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Science论文导读 1208

时间: 2017年12月20日 | 作者: admin | 来源: 未知
Science 20171208 1 【社科】 Designing river flows to improve food security futures in the Lower Mekong Basin 设计湄公河下游盆地地区的河流以改善食品安全的未来前景 J. L. Sabo,et al. http://science.sciencemag.org/

Science 20171208

 

1 【社科】Designing river flows to improve food security futures in the Lower Mekong Basin

设计湄公河下游盆地地区的河流以改善食品安全的未来前景

J. L. Sabo,et al.

http://science.sciencemag.org/content/358/6368/eaao1053

 

(导读 葛鹏)河流的水力发电为清洁能源带来了无与伦比的机会,但人们对于水坝建设给由河流保障的食品安全带来的潜在影响还知之甚少。在热带地区的河流中,降雨带来的周期性洪水脉冲驱动鱼类生产并为全世界超过1.5亿人提供营养。水电工程会改变此类洪水脉冲,从而威胁食品安全。研究通过定义湄公河洪水脉冲的方差分量来预测世界上最大的淡水渔场之一的产量。控制流量方差所需的部分可以提升湄公河下游粮食系统的效率。

 

Rivers provide unrivaled opportunity for clean energy via hydropower, but little is known about the potential impact of dam-building on the food security these rivers provide. In tropical rivers, rainfall drives a periodic flood pulse fueling fish production and delivering nutrition to more than 150 million people worldwide. Hydropower will modulate this flood pulse, thereby threatening food security. We identified variance components of the Mekong River flood pulse that predict yield in one of the largest freshwater fisheries in the world. We used these variance components to design an algorithm for a managed hydrograph to explore future yields. This algorithm mimics attributes of discharge variance that drive fishery yield: prolonged low flows followed by a short flood pulse. Designed flows increased yield by a factor of 3.7 relative to historical hydrology. Managing desired components of discharge variance will lead to greater efficiency in the Lower Mekong Basin food system.

 

2 【计算机】A generative vision model that trains with high data efficiency and breaks text-based CAPTCHAs

一种高数据效率的生成视觉模型攻破基于文本的CAPTCHA验证码

Dileep George   et.al

http://science.sciencemag.org/content/358/6368/eaag2612

 

(导读 雷鸣)本文介绍了一种视觉的概率生成模型,以基于信息传输的推理方式统一进行识别、分割、推断。结果表明,本模型展示出卓越的泛化和封闭推理能力,在场景文本识别基准的数据效率方面比深度神经网络高出300倍,彻底攻破了广泛用于互联网的CAPTCHA验证码防护系统。

 

Learning from a few examples and generalizing to markedly different situations are capabilities of human visual intelligence that are yet to be matched by leading machine learning models. By drawing inspiration from systems neuroscience, we introduce a probabilistic generative model for vision in which message-passing–based inference handles recognition, segmentation, and reasoning in a unified way. The model demonstrates excellent generalization and occlusion-reasoning capabilities and outperforms deep neural networks on a challenging scene text recognition benchmark while being 300-fold more data efficient. In addition, the model fundamentally breaks the defense of modern text-based CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) by generatively segmenting characters without CAPTCHA-specific heuristics. Our model emphasizes aspects such as data efficiency and compositionality that may be important in the path toward general artificial intelligence.

 

3 【生物】Plant RuBisCo assembly in E. coli with five chloroplast chaperones including BSD2

植物RuBisCoBSD25个叶绿体伴侣蛋白在大肠杆菌中的组装

H. Aigner*, R. H. Wilson   et.al

http://science.sciencemag.org/content/358/6368/1272

 

(导读 阿金)植物RuBisCo在光合作用中催化CO2固定,但遗传操作受其在细菌宿主中表达失败的阻碍。本研究通过共同表达包括BSD2在内的多个叶绿体伴侣蛋白,实现拟南芥RuBisCo在大肠杆菌中的功能表达。其中BSD2可稳定RuBisCo8个大亚基终态组装中间体。该成果有助于通过诱变改进RuBisCo酶的功能。

 

Plant RuBisCo, a complex of eight large and eight small subunits, catalyzes the fixation of CO2 in photosynthesis. The low catalytic efficiency of RuBisCo provides strong motivation to reengineer the enzyme with the goal of increasing crop yields. However, genetic manipulation has been hampered by the failure to express plant RuBisCo in a bacterial host. We achieved the functional expression of Arabidopsis thaliana RuBisCo in Escherichia coli by coexpressing multiple chloroplast chaperones. These include the chaperonins Cpn60/Cpn20, RuBisCo accumulation factors 1 and 2, RbcX, and bundle-sheath defective-2 (BSD2). Our structural and functional analysis revealed the role of BSD2 in stabilizing an end-state assembly intermediate of eight RuBisCo large subunits until the small subunits become available. The ability to produce plant RuBisCo recombinantly will facilitate efforts to improve the enzyme through mutagenesis.

 

4 【生物】Structure of the yeast spliceosomal postcatalytic P complex

解析酵母剪接体后催化P复合体的结构

Shiheng Liu, Xueni Li  et.al

http://science.sciencemag.org/content/358/6368/1278

 

(导读 郭怿暄)目前对于RNA剪切中3剪切位点识别机制我们知之甚少。本研究利用冷冻电镜解析了剪切体后催化P复合体的结构,发现3剪切位点主要通过非沃森克里克碱基配对与5剪切位点和剪切分支位点配对,一种或多种蛋白质与P复合体结合,维持3外显子的稳定,并调节解旋酶Prp22的功能,Prp22与特定核苷酸结合完成对3剪切位点的校对和外显子的释放。

 

The spliceosome undergoes dramatic changes in a splicing cycle. Structures of B, Bact, C, C*, and intron lariat spliceosome complexes revealed mechanisms of 5′–splice site (ss) recognition, branching, and intron release, but lacked information on 3′-ss recognition, exon ligation, and exon release. Here we report a cryo–electron microscopy structure of the postcatalytic P complex at 3.3-angstrom resolution, revealing that the 3′ ss is mainly recognized through non–Watson-Crick base pairing with the 5′ ss and branch point. Furthermore, one or more unidentified proteins become stably associated with the P complex, securing the 3′ exon and potentially regulating activity of the helicase Prp22. Prp22 binds nucleotides 15 to 21 in the 3′ exon, enabling it to pull the intron-exon or ligated exons in a 3′ to 5′ direction to achieve 3′-ss proofreading or exon release, respectively.

 

5 【生物】Postcatalytic spliceosome structure reveals mechanism of 3′–splice site selection

后催化剪接体结构揭示了3'剪接位点选择的机制

Max E. Wilkinson  et.al

http://science.sciencemag.org/content/358/6368/1283

 

(导读 郭怿暄)真核细胞剪切体通过两步酯基转移反应将内含子去除,但3剪切位点在外显子连接过程中的识别尚不清楚。本研究通过冷冻电镜解析酵母外显子连接后P复合体剪接体结构。发现3剪切位点AG5剪切位点及剪切分支位点的A通过非沃森克里克碱基配对识别。分支反应后蛋白质因子重塑剪切体,使其结构有助于3剪切位点对接,从而促进外显子连接。

 

Introns are removed from eukaryotic messenger RNA precursors by the spliceosome in two transesterification reactions—branching and exon ligation. The mechanism of 3′–splice site recognition during exon ligation has remained unclear. Here we present the 3.7-angstrom cryo–electron microscopy structure of the yeast P-complex spliceosome immediately after exon ligation. The 3′–splice site AG dinucleotide is recognized through non–Watson-Crick pairing with the 5′ splice site and the branch-point adenosine. After the branching reaction, protein factors work together to remodel the spliceosome and stabilize a conformation competent for 3′–splice site docking, thereby promoting exon ligation. The structure accounts for the strict conservation of the GU and AG dinucleotides at the 5′ and 3′ ends of introns and provides insight into the catalytic mechanism of exon ligation.

 

6 【物理】Attosecond-resolved photoionization of chiral molecules

手性分子在阿秒量级分辨率下的光电离

S. Beaulieu,et al.

http://science.sciencemag.org/content/358/6368/1288

 

(导读 葛鹏)对手性光与物质相互作用的研究使得许多用于辨别对映体的手性光学过程予以发现。本研究实现了使用自校准阿秒光电子干涉测量由圆偏振激光脉冲激发莰酮光电离发射的前向和后向电子波包的时间分布。通过自电离态发射的电子波包时间形态不对称,进一步揭示了强相关电子动力学的手性性质。

 

Chiral light-matter interactions have been investigated for two centuries, leading to the discovery of many chiroptical processes used for discrimination of enantiomers. Whereas most chiroptical effects result from a response of bound electrons, photoionization can produce much stronger chiral signals that manifest as asymmetries in the angular distribution of the photoelectrons along the light-propagation axis. We implemented self-referenced attosecond photoelectron interferometry to measure the temporal profile of the forward and backward electron wave packets emitted upon photoionization of camphor by circularly polarized laser pulses. We measured a delay between electrons ejected forward and backward, which depends on the ejection angle and reaches 24 attoseconds. The asymmetric temporal shape of electron wave packets emitted through an autoionizing state further reveals the chiral character of strongly correlated electronic dynamics.

 

7 【材料】Coherently aligned nanoparticles within a biogenic single crystal: A biological prestressing strategy

在生物单晶内连贯排列纳米颗粒:生物预应力策略

Iryna Polishchuk1,*, Avigail Aronhime Bracha1 et.al

http://science.sciencemag.org/content/358/6368/1294

 

(导读 甜甜)与合成材料相比,生物体产生的材料在一定环境中生成且可选择的元素有限。然而,生命有机体显示出了获得特定功能的策略。为了强化和韧化方解石光学镜头,本研究提出了抗菌素疗法。该过程利用连贯的纳米沉淀物引发主体基质的压应力。作者相信,这些方解石纳米颗粒,在从无定型态转变为结晶态的过程中或之后会发生分离。

 

In contrast to synthetic materials, materials produced by organisms are formed in ambient conditions and with a limited selection of elements. Nevertheless, living organisms reveal elegant strategies for achieving specific functions, ranging from skeletal support to mastication, from sensors and defensive tools to optical function. Using state-of-the-art characterization techniques, we present a biostrategy for strengthening and toughening the otherwise brittle calcite optical lenses found in the brittlestar Ophiocoma wendtii. This intriguing process uses coherent nanoprecipitates to induce compressive stresses on the host matrix, functionally resembling the Guinier–Preston zones known in classical metallurgy. We believe that these calcitic nanoparticles, being rich in magnesium, segregate during or just after transformation from amorphous to crystalline phase, similarly to segregation behavior from a supersaturated quenched alloy.

 

8 【物理】A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni

天鹅座V404黑洞双星系统晕冕的磁场进行精确测量

Yigit Dallilar1,*, Stephen S. Eikenberry   et.al

http://science.sciencemag.org/content/358/6368/1299

 

(导读 阿金)包含吸积黑洞或中子星的双星系统通常会伴随高能量的x射线发射,但对其物理模型的限制条件尚未了结。本研究使用同步红外线、光学、X射线望远镜采集天鹅座V404黑洞系统于2015年爆发后快速冷却事件数据,精确测得其晕冕磁场强度为461±12 Gs,低于预估数据。研究结果有助于了解对黑洞和中子星双星系统中物质吸积物理模型的限制。

 

Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kilo–electron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems.

 

9 【物理】Imaging resonant dissipation from individual atomic defects in graphene

石墨烯中单个原子缺陷的共振耗散图像化

Dorri Halbertal1,*, Moshe Ben Shalom  et.al

http://science.sciencemag.org/content/358/6368/1303

 

(导读 阿金)电-热转化过程中能量耗散的微观过程难以直接观测。本研究使用亚微开尔文扫描纳米测温法实现了石墨烯中来自个别原子尺度缺陷的声子发射的可视化和控制。研究发现当费米能级与缺陷态发生共振时,电子-声子冷却功率能谱出现尖锐峰值,从而揭示主要耗散机制。研究结果使得对纳米尺度上的热量耗散进行控制成为可能。

 

Conversion of electric current into heat involves microscopic processes that operate on nanometer length scales and release minute amounts of power. Although central to our understanding of the electrical properties of materials, individual mediators of energy dissipation have so far eluded direct observation. Using scanning nanothermometry with submicrokelvin sensitivity, we visualized and controlled phonon emission from individual atomic-scale defects in graphene. The inferred electron-phonon “cooling power spectrum” exhibits sharp peaks when the Fermi level comes into resonance with electronic quasi-bound states at such defects. Rare in the bulk but abundant at graphene’s edges, switchable atomic-scale phonon emitters provide the dominant dissipation mechanism. Our work offers insights for addressing key materials challenges in modern electronics and enables control of dissipation at the nanoscale.

 

10 【化学】Renewable acrylonitrile production

可再生丙烯腈(ACN)的生产

Eric M. Karp, Todd R. Eaton, Violeta Sànchez i Nogué, Vassili Vorotnikov  et.al

http://science.sciencemag.org/content/358/6368/1307

 

导读 阿金ACN是用在树脂、碳纤维等中的一种石油衍生化合物。本研究展示使用3-羟基丙酸(3-HP)生产可再生ACN的新方法。通过用廉价的二氧化钛固体酸催化剂脱水和氨氮化从3-羟基丙酸乙酯获得超过90%的ACN摩尔收率。这种吸热方法消除失控危险,提高工艺安全性并减少产品处理要求。

 

Acrylonitrile (ACN) is a petroleum-derived compound used in resins, polymers, acrylics, and carbon fiber. We present a process for renewable ACN production using 3-hydroxypropionic acid (3-HP), which can be produced microbially from sugars. The process achieves ACN molar yields exceeding 90% from ethyl 3-hydroxypropanoate (ethyl 3-HP) via dehydration and nitrilation with ammonia over an inexpensive titanium dioxide solid acid catalyst. We further describe an integrated process modeled at scale that is based on this chemistry and achieves near-quantitative ACN yields (98 ± 2%) from ethyl acrylate. This endothermic approach eliminates runaway reaction hazards and achieves higher yields than the standard propylene ammoxidation process. Avoidance of hydrogen cyanide as a by-product also improves process safety and mitigates product handling requirements.

 

11 【物理】Quantized chiral edge conduction on domain walls of a magnetic topological insulator

磁性拓扑绝缘体畴壁上的量子化手性边缘传导

K. Yasuda et.al

http://science.sciencemag.org/content/358/6368/1311

 

(导读 阿金)畴壁(DW)构型和运动的控制可以实现磁性和介电材料在微小外部磁场下的非易失响应。本研究利用磁力显微镜尖端设计并制造出在量子反常霍尔态中的磁畴,通过输运测量证明了沿指定DW的手性一维边缘传导的存在。研究结果可促进实现低功耗的自旋电子器件。

 

Electronic ordering in magnetic and dielectric materials forms domains with different signs of order parameters. The control of configuration and motion of the domain walls (DWs) enables nonvolatile responses against minute external fields. Here, we realize chiral edge states (CESs) on the magnetic DWs of a magnetic topological insulator. We design and fabricate the magnetic domains in the quantum anomalous Hall state with the tip of a magnetic force microscope and prove the existence of the chiral one-dimensional edge conduction along the prescribed DWs through transport measurements. The proof-of-concept devices based on reconfigurable CESs and Landauer-Büttiker formalism are realized for multiple-domain configurations with well-defined DW channels. Our results may lead to the realization of low-power-consumption spintronic devices.

 

12 【物理】Signatures of exciton condensation in a transition metal dichalcogenide

过渡金属硫族化合物中激子凝聚的特征

Anshul Kogar et.al

http://science.sciencemag.org/content/358/6368/1314

 

(导读 阿金)理论预测激子作为一种玻色子会在超流体或绝缘电子晶体中发生凝聚。本研究使用动量分辨电子能量损失谱仪(M-EELS)研究过渡金属硫族化物半金属1T‐TiSe2中的电子集合模式。研究发现接近相变温度后电子模式能量在非零动量处下降为零,等离子体波动变慢,价电子结晶成激子凝聚物。研究结果为三维固体中激子凝聚提供确信证据。

 

Bose condensation has shaped our understanding of macroscopic quantum phenomena, having been realized in superconductors, atomic gases, and liquid helium. Excitons are bosons that have been predicted to condense into either a superfluid or an insulating electronic crystal. Using the recently developed technique of momentum‐resolved electron energy‐loss spectroscopy (M-EELS), we studied electronic collective modes in the transition metal dichalcogenide semimetal 1T‐TiSe2. Near the phase-transition temperature (190 kelvin), the energy of the electronic mode fell to zero at nonzero momentum, indicating dynamical slowing of plasma fluctuations and crystallization of the valence electrons into an exciton condensate. Our study provides compelling evidence for exciton condensation in a three-dimensional solid and establishes M-EELS as a versatile technique sensitive to valence band excitations in quantum materials.

 

13 【神经】Spatiotemporal gene expression trajectories reveal developmental hierarchies of the human cortex

基因表达的时空轨迹揭示了人类大脑皮层的发育层次

Tomasz J. Nowakowski1,2,3,*,, Aparna Bhaduri1,2,*, Alex A. Pollen et.al

http://science.sciencemag.org/content/358/6368/1318

 

(导读 柳寒石)本文中作者鉴定了在发育的人类端脑中放射胶质细胞成熟和神经发生过程中的细胞类型及其基因表达的时空轨迹。其中揭示了早期放射状胶质细胞中神经发生转录因子的表达,以及mTOR信号通路在外侧胶质细胞中的富集。而放射状胶质细胞中微小的基因表达差异最终会造成成熟神经元中巨大的类型差异。因此提出了关于人类端脑的时空调控综合模型。

 

Systematic analyses of spatiotemporal gene expression trajectories during organogenesis have been challenging because diverse cell types at different stages of maturation and differentiation coexist in the emerging tissues. We identified discrete cell types as well as temporally and spatially restricted trajectories of radial glia maturation and neurogenesis in developing human telencephalon. These lineage-specific trajectories reveal the expression of neurogenic transcription factors in early radial glia and enriched activation of mammalian target of rapamycin signaling in outer radial glia. Across cortical areas, modest transcriptional differences among radial glia cascade into robust typological distinctions among maturing neurons. Together, our results support a mixed model of topographical, typological, and temporal hierarchies governing cell-type diversity in the developing human telencephalon, including distinct excitatory lineages emerging in rostral and caudal cerebral cortex.

 

14 【社科】Firearms and accidental deaths: Evidence from the aftermath of the Sandy Hook school shooting

Phillip B. Levine,Robin McKnight

枪支与意外死亡:桑迪胡克小学枪击案余波的证据

http://science.sciencemag.org/content/358/6368/1324

 

(导读 葛鹏)201212月在桑迪胡克小学发生枪击案后,枪支的曝光量大幅增加。枪支的销售额激增300万,谷歌搜索中对于购买与清理枪支的搜索量也有所上涨。研究使用死亡率统计数据检验因受枪击导致的意外死亡数的激增是否与枪支曝光量的增加同时发生。同时在枪支人均销量激增的国家中,对死亡人数是否增长更多进行了评估。研究发现桑迪胡克事件的导致了共有60人因意外枪击事件丧生。

 

Exposure to firearms increased substantially after the December 2012 shooting at Sandy Hook Elementary School in Newtown, Connecticut, where 20 children and 6 adults were killed. Gun sales spiked by 3 million, on the basis of the increase in the number of background checks for firearm purchases. Google searches for buying and cleaning guns increased. We used Vital Statistics mortality data to examine whether a spike in accidental firearm deaths occurred at the same time as the greater exposure to firearms. We also assessed whether the increase in these deaths was larger in those states where the spike in gun sales per capita was larger. We find that an additional 60 deaths overall, including 20 children, resulted from unintentional shootings in the immediate aftermath of Sandy Hook.

 

15 【生态】Paradoxical escape responses by narwhals (Monodon monoceros)

独角鲸矛盾的逃避反应 

Terrie M. Williams    et.al 

http://science.sciencemag.org/content/358/6368/1328

 

 (导读 董堃)北冰洋冰下降之前,独角鲸一直生活在远离人类相对独立的空间,且对于外界打扰非常敏感。本研究开发了一个可潜入水下的动物心电图 - 加速度计深度记录器,用于监测从大规模网络纠缠和搁浅后被释放的东格陵兰独角鲸的生理和行为反应,奇怪的是与增加的划水速度相比,逃跑的独角鲸的心率反而下降了。研究人员推测这种反常的反应应该与破坏生理稳态的恐惧反应有关。

 

Until recent declines in Arctic sea ice levels, narwhals (Monodon monoceros) have lived in relative isolation from human perturbation and sustained predation pressures. The resulting navety has made this cryptic, deep-diving cetacean highly susceptible to disturbance, although quantifiable effects have been lacking. We deployed a submersible, animal-borne electrocardiograph-accelerometer-depth recorder to monitor physiological and behavioral responses of East Greenland narwhals after release from net entanglement and stranding. Escaping narwhals displayed a paradoxical cardiovascular down-regulation (extreme bradycardia with heart rate ≤4 beats per minute) superimposed on exercise up-regulation (stroke frequency >25 strokes per minute and energetic costs three to six times the resting rate of energy expenditure) that rapidly depleted onboard oxygen stores. We attribute this unusual reaction to opposing cardiovascular signals—from diving, exercise, and neurocognitive fear responses—that challenge physiological homeostasis.

 

16 【生物】A small-molecule inhibitor of TRPC5 ion channels suppresses progressive kidney disease in animal models

TRPC5离子通道小分子抑制剂阻止动物模型中的进行性肾脏疾病

Yiming Zhou1,2,*, Philip Castonguay1    et.al

http://science.sciencemag.org/content/358/6368/1332

 

(导读 阿金)进行性肾脏疾病会引发局灶节段性肾小球硬化症(FSGS)。其发作与TRPC5离子通道活性介导的关系尚未清楚。本研究确认一种AC1903小分子,在患FSGS的大鼠转基因模型中,可阻断TRPC5离子通道活性,防止足细胞进一步丧失以及蛋白尿加重。提供一种有价值的潜在治疗方案。

 

Progressive kidney diseases are often associated with scarring of the kidney’s filtration unit, a condition called focal segmental glomerulosclerosis (FSGS). This scarring is due to loss of podocytes, cells critical for glomerular filtration, and leads to proteinuria and kidney failure. Inherited forms of FSGS are caused by Rac1-activating mutations, and Rac1 induces TRPC5 ion channel activity and cytoskeletal remodeling in podocytes. Whether TRPC5 activity mediates FSGS onset and progression is unknown. We identified a small molecule, AC1903, that specifically blocks TRPC5 channel activity in glomeruli of proteinuric rats. Chronic administration of AC1903 suppressed severe proteinuria and prevented podocyte loss in a transgenic rat model of FSGS. AC1903 also provided therapeutic benefit in a rat model of hypertensive proteinuric kidney disease. These data indicate that TRPC5 activity drives disease and that TRPC5 inhibitors may be valuable for the treatment of progressive kidney diseases.

 

17 【生物】Structural basis for methylphosphonate biosynthesis

甲基膦酸酯生物合成的结构基础

David A. Born, Emily C. Ulrich et.al

http://science.sciencemag.org/content/358/6368/1336

 

(导读 阿金)甲基膦酸合酶(MPnS)产生的甲基膦酸酯是甲烷在海洋上层的代谢前体。本研究解析MPnS及其相关酶羟乙膦酸双加氧酶(SaHEPD)的结构,发现二者都拥有一个相同的结构模块,并通过两种酶间的突变转换确认了甲基膦酸酯合成的关键要素。同时使用序列标记,确认海洋中普遍存在富含MPnS微生物,可证明甲基膦酸盐是上层有氧海洋中的甲烷来源。

 

Methylphosphonate synthase (MPnS) produces methylphosphonate, a metabolic precursor to methane in the upper ocean. Here, we determine a 2.35-angstrom resolution structure of MPnS and discover that it has an unusual 2-histidine-1-glutamine iron-coordinating triad. We further solve the structure of a related enzyme, hydroxyethylphosphonate dioxygenase from Streptomyces albus (SaHEPD), and find that it displays the same motif. SaHEPD can be converted into an MPnS by mutation of glutamine-adjacent residues, identifying the molecular requirements for methylphosphonate synthesis. Using these sequence markers, we find numerous putative MPnSs in marine microbiomes and confirm that MPnS is present in the abundant Pelagibacter ubique. The ubiquity of MPnS-containing microbes supports the proposal that methylphosphonate is a source of methane in the upper, aerobic ocean, where phosphorus-starved microbes catabolize methylphosphonate for its phosphorus.