Biogenic Phosphonate Utilization by Globally Distributed Diatom Thalassiosira pseudonana.

Phosphonates are a class of organic phosphorus (P) compounds that contribute ~25% of dissolved organic P. Recent studies reveal the important role of phosphonates mediated by prokaryotes in the marine P redox cycle. However, its bioavailability by eukaryotic phytoplankton is under debate. 2-Aminoethylphosphonic acid (2-AEP) and 2-amino-3-phosphonopropionic acid (2-AP3) are two biogenic phosphonates in the marine environment. Here, Thalassiosira pseudonana, a common diatom species in the ocean, is able to recover growth from P starvation when provided with 2-AEP and 2-AP3. Moreover, 2-AEP cultures exhibited a more similar growth rate at 12 °C than at 25 °C when compared with inorganic P cultures. The cellular stoichiometry of 2-AEP groups was further determined, the values of which are in-between the P-depleted and DIP-replete cultures. This study provides evidence that biogenic phosphonates could be adopted as alternative P sources to support diatom growth and may provide physiological adaptation.

Transcriptomic-Guided Phosphonate Utilization Analysis Unveils Evidence of Clathrin-Mediated Endocytosis and Phospholipid Synthesis in the Model Diatom, Phaeodactylum tricornutum.

Phosphonates are important components of marine organic phosphorus, but their bioavailability and catabolism by eukaryotic phytoplankton remain enigmatic. Here, diatom Phaeodactylum tricornutum was used to investigate the bioavailability of phosphonates and describe the underlying molecular mechanism. The results showed that 2-aminoethylphosphonic acid (2-AEP) can be utilized as an alternative phosphorus source. Comparative transcriptomics revealed that the utilization of 2-AEP comprised 2 steps, including molecular uptake through clathrin-mediated endocytosis and incorporation into the membrane phospholipids in the form of diacylglyceryl-2-AEP (DAG-2-AEP). In the global ocean, we found the prevalence and dynamic expression pattern of key genes that are responsible for vesicle formation (CLTC, AP-2) and DAG-AEP synthesis (PCYT2, EPT1) in diatom assemblages. This study elucidates a distinctive mechanism of phosphonate utilization by diatoms, and discusses the ecological implications. IMPORTANCE Phosphonates contribute ~25% of total dissolved organic phosphorus in the ocean, and are found to be important for marine phosphorus biogeochemical cycle. As a type of biogenic phosphonate produced by microorganisms, 2-aminoethylphosphonic acid (2-AEP) widely exists in the ocean. It is well known that 2-AEP can be cleaved and utilized by prokaryotes, but its ability to support the growth of eukaryotic phytoplankton remains unclear. Our research identified the bioavailability of 2-AEP for the diatom Phaeodactylum tricornutum, and proposed a distinctive metabolic pathway of 2-AEP utilization. Different from the enzymatic hydrolysis of phosphonates, the results suggested that P. tricornutum utilizes 2-AEP by incorporating it into phospholipid instead of cleaving the C-P bond. Moreover, the ubiquitous distribution of associated representative gene transcripts in the environmental assemblages and the higher gene transcript abundance in the cold regions were observed, which suggests the possible environmental adaption of 2-AEP utilization by diatoms.

Understanding "Internet Plus Healthcare" in China: Policy Text Analysis.

BACKGROUND: The combination of the internet and healthcare has excellent benefits and far-reaching positive effects in improving service efficiency and promoting social equity. The role of the "internet plus healthcare" (IPHC) has been recognized, especially during the COVID-19 pandemic. This new healthcare model is also familiar to people and shows a bright prospect. OBJECTIVE: This article seeks to accurately understand and fully grasp the characteristics of IPHC policies that can enlighten the formulation of future policies. METHODS: The content analysis method was used to analyze China's IPHC policies collected from the Beida Fabao database and several official websites. RESULTS: We found that the development of IPHC policy has gone through 4 stages and is currently entering a phase of rapid development. IPHC policymakers are primarily health administrative departments. In addition, policy instruments are classified into either supply, environment, or demand, and policy themes can be summarized into 4 categories: facilities, technology, service, and management. CONCLUSIONS: China's IPHC policy has good prospects from the perspective of development trends. The health administrative departments mainly lead the development of China's IPHC policy. It is suggested that these departments involve other stakeholders (ie, medical workers, medical industries, and technology sectors) in formulating policies. Policies prefer to use supply-based and environment-based policy instruments. The policy themes emphasize improving infrastructure construction and high-quality diagnostic and treatment services, strengthening the supporting role of information technology, and ensuring all stakeholders understand their responsibilities.

Spectrophotometric determination of pH and carbonate ion concentrations in seawater: Choices, constraints and consequences.

Accurate and precise marine CO2 system measurements are important for marine carbon cycle research and investigations of ocean acidification. Seawater pH is important because it can be used to characterize a wide range of chemical and biogeochemical processes. Saturation states of calcium carbonate minerals, which are directly proportional to carbonate ion concentration ([CO32-]), influence biogenic calcification and rates of carbonate dissolution. Spectrophotometric pH and carbonate ion measurements can both benefit greatly from the high sensitivity, stability, consistency and processing speed made possible through automation. Spectrophotometric methods are well-suited for shipboard, underway and in situ deployments under harsh conditions. Spectrophotometric pH measurements typically have a reproducibility of 0.0004-0.001 for shipboard and laboratory measurements and 0.0014-0.004 for in situ measurements. Shipboard spectrophotometric measurements of [CO32-] are becoming common on research expeditions. This review highlights the development of methods and instrumentation for spectrophotometric pH and [CO32-] measurements, and discusses the pros and cons of current technology. A comprehensive summary of the analytical merits of different flow analysis instruments is given. Aspects of measurement protocols that bear on the quality of pH and [CO32-] measurements, such as indicator purification, sample pretreatment, etc., are also described. Based on three decades of experience with seawater analysis, this review includes method recommendations and perspectives directly applicable or potentially applicable to pH and [CO32-] analysis of seawater.

High-frequency underway analysis of ammonium in coastal waters using an integrated syringe-pump-based environmental-water analyzer (iSEA).

Accurate methods and related robust analytical instruments for sensitive shipboard determination of ammonium in coastal waters are highly desirable for both oceanographers and environmental scientists. In this study, a multipurpose integrated syringe-pump-based environmental-water analyzer (iSEA) was combined with an on-line filtration system for underway analysis of ammonium in coastal areas. The chemistry is based on a modified indophenol method using o-phenylphenol. The effects of reagent concentrations and sample temperatures were evaluated. The detection limit was 0.15 µM with a 3-cm Z-flow cell, and the linearity was as high as 200 µM. The relative standard deviations at different concentrations (2, 10, and 20 µM) were 2.2%, 0.33%, 0.32% (n = 11). For n = 288 and without any stoppage during repeated analysis for 24 h, the relative standard deviation was 0.85%. The sample throughput was 12 h-1. The effects of salinity and five organic nitrogen compounds were evaluated and showed no interference using the proposed protocol for ammonium analysis. Between results obtained by reference and the present methods, there were no significant differences in the measurements of reference materials and different aqueous samples (n = 51). The analyzers worked well in the transect of 420 km during 7 cruises. A total of 716 analyses were performed automatically on board, demonstrating the capability of iSEA in automated real-time mapping of ammonium distribution in a shipboard laboratory.