Mobile Pool Research Articles

How Could Higher Education System Help Attract International Organisations? Differences Between China, the U.S., Switzerland, and the Netherlands

ABSTRACTAs more regions seek to attract international organisations (IOs) to improve their lack of voice in the global community, researchers have increasingly examined the factors that influence the IO location decisions. While these studies inform policy development, most focus on external factors such as international relations, with limited attention to a city's internal qualities. We reviewed the existing literature systematically to identify the factors that influence the location selection of IOs and deeply discussed the neglected factors as well as how to improve them. We especially explored “talents gathering” factor and analysed what could the higher education system contribute to it. We found out three main influencing factors: economy, government action, and talent gathering, among which the third is the most pivotal one. Specifically, even economically robust regions might lose IOs if political instability or other issues hinder timely payment of dues. Government policies should foster networks to prevent competition between different levels of governance. Additionally, IO tends to have less mobile talent pools compared to other industries, making it harder for these organisations to establish a talent base in new locations. Furthermore, an interesting finding is that higher education may greatly foster building the IO ecosystem within a city. We found that, compared to Western models, Chinese universities lack specialised programs to train professionals for IOs, offer insufficient practical resources, and are unaware of the need to establish employment support systems. These observations highlight the need for decision‐makers of higher education institutions (HEIs) and governments to maximise resources to build the local IO ecosystem and IO employment support system.

Demographic fluctuations in bloodstream Staphylococcus aureus lineages configure the mobile gene pool and antimicrobial resistance

Staphylococcus aureus in the bloodstream causes high morbidity and mortality, exacerbated by the spread of multidrug-resistant and methicillin-resistant S. aureus (MRSA). We aimed to characterize the circulating lineages of S. aureus from bloodstream infections and the contribution of individual lineages to resistance over time. Here, we generated 852 high-quality short-read draft genome sequences of S. aureus isolates from patient blood cultures in a single hospital from 2010 to 2022. A total of 80 previously recognized sequence types (ST) and five major clonal complexes are present in the population. Two frequently detected lineages, ST5 and ST8 exhibited fluctuating demographic structures throughout their histories. The rise and fall in their population growth coincided with the acquisition of antimicrobial resistance, mobile genetic elements, and superantigen genes, thus shaping the accessory genome structure across the entire population. These results reflect undetected selective events and changing ecology of multidrug-resistant S. aureus in the bloodstream.

IS26 and the IS26 family: versatile resistance gene movers and genome reorganizers.

SUMMARYIn Gram-negative bacteria, the insertion sequence IS26 is highly active in disseminating antibiotic resistance genes. IS26 can recruit a gene or group of genes into the mobile gene pool and support their continued dissemination to new locations by creating pseudo-compound transposons (PCTs) that can be further mobilized by the insertion sequence (IS). IS26 can also enhance expression of adjacent potential resistance genes. IS26 encodes a DDE transposase but has unique properties. It forms cointegrates between two separate DNA molecules using two mechanisms. The well-known copy-in (replicative) route generates an additional IS copy and duplicates the target site. The recently discovered and more efficient and targeted conservative mechanism requires an IS in both participating molecules and does not generate any new sequence. The unit of movement for PCTs, known as a translocatable unit or TU, includes only one IS26. TU formed by homologous recombination between the bounding IS26s can be reincorporated via either cointegration route. However, the targeted conservative reaction is key to generation of arrays of overlapping PCTs seen in resistant pathogens. Using the copy-in route, IS26 can also act on a site in the same DNA molecule, either inverting adjacent DNA or generating an adjacent deletion plus a circular molecule carrying the DNA segment lost and an IS copy. If reincorporated, these circular molecules create a new PCT. IS26 is the best characterized IS in the IS26 family, which includes IS257/IS431, ISSau10, IS1216, IS1006, and IS1008 that are also implicated in spreading resistance genes in Gram-positive and Gram-negative pathogens.

Analysis of state 1—state 2 transitions by genome editing and complementation reveals a quenching component independent from the formation of PSI-LHCI-LHCII supercomplex in Arabidopsis thaliana

BackgroundThe light-harvesting antennae of photosystem (PS) I and PSII are pigment-protein complexes responsible of the initial steps of sunlight conversion into chemical energy. In natural environments plants are constantly confronted with the variability of the photosynthetically active light spectrum. PSII and PSI operate in series but have different optimal excitation wavelengths. The prompt adjustment of light absorption by photosystems is thus crucial to ensure efficient electron flow needed to sustain downstream carbon fixing reactions. Fast structural rearrangements equilibrate the partition of excitation pressure between PSII and PSI following the enrichment in the red (PSII-favoring) or far-red (PSI-favoring) spectra. Redox imbalances trigger state transitions (ST), a photoacclimation mechanism which involves the reversible phosphorylation/dephosphorylation of light harvesting complex II (LHCII) proteins by the antagonistic activities of the State Transition 7 (STN7) kinase/TAP38 phosphatase enzyme pair. During ST, a mobile PSII antenna pool associates with PSI increasing its absorption cross section. LHCII consists of assorted trimeric assemblies of Lhcb1, Lhcb2 and Lhcb3 protein isoforms (LHCII), several being substrates of STN7. However, the precise roles of Lhcb phosphorylation during ST remain largely elusive.ResultsWe inactivated the complete Lhcb1 and Lhcb2 gene clades in Arabidopsis thaliana and reintroduced either wild type Lhcb1.3 and Lhcb2.1 isoforms, respectively, or versions lacking N-terminal phosphorylatable residues proposed to mediate state transitions. While the substitution of Lhcb2.1 Thr-40 prevented the formation of the PSI-LHCI-LHCII complex, replacement of Lhcb1.3 Thr-38 did not affect the formation of this supercomplex, nor did influence the amplitude or kinetics of PSII fluorescence quenching upon state 1—state 2 transition.ConclusionsPhosphorylation of Lhcb2 Thr-40 by STN7 alone accounts for ≈ 60% of PSII fluorescence quenching during state transitions. Instead, the presence of Thr-38 phosphosite in Lhcb1.3 was not required for the formation of the PSI-LHCI-LHCII supercomplex nor for re-equilibration of the plastoquinone redox state. The Lhcb2 phosphomutant was still capable of ≈ 40% residual fluorescence quenching, implying that a yet uncharacterized, STN7-dependent, component of state transitions, which is unrelated to Lhcb2 Thr-40 phosphorylation and to the formation of the PSI-LHCI-LHCII supercomplex, contributes to the equilibration of the PSI/PSII excitation pressure upon plastoquinone over-reduction.

An exploratory steady-state redox model of photosynthetic linear electron transport for use in complete modelling of photosynthesis for broad applications.

A photochemical model of photosynthetic electron transport (PET) is needed to integrate photophysics, photochemistry, and biochemistry to determine redox conditions of electron carriers and enzymes for plant stress assessment and mechanistically link sun-induced chlorophyll fluorescence to carbon assimilation for remotely sensing photosynthesis. Towards this goal, we derived photochemical equations governing the states and redox reactions of complexes and electron carriers along the PET chain. These equations allow the redox conditions of the mobile plastoquinone pool and the cytochrome b6 f complex (Cyt) to be inferred with typical fluorometry. The equations agreed well with fluorometry measurements from diverse C3 /C4 species across environments in the relationship between the PET rate and fraction of open photosystem II reaction centres. We found the oxidation of plastoquinol by Cyt is the bottleneck of PET, and genetically improving the oxidation of plastoquinol by Cyt may enhance the efficiency of PET and photosynthesis across species. Redox reactions and photochemical and biochemical interactions are highly redundant in their complex controls of PET. Although individual reaction rate constants cannot be resolved, they appear in parameter groups which can be collectively inferred with fluorometry measurements for broad applications. The new photochemical model developed enables advances in different fronts of photosynthesis research.

Enrofloxacin-induced transfer of multiple-antibiotic resistance genes and emergence of novel resistant bacteria in red swamp crayfish guts and pond sediments.

Antibiotic resistance genes (ARGs) can be transferred from environmental microbes to human pathogens, thus leading to bacterial infection treatment failures. The aquaculture polluted by over-used antibiotics is considered as a notorious reservoir of ARGs. However, the origin, diachronic changes, and mobility of ARGs under antibiotic exposure in aquaculture systems remain elusive. Our findings showed that enrofloxacin application also increased the relative abundance of various ARGs in addition to quinolone-resistance genes and induced ARG dissemination in crayfish gut and sediment bacteria. Further investigation indicated that the transposase-mediated recombination was the major driver of horizontal gene transfer (HGT) of ARGs under antibiotic stress. Notably, enrofloxacin application also induced the generation of some metagenome-assembled genomes (MAGs) carrying multiple ARGs, which were identified as novel species. Additionally, Enterobacteriaceae constituted a mobile ARG pool in aquaculture. Therefore, aquaculture provides potential wide environmental pathways for generation and spread of antibiotic resistance. Our findings of ARG temporal variations and dissemination pattern in aquaculture with artificial use of antibiotics are critical to the management of antibiotic resistance, which is of great ecosystem and health implications.

Metalloallostery and Transition Metal Signaling: Bioinorganic Copper Chemistry Beyond Active Sites.

Transition metal chemistry is essential to life, where metal binding to DNA, RNA, and proteins underpins all facets of the central dogma of biology. In this context, metals in proteins are typically studied as static active site cofactors. However, the emergence of transition metal signaling, where mobile metal pools can transiently bind to biological targets beyond active sites, is expanding this conventional view of bioinorganic chemistry. This Minireview focuses on the concept of metalloallostery, using copper as a canonical example of how metals can regulate protein function by binding to remote allosteric sites (e.g., exosites). We summarize advances in and prospects for the field, including imaging dynamic transition metal signaling pools, allosteric inhibition or activation of protein targets by metal binding, and metal-dependent signaling pathways that underlie nutrient vulnerabilities in diseases spanning obesity, fatty liver disease, cancer, and neurodegeneration.

Metalloallostery and Transition Metal Signaling: Bioinorganic Copper Chemistry Beyond Active Sites

AbstractTransition metal chemistry is essential to life, where metal binding to DNA, RNA, and proteins underpins all facets of the central dogma of biology. In this context, metals in proteins are typically studied as static active site cofactors. However, the emergence of transition metal signaling, where mobile metal pools can transiently bind to biological targets beyond active sites, is expanding this conventional view of bioinorganic chemistry. This Minireview focuses on the concept of metalloallostery, using copper as a canonical example of how metals can regulate protein function by binding to remote allosteric sites (e.g., exosites). We summarize advances in and prospects for the field, including imaging dynamic transition metal signaling pools, allosteric inhibition or activation of protein targets by metal binding, and metal‐dependent signaling pathways that underlie nutrient vulnerabilities in diseases spanning obesity, fatty liver disease, cancer, and neurodegeneration.

Incorporation of a recirculating mobile lipid pool description into the cyclic volatile siloxane (cVMS) PBPK model captures terminal clearance of D4 after repeated inhalation exposure in F344 and SD Rats

The most recent version of the octamethylcyclotetrasiloxane (D4) physiologically based pharmacokinetic (model) was developed using the available kinetic studies in male and female F344 rats. Additional data, which had not been included in the D4 model development, allowed for a more detailed assessment of the loss of D4 following long-term exposure in both SD and F344 rats. This new data demonstrated a deficiency in the published PBPK model predictions of terminal concentrations of D4 in plasma and fat 14 days after the end of exposures for 28-days, 6 h/day, where the model predictions were an order of magnitude lower than the data. To capture this time-point without altering the end-of-exposure peak concentrations in blood and fat required conversion of the one-way (liver to fat) mobile lipoprotein pool (MLP) into a bi-directional pool between liver and fat. Simulation of the D4 pharmacokinetics in the SD rat, as opposed to the F344 rat, also required a reduction of both fold induction of liver metabolism (KMAX: 5- to 2-fold) and maximal rate of metabolism (VMAXC: 5.0–1.54 mg/kg0.75). The revised MLP description was extended to the human D4 model using a parallelogram approach between rat and human MLP parameters to establish the parameters for the current model in the absence of similar long-term clearance data in the human. The revised human D4 model provided good fits to the human inhalation and dermal exposure studies while not appreciably altering cross-species dose metrics based on the free concentration of D4 in blood.

Single chloroplast in folio imaging sheds light on photosystem energy redistribution during state transitions.

Oxygenic photosynthesis is driven by light absorption in photosystem I (PSI) and photosystem II (PSII). A balanced excitation pressure between PSI and PSII is required for optimal photosynthetic efficiency. State transitions serve to keep this balance. If PSII is overexcited in plants and green algae, a mobile pool of light-harvesting complex II (LHCII) associates with PSI, increasing its absorption cross-section and restoring the excitation balance. This is called state 2. Upon PSI overexcitation, this LHCII pool moves to PSII, leading to state 1. Whether the association/dissociation of LHCII with the photosystems occurs between thylakoid grana and thylakoid stroma lamellae during state transitions or within the same thylakoid region remains unclear. Furthermore, although state transitions are thought to be accompanied by changes in thylakoid macro-organisation, this has never been observed directly in functional leaves. In this work, we used confocal fluorescence lifetime imaging (FLIM) to quantify state transitions in single Arabidopsis (Arabidopsis thaliana) chloroplasts in folio with sub-micrometre spatial resolution. The change in excitation-energy distribution between PSI and PSII was investigated at a range of excitation wavelengths between 475 nm and 665 nm. For all excitation wavelengths, the PSI/(PSI + PSII) excitation ratio was higher in state 2 than in state 1. We next imaged the local PSI/(PSI + PSII) excitation ratio for single chloroplasts in both states. The data indicated that LHCII indeed migrates between the grana and stroma lamellae during state transitions. Finally, fluorescence intensity images revealed that thylakoid macro-organisation is largely unaffected by state transitions. This single chloroplast in folio imaging method will help in understanding how plants adjust their photosynthetic machinery to ever-changing light conditions.

Diverse functional genes harboured in extracellular vesicles from environmental and human microbiota.

Exchange of mobile functional genes within microbiota benefits the microbial community. However, the status of the mobile gene pool in environment is still largely unclear, impeding the understanding on the process of gene transfer in natural microbial communities. The release of extracellular vesicles (EVs) by diverse organisms has been proposed to be a vital way in the complex networks of interactions between microbes and their habitats. In this study, we hypothesized that microbial EVs encapsulating functional DNA are widely distributed in the environmental matrix. The prevalence, source and DNA cargoes of EVs in three types of typical microbial habitats were studied. High abundance of EVs comparable to the bacterial concentration was found in human faeces, wastewater and soil. Metagenomic analysis showed the diverse and differential taxonomy of EVs-associated DNA compared to source microbiome. An array of efficient EVs producing species was identified. A wide variety of mobile genes including glycoside hydrolase family 25 were enriched. Antibiotic resistance genes co-localizing with mobile genetic elements were abundant in the EVs. This study provides novel insights into the prevalent EVs as a reservoir for the mobile functional genes in the natural environment.

Genetic diversity and variation in antimicrobial-resistance determinants of non-serotype 2 Streptococcus suis isolates from healthy pigs.

Streptococcus suis is a leading cause of bacterial meningitis in South-East Asia, with frequent zoonotic transfer to humans associated with close contact with pigs. A small number of invasive lineages are responsible for endemic infection in the swine industry, causing considerable global economic losses. A lack of surveillance and a rising trend in clinical treatment failure has raised concerns of growing antimicrobial resistance (AMR) among invasive S. suis . Gene flow between healthy and disease isolates is poorly understood and, in this study, we sample and sequence a collection of isolates predominantly from healthy pigs in Chiang Mai province, Northern Thailand. Pangenome characterization identified extensive genetic diversity and frequent AMR carriage in isolates from healthy pigs. Multiple AMR genes were identified, conferring resistance to aminoglycosides, lincosamides, tetracycline and macrolides. All isolates were non-susceptible to three or more different antimicrobial classes, and 75 % of non-serotype 2 isolates were non-susceptible to six or more classes (compared to 37.5 % of serotype 2 isolates). AMR genes were found on integrative and conjugative elements previously observed in other species, suggesting a mobile gene pool that can be accessed by invasive disease isolates. This article contains data hosted by Microreact.

Genome Evolution of a Symbiont Population for Pathogen Defense in Honeybees.

The honeybee gut microbiome is thought to be important for bee health, but the role of the individual members is poorly understood. Here, we present closed genomes and associated mobilomes of 102 Apilactobacillus kunkeei isolates obtained from the honey crop (foregut) of honeybees sampled from beehives in Helsingborg in the south of Sweden and from the islands Gotland and Åland in the Baltic Sea. Each beehive contained a unique composition of isolates and repeated sampling of similar isolates from two beehives in Helsingborg suggests that the bacterial community is stably maintained across bee generations during the summer months. The sampled bacterial population contained an open pan-genome structure with a high genomic density of transposons. A subset of strains affiliated with phylogroup A inhibited growth of the bee pathogen Melissococcus plutonius, all of which contained a 19.5 kb plasmid for the synthesis of the antimicrobial compound kunkecin A, while a subset of phylogroups B and C strains contained a 32.9 kb plasmid for the synthesis of a putative polyketide antibiotic. This study suggests that the mobile gene pool of A. kunkeei plays a key role in pathogen defense in honeybees, providing new insights into the evolutionary dynamics of defensive symbiont populations.

Dumpster Diving: Aquatic Leisure, DIY Aesthetics, and Performance of Public Space in Macro Sea’s Mobile Pools

In August 2010, as part of Summer Streets, a citywide initiative to celebrate “New York City’s most valuable public space [its streets],” the Department of Transportation installed three mobile pools, made from dumpsters, on Park Avenue between 40th and 41st streets. The choice of dumpster swimming pools as keystone attractions for 2010 Summer Streets is not only testament to the need for a summer cool-down but also participates in the long history that public pools have played in urban planning as markers of a community’s health and well-being. Through tracing the mobile pools’ connections to the Do-It-Yourself (DIY)-aesthetic practice and public swimming pool history, I argue that although the dumpster pools were intended as a popular intervention to reconfigure socio-spatial relationships, the effectiveness of that intervention was varied. The pools recapitulated notions of private leisure and failed to participate in the actual city surroundings—allowing privileged participants to perform an ethical commitment to re-use and public good without promoting change for the actual communities in need.

Could ammonium nutrition increase plant C-sink strength under elevated CO2 conditions?

Atmospheric carbon dioxide (CO2) is increasing, and this affects plant photosynthesis and biomass production. Under elevated CO2 conditions (eCO2), plants need to cope with an unbalanced carbon-to-nitrogen ratio (C/N) due to a limited C sink strength and/or the reported constrains in leaf N. Here, we present a physiological and metabolic analysis of ammonium (NH4+)-tolerant pea plants (Pisum sativum L., cv. snap pea) grown hydroponically with moderate or high NH4+ concentrations (2.5 or 10 mM), and under two atmospheric CO2 concentrations (400 and 800 ppm). We found that the photosynthetic efficiency of the NH4+ tolerant pea plants remain intact under eCO2 thanks to the capacity of the plants to maintain the foliar N status (N content and total soluble proteins), and the higher C-skeleton requirements for NH4+ assimilation. The capacity of pea plants grown at 800 ppm to promote the C allocation into mobile pools of sugar (mainly sucrose and glucose) instead of starch contributed to balancing plant C/N. Our results also support previous observations: plants exposed to eCO2 and NH4+ nutrition can increase of stomatal conductance. Considering the C and N source-sink balance of our plants, we call for exploring a novel trait, combining NH4+ tolerant plants with a proper NH4+ nutrition management, as a way for a better exploitation of eCO2 in C3 crops.

Sediment phosphorus mobility in Võrtsjärv, a large shallow lake: Insights from phosphorus sorption experiments and long-term monitoring

Sediment phosphorus (P) recycling is one of the key issues in lake water quality management. We studied sediment P mobility in Võrtsjärv, a large shallow lake in Estonia using both sorption experiments and long-term (1985–2020) monitoring data of the lake. Over the years studied, the lake has undergone a decline in external phosphorus loading (EL), while no improvement in phytoplankton indicators was observed.The results of the sorption experiments revealed that it may be successfully used as a tool to determine P forms involved in P retention, as up to 100% of the P from the water column was detected in sediments. Incubation of wet sediment is preferred to dry because of the sensitivity of organic P to desiccation. In the sediments of Võrtsjärv, the labile P (Lab-P) and iron bound (Fe-P) fractions are the major forms of the mobile pool that supply internal P load as sediment released P. The internal P load calculated from summer total P (TP) increases (ILin situ) in the water column was on average 42%, but could reach 240% of EL at extreme environmental conditions. ILin situ was correlated with the active area, which resembles the area involved in redox-related P release in polymictic lakes, and with the mean bottom shear stress in summer. ILin situ showed a similar decreasing pattern as the external P load over the years 1985–2020, and was likely driven by the decrease of the pool of releasable P. Similarly, the decreases in sediment loading by P retention in our P sorption experiment were associated with decreases in the concentration of the potentially mobile P forms (mainly Lab-P and Fe-P). These results show that changes in external P loading can successfully control internal P loading and are useful in water quality management of large lakes.

Dynamic evolution of a secondary turbidity maximum under various forcing conditions in a microtidal estuary

Axial survey and in situ mooring in microtidal Masan Bay were conducted to reveal the mechanism for movement of secondary turbidity maximum (STM) and sediment resuspension. The Bay is characterized by sluggish water circulation with a vertically well-mixed water column. The strength of the residual estuarine current (Δu¯) was enhanced by the combined effects of decreased tidal currents, increased precipitation, and down-estuary (northerly) winds, whereas Δu¯ was weakened by increased tidal currents and up-estuary (southerly) winds. The variability of current asymmetry originated from Δu¯ contributed to the entrapment of suspended sediments, creating a mobile sediment pool in central regions of the Bay. The sediments resuspended from the mobile sediment pool were more influenced by residual currents than the tidal currents, and they remained in suspension near bed. When the down-estuary winds were applied to the mobile sediment pool, the near-bed sediments were readily resuspended to form an STM > 40 mg l−1. The STM moved up-estuary by persistent high Δu¯ and down-estuary by an intermittent low Δu¯. Over the entire measurement periods, the STM moved by at least 450 m toward the up-estuary. As the consolidated sediment layer was exposed by the movement of the STM, near-bed currents were ineffective in resuspending sediments from the consolidated layer even though the winds provided sufficient current strength. Due to the depletion of available sediments for resuspension, the STM was not fully generated. This study highlights that the STM in a microtidal estuary can be determined by the combined function of various forcings such as tide, wind, and precipitation.

Структурная энтропия как мера фракционирования массопотоков в экосистемах в условиях транспортного прессинга

The features of the distribution of polycyclic aromatic hydrocarbons considered as geochemical markers of mass transfer in the structural transitions of «snow–soil–plants» of urban soil-plant systems are analyzed. The expe-rimental impact test site is an area with an intensive transport press – the RUDN campus with an adjacent green zone (south–western district of Moscow). Spatial variability of polyarenes in media and structural transitions is chaotic. Cal-culations of polyarene emissions from fuel combustion, tire abrasion, brake pads and asphalt have been carried out. Such an «overlay» of pollution from external sources contributes to the intensive chaoticization of structural transitions in the designated system. The role of extensive parameters (entropy increments, Gibbs energy, enthalpy) in media and various structural transitions is estimated. The wave nature of the impact of motor vehicles as sources of pollution is emphasized. Informative parameters of the fractionation of the polyarene complex are the dependences of the increment of structural entropy on the translocation coefficients in the interacting components. The thermodynamic apparatus makes it possible to identify the factors and mechanisms that determine the accumulation of polyarenes in natural and transport-loaded conditions. Mobile and neutral pools of migrating polyarenes in the soil-plant system were identified by grouping methods. The analysis of migration in the nonequilibrium system «snow–soil–plant roots – stems» using the principles of thermodynamics revealed the chaotic processes of migration and accumulation. The leading role in the structuring of polyarene flows in the above system is assigned to the rhizosphere. Based on the variability of thermody-namic parameters, the concept of structural flowability of systems is introduced. The introduction of the concept makes it possible to objectify the procedure for assessing the intensity of anthropogenic loads and to identify areas of the soil-plant system with maximum accumulation and with maximum «throughput» in relation to polyarenes.

Combining spectroscopic and flux measurement techniques to determine solid-phase speciation and solubility of phosphorus in agricultural soils

Soil solid-phase phosphorus (P) speciation and chemical conditions exert a crucial role in both aqueous P speciation and concentration—the most available and mobile pool for biota in environments. However, the interplay between solid-phase speciation and the aqueous phase of P in soil systems is unresolved. Herein, we investigated the speciation and solubility of P in tropical agricultural soils, which are often poor in P availability. Phosphorus K-edge X-ray absorption near edge structure (XANES) spectra of acidic soils identified dominant Al-hydroxide-phosphates (∼58%: P adsorbed to gibbsite 19%, P adsorbed to kaolinite 14%, and variscite 16%), followed by Fe-hydroxide-phosphates (∼36%: P adsorbed to ferrihydrite 14% and strengite 22%), and trace organic P (∼6%). Calcium phosphates (∼52%) prevailed in the alkaline/calcareous soils with moderate and minor contributions from Al-phosphates (∼37%: P adsorbed to kaolinite 28%, P adsorbed to gibbsite 1%, and variscite 7%) and Fe phosphate (∼11%), respectively. The time-averaged P concentration in the aqueous phase using diffusive gradients in thin films (CDGT) was highly variable from 4 to 123 μg P L–1, with the highest and the lowest values observed in acidic-coarse- and alkaline-fine-textured soils, respectively. The CDGT concentration was positively related to belowground P uptake. The CDGT concentration had negative relationships with pH, Ca-P XANES, and total and extractable Ca, indicating that Ca phosphates were the primary constituents decreasing the dissolvable P concentration. This study highlighted the importance of solid-phase P species in determining P fluxes and is relevant to diverse soils rich in Fe/Al/Ca compounds under extremely acidic to alkaline conditions.

The role of light-harvesting complex I in excitation energy transfer from LHCII to photosystem I in Arabidopsis.

Photosynthesis powers nearly all life on Earth. Light absorbed by photosystems drives the conversion of water and carbon dioxide into sugars. In plants, photosystem I (PSI) and photosystem II (PSII) work in series to drive the electron transport from water to NADP+. As both photosystems largely work in series, a balanced excitation pressure is required for optimal photosynthetic performance. Both photosystems are composed of a core and light-harvesting complexes (LHCI) for PSI and LHCII for PSII. When the light conditions favor the excitation of one photosystem over the other, a mobile pool of trimeric LHCII moves between both photosystems thus tuning their antenna cross-section in a process called state transitions. When PSII is overexcited multiple LHCIIs can associate with PSI. A trimeric LHCII binds to PSI at the PsaH/L/O site to form a well-characterized PSI–LHCI–LHCII supercomplex. The binding site(s) of the “additional” LHCII is still unclear, although a mediating role for LHCI has been proposed. In this work, we measured the PSI antenna size and trapping kinetics of photosynthetic membranes from Arabidopsis (Arabidopsis thaliana) plants. Membranes from wild-type (WT) plants were compared to those of the ΔLhca mutant that completely lacks the LHCI antenna. The results showed that “additional” LHCII complexes can transfer energy directly to the PSI core in the absence of LHCI. However, the transfer is about two times faster and therefore more efficient, when LHCI is present. This suggests LHCI mediates excitation energy transfer from loosely bound LHCII to PSI in WT plants.