalga Dunaliella tertiolecta. We repeatedly measured size, energy fluxes and demography across the evolved lineages. Then, we used standard metabolic theory to generate predictions of how size and demography should covary based on the scaling of energy fluxes that we measured. The size dependency of energy remained relatively consistent in time, but metabolic theory failed to predict demographic rates, which varied unpredictably in strength and even sign across generations. Classic theory holds that size affects demography via metabolism - our results suggest that both metabolism and size act separately to drive demography and that among-species patterns may not predict within-species processes.


Asunto(s)
Tamaño de la Célula , Chlorophyceae/metabolismo , Metabolismo Energético , Modelos Biológicos , Biomasa , Chlorophyceae/citología , Densidad de Población
11.
Phys Rev Lett ; 122(21): 217402, 2019 May 31.
Artículo en Inglés | MEDLINE | ID: mdl-31283333

RESUMEN

Zirconium pentatelluride was recently reported to be a 3D Dirac semimetal, with a single conical band, located at the center of the Brillouin zone. The cone's lack of protection by the lattice symmetry immediately sparked vast discussions about the size and topological or trivial nature of a possible gap opening. Here, we report on a combined optical and transport study of ZrTe_{5}, which reveals an alternative view of electronic bands in this material. We conclude that the dispersion is approximately linear only in the a-c plane, while remaining relatively flat and parabolic in the third direction (along the b axis). Therefore, the electronic states in ZrTe_{5} cannot be described using the model of 3D Dirac massless electrons, even when staying at energies well above the band gap 2Δ=6 meV found in our experiments at low temperatures.

12.
Ecol Lett ; 21(1): 54-62, 2018 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-29143436

RESUMEN

Size imposes physiological and ecological constraints upon all organisms. Theory abounds on how energy flux covaries with body size, yet causal links are often elusive. As a more direct way to assess the role of size, we used artificial selection to evolve the phytoplankton species Dunaliella tertiolecta towards smaller and larger body sizes. Within 100 generations (c. 1 year), we generated a fourfold difference in cell volume among selected lineages. Large-selected populations produced four times the energy than small-selected populations of equivalent total biovolume, but at the cost of much higher volume-specific respiration. These differences in energy utilisation between large (more productive) and small (more energy-efficient) individuals were used to successfully predict ecological performance (r and K) across novel resource regimes. We show that body size determines the performance of a species by mediating its net energy flux, with worrying implications for current trends in size reduction and for global carbon cycles.


Asunto(s)
Evolución Biológica , Tamaño Corporal , Tamaño de la Célula , Ecología , Fitoplancton
13.
J Mol Evol ; 86(2): 111-117, 2018 02.
Artículo en Inglés | MEDLINE | ID: mdl-29349600

RESUMEN

A major goal of evolutionary biology is to understand how beneficial mutations translate into increased fitness. Here, we study beneficial mutations that arise in experimental populations of yeast evolved in glucose-rich media. We find that fitness increases are caused by enhanced maximum growth rate (R) that come at the cost of reduced yield (K). We show that for some of these mutants, high R coincides with higher rates of ethanol secretion, suggesting that higher growth rates are due to an increased preference to utilize glucose through the fermentation pathway, instead of respiration. We examine the performance of mutants across gradients of glucose and nitrogen concentrations and show that the preference for fermentation over respiration is influenced by the availability of glucose and nitrogen. Overall, our data show that selection for high growth rates can lead to an enhanced Crabtree phenotype by the way of beneficial mutations that permit aerobic fermentation at a greater range of glucose concentrations.


Asunto(s)
Aptitud Genética , Saccharomyces cerevisiae/crecimiento & desarrollo , Saccharomyces cerevisiae/metabolismo , Evolución Biológica , Etanol/metabolismo , Evolución Molecular , Fermentación/genética , Glucosa/metabolismo , Mutación , Fenotipo , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo
14.
Proc Biol Sci ; 285(1884)2018 08 01.
Artículo en Inglés | MEDLINE | ID: mdl-30068687

RESUMEN

Size determines the rate at which organisms acquire and use resources but it is unclear what size should be favoured under unpredictable resource regimes. Some theories claim smaller organisms can grow faster following a resource pulse, whereas others argue larger species can accumulate more resources and maintain growth for longer periods between resource pulses. Testing these theories has relied on interspecific comparisons, which tend to confound body size with other life-history traits. As a more direct approach, we used 280 generations of artificial selection to evolve a 10-fold difference in mean body size between small- and large-selected phytoplankton lineages of Dunaliella tertiolecta, while controlling for biotic and abiotic variables. We then quantified how body size affected the ability of this species to grow at nutrient-replete conditions and following periods of nitrogen or phosphorous deprivation. Overall, smaller cells showed slower growth, lower storage capacity and poorer recovery from phosphorous depletion, as predicted by the 'fasting endurance hypothesis'. However, recovery from nitrogen limitation was independent of size-a finding unanticipated by current theories. Phytoplankton species are responsible for much of the global carbon fixation and projected trends of cell size decline could reduce primary productivity by lowering the ability of a cell to store resources.


Asunto(s)
Tamaño de la Célula , Chlorophyceae/crecimiento & desarrollo , Chlorophyceae/fisiología , Chlorophyceae/citología , Nitrógeno/metabolismo , Fósforo/metabolismo , Selección Genética
15.
Clin Exp Immunol ; 194(2): 244-252, 2018 11.
Artículo en Inglés | MEDLINE | ID: mdl-30009382

RESUMEN

Several studies have suggested a link between human microbiome and rheumatoid arthritis (RA) development. Porphyromonas gingivalis seems involved in RA initiation and progression, as supported by the high occurrence of periodontitis. In this case-control study, we analysed tongue P. gingivalis presence and quantification in a large healthy and RA cohort. We enrolled 143 RA patients [male/female (M/F) 32/111, mean ± standard deviation (s.d.), age 57·5 ± 19·8 years, mean ± s.d. disease duration 155·9 ± 114·7 months); 36 periodontitis patients (M/F 11/25, mean ± s.d., age 56 ± 9·9 years, mean ± s.d. disease duration 25·5 ± 20·9 months); and 57 patients (M/F 12/45, mean ± s.d., age 61·4 ± 10·9 years, mean ± s.d. disease duration 62·3 ± 66·9 months) with knee osteoarthritis or fibromyalgia. All subjects underwent a standard cytological swab to identify the rate of P. gingivalis/total bacteria by using quantitative real-time polymerase chain reaction. The prevalence of P. gingivalis resulted similarly in RA and periodontitis patients (48·9 versus 52·7%, P = not significant). Moreover, the prevalence of this pathogen was significantly higher in RA and periodontitis patients in comparison with control subjects (P = 0·01 and P = 0·003, respectively). We found a significant correlation between P. gingivalis rate in total bacteria genomes and disease activity score in 28 joints (DAS28) (erythrocyte sedimentation rate) (r = 0·4, P = 0·01). RA patients in remission showed a significantly lower prevalence of P. gingivalis in comparison with non-remission (P = 0·02). We demonstrated a significant association between the percentage of P. gingivalis on the total tongue biofilm and RA disease activity (DAS28), suggesting that the oral cavity microbiological status could play a role in the pathogenic mechanisms of inflammation, leading to more active disease.


Asunto(s)
Artritis Reumatoide/inmunología , Infecciones por Bacteroidaceae/inmunología , Microbiota/inmunología , Periodontitis/inmunología , Porphyromonas gingivalis/fisiología , Lengua/patología , Adulto , Anciano , Artritis Reumatoide/epidemiología , Infecciones por Bacteroidaceae/epidemiología , Biopelículas , Estudios de Casos y Controles , Estudios de Cohortes , Progresión de la Enfermedad , Femenino , Humanos , Italia/epidemiología , Masculino , Persona de Mediana Edad , Prevalencia , Lengua/microbiología
16.
New Phytol ; 219(1): 449-461, 2018 07.
Artículo en Inglés | MEDLINE | ID: mdl-29658153

RESUMEN

Cell size correlates with most traits among phytoplankton species. Theory predicts that larger cells should show poorer photosynthetic performance, perhaps due to reduced intracellular self-shading (i.e. package effect). Yet current theory relies heavily on interspecific correlational approaches and causal relationships between size and photosynthetic machinery have remained untested. As a more direct test, we applied 250 generations of artificial selection (c. 20 months) to evolve the green microalga Dunaliella teriolecta (Chlorophyta) toward different mean cell sizes, while monitoring all major photosynthetic parameters. Evolving larger sizes (> 1500% difference in volume) resulted in reduced oxygen production per chlorophyll molecule - as predicted by the package effect. However, large-evolved cells showed substantially higher rates of oxygen production - a finding unanticipated by current theory. In addition, volume-specific photosynthetic pigments increased with size (Chla+b), while photo-protectant pigments decreased (ß-carotene). Finally, larger cells displayed higher growth performances and Fv /Fm , steeper slopes of rapid light curves (α) and smaller light-harvesting antennae (σPSII ) with higher connectivity (ρ). Overall, evolving a common ancestor into different sizes showed that the photosynthetic characteristics of a species coevolves with cell volume. Moreover, our experiment revealed a trade-off between chlorophyll-specific (decreasing with size) and volume-specific (increasing with size) oxygen production in a cell.


Asunto(s)
Chlorophyceae/citología , Chlorophyceae/fisiología , Fotosíntesis , Fitomejoramiento/métodos , Carbono/metabolismo , Tamaño de la Célula , Clorofila/metabolismo , Luz , Microalgas/citología , Microalgas/fisiología , Pigmentos Biológicos/metabolismo , Células Vegetales
18.
New Phytol ; 235(5): 2129-2137, 2022 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-35635530
19.
Ecology ; 98(12): 3106-3115, 2017 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-28940445

RESUMEN

Many studies examine how body size mediates energy use, but few investigate how size simultaneously regulates energy acquisition. Furthermore, rarely energy fluxes are examined while accounting for the role of biotic and abiotic factors in which they are nested. These limitations contribute to an incomplete understanding of how size affects the transfer of energy through individuals, populations, and communities. Here we characterized photosynthesis-irradiance (P-I) curves and per-cell net-energy use for 21 phytoplankton species spanning across four orders of magnitude of size and seven phyla, each measured across six light intensities and four population densities. We then used phylogenetic mixed models to quantify how body size influences the energy turnover rates of a species, and how this changes across environments. Rate-parameters for the P-I curve and net-energy budgets were mostly highly correlated and consistent with an allometric size-scaling exponent of <1. The energy flux of a cell decreased with population density and increased with light intensity, but the effect of body size remained constant across all combinations of treatment levels (i.e. no size×populationdensity interaction). The negative effect of population density on photosynthesis and respiration is mostly consistent with an active downregulation of metabolic rates following a decrease in per-cell resource availability, possibly as an adaptive strategy to reduce the minimum requirements of a cell and improve its competitive ability. Also, because an increase in body size corresponds to a less-than-proportional increase in net-energy (i.e. exponent<1), we propose that volume-specific net-energy flux can represent an important cost of evolving larger body sizes in autotrophic single-cell organisms.


Asunto(s)
Ecosistema , Fitoplancton , Biomasa , Luz , Fotosíntesis , Filogenia
20.
J Endocrinol Invest ; 45(12): 2407-2408, 2022 12.
Artículo en Inglés | MEDLINE | ID: mdl-35737286
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