编译|李言

Nature,19 September 2024, Volume 633 Issue 8030

《自然》，2024年9月19日，第633卷，8030期

化学Chemistry

Growth of complete ammonia oxidizers on guanidine

完全氨氧化剂在胍上的生长

▲ 作者：Marton Palatinszky, Craig W. Herbold et al.

▲链接：

https://www.nature.com/articles/s41586-024-07832-z

▲摘要：

在此，我们证明了完全氨氧化剂硝化螺旋菌和大多数其他comammox微生物可以以胍为唯一的能量、还原剂和氮源生长。蛋白质组学、酶动力学和晶体结构的研究表明，它是一种真正的胍酶。含comammox的农业土壤和污水处理厂微生物组的培养实验表明，胍是环境中硝化作用的底物。胍作为comammox生长底物的鉴定显示了这些全球重要硝化菌的出乎意料的生态位，并为它们的分离提供了机会。

▲ Abstract：

Here we show that the complete ammonia oxidizer (comammox) Nitrospira inopinata and probably most other comammox microorganisms can grow on guanidine as the sole source of energy, reductant and nitrogen. Proteomics, enzyme kinetics and the crystal structure of a N. inopinata guanidinase homologue demonstrated that it is a bona fide guanidinase. Incubation experiments with comammox-containing agricultural soil and wastewater treatment plant microbiomes suggested that guanidine serves as substrate for nitrification in the environment. The identification of guanidine as a growth substrate for comammox shows an unexpected niche of these globally important nitrifiers and offers opportunities for their isolation.

物理学Physics

Dynamic transition and Galilean relativity of current-driven skyrmions

电流驱动斯格明子的动态跃迁和伽利略相对性

▲ 作者：Max T. Birch, Ilya Belopolski et al.

▲链接：

https://www.nature.com/articles/s41586-024-07859-2

▲摘要：

在这里，我们报告了Gd₂PdSi₃中由其显著的拓扑霍尔效应（THE）所促进的斯格明子晶格（SkL）运动引发的新兴电动力学现象。随着电流激励的增加，我们观察到SkL运动从钉住状态到蠕变状态，最后到流动状态的动态转变，其中THE完全被抑制。

我们认为，即使在如目前的化合物的复杂多带系统中，也可以在流动状态中恢复完全抵消所需要的伽利略相对性。此外，我们观察到的电压足够大，可以实时测量SkL的速度—电流曲线。该曲线显示SkL在蠕变状态下的惯性运动，表现为斯格明子速度的电流滞后现象。

▲ Abstract：

Here we report the emergent electrodynamics induced by SkL motion in Gd₂PdSi₃, facilitated by its giant THE. With increasing current excitation, we observe the dynamic transition of the SkL motion from the pinned to creep regime and finally to the flow regime, in which the THE is totally suppressed. We argue that the Galilean relativity required for the total cancellation of the THE may be generically recovered in the flow regime, even in complex multiband systems such as the present compound. Moreover, the observed THE voltages are large enough to enable real-time measurement of the SkL velocity–current profile, which shows the inertial-like motion of the SkL in the creep regime, appearing as the current hysteresis of the skyrmion velocity.

医学Medicine

Frontostriatal salience network expansion in individuals in depression

抑郁症患者的额纹状体显著网络扩展

▲ 作者：Charles J. Lynch, Immanuel G. Elbau et al.

▲链接：

https://www.nature.com/articles/s41586-024-07805-2

▲摘要：

在此，使用精确的函数映射和几个深度采样的个体样本，我们发现大多数抑郁症患者的额纹状体显著性网络在皮质中扩展了近两倍。这种效应在几个样本中是可复制的，主要是由网络边界移动引起的，在不同的个体中发生了三种不同的入侵模式。

随着时间的推移，显著性网络扩展是稳定的，不受情绪状态的影响，在青春期后期抑郁发作前的儿童中可以检测到。在1.5年的时间里，我们对患者进行了多达62次的纵向分析，发现了额纹状体回路的连通性变化，追踪了特定症状的波动，并预测了未来的快感缺乏症状。

总之，这些发现确定了一种特征样的大脑网络拓扑结构。它可能带来抑郁症的风险，以及额纹状体回路中情绪状态依赖性连接的变化，这些变化可以预测抑郁症状随时间的出现和缓解。

▲ Abstract：

Here, using precision functional mapping and several samples of deeply sampled individuals, we found that the frontostriatal salience network is expanded nearly twofold in the cortex of most individuals with depression. This effect was replicable in several samples and caused primarily by network border shifts, with three distinct modes of encroachment occurring in different individuals. Salience network expansion was stable over time, unaffected by mood state and detectable in children before the onset of depression later in adolescence. Longitudinal analyses of individuals scanned up to 62 times over 1.5 years identified connectivity changes in frontostriatal circuits that tracked fluctuations in specific symptoms and predicted future anhedonia symptoms. Together, these findings identify a trait-like brain network topology that may confer risk for depression and mood-state-dependent connectivity changes in frontostriatal circuits that predict the emergence and remission of depressive symptoms over time.

地球科学Earth Science

Decoding drivers of carbon flux attenuation in the oceanic biological pump

解码海洋生物泵中碳通量衰减的驱动因素

▲ 作者：M. Bressac, E. C. Laurenceau-Cornec et al.

▲链接：

https://www.nature.com/articles/s41586-024-07850-x

▲摘要：

在此，我们展示了C-RESPIRE的原位实验结果。C-RESPIRE是一种部署在多个中层深度的双粒子拦截器和培养箱，用于测量微生物介导的颗粒有机碳（POC）通量衰减。

我们发现，在6个不同的海洋体系中，即POC通量的30倍范围内，颗粒附着微生物的降解为通量衰减的7%—29%，这意味着浮游动物在通量衰减中发挥了更大的影响作用。微生物再矿化，标准化到POC通量，在不同的地点和深度范围20倍，在高POC通量下速率最低。

高达三倍变化的垂直趋势与低纬度地区强烈的温度梯度有关。与之相反，在中高纬度地区，温度的影响较小，而垂直趋势可能由颗粒生物化学、破碎化和微生物生态生理共同决定。马丁曲线的解构揭示了驱动微生物介导的POC通量衰减的基本机制。

▲ Abstract：

Here we present in situ experimental findings from C-RESPIRE, a dual particle interceptor and incubator deployed at multiple mesopelagic depths, measuring microbially mediated POC flux attenuation. We find that across six contrasting oceanic regimes, representing a 30-fold range in POC flux, degradation by particle-attached microbes comprised 7–29 per cent of flux attenuation, implying a more influential role for zooplankton in flux attenuation. Microbial remineralization, normalized to POC flux, ranged by 20-fold across sites and depths, with the lowest rates at high POC fluxes. Vertical trends, of up to threefold changes, were linked to strong temperature gradients at low-latitude sites. In contrast, temperature played a lesser role at mid- and high-latitude sites, where vertical trends may be set jointly by particle biochemistry, fragmentation and microbial ecophysiology. This deconstruction of the Martin curve reveals the underpinning mechanisms that drive microbially mediated POC flux attenuation across oceanic provinces.

Observation-constrained projections reveal longer-than-expected dry spells

预测显示干旱期将长于预期

▲ 作者：Irina Y. Petrova, Diego G. Miralles et al.

▲链接：

https://www.nature.com/articles/s41586-024-07887-y

▲摘要：

在此，我们表明使用新提出的紧急约束（EC）来约束模型预测，可以在全球范围内将核心干旱指标——最长年度干旱期（LAD）——预测的不确定性降低10%—26%。经EC校正后的预测结果显示，与目前预测的未来作用力情景相比，LAD的平均增幅将高出42%—44%。这些结果表明，到本世纪末，全球平均仅陆地的LAD可能比目前预计的要长10天。

利用两代气候模式，我们进一步揭示了历史LAD偏差影响预估LAD增加幅度的全球区域，并探讨了陆地—大气反馈在其中的作用。我们的研究结果揭示了一些地区的社会和生态系统可能面临比预期更高、更早的干旱风险，并指出了当前一代气候模型中存在偏差的可能机制。

▲ Abstract：

Here we show that constraining model projections with observations using a newly proposed emergent constraint (EC) reduces the uncertainty in predictions of a core drought indicator, the longest annual dry spell (LAD), by 10–26% globally. Our EC-corrected projections reveal that the increase in LAD will be 42–44% greater, on average, than ‘mid-range’ or ‘high-end’ future forcing scenarios currently indicate. These results imply that by the end of this century, the global mean land-only LAD could be 10 days longer than currently expected. Using two generations of climate models, we further uncover global regions for which historical LAD biases affect the magnitude of projected LAD increases, and we explore the role of land–atmosphere feedbacks therein. Our findings reveal regions with potentially higher- and earlier-than-expected drought risks for societies and ecosystems, and they point to possible mechanisms underlying the biases in the current generation of climate models.

A climate threshold for ocean deoxygenation during the Early Cretaceous

白垩纪早期海洋脱氧的气候阈值

▲ 作者：Kohen W. Bauer, N. Ryan McKenzie et al.

▲链接：

https://www.nature.com/articles/s41586-024-07876-1

▲摘要：

在此，我们的研究显示，在白垩纪大洋缺氧事件（OAE1a）期间海洋快速脱氧与火山二氧化碳排放和相关气候阈值的跨越有关。此后，硅酸盐风化反馈和气候恢复的缓慢步伐将再氧化的延迟事件大于1百万年。在OAE1a结束时，重新越过这个阈值并使得海洋再氧化。

然而，在OAE1a之后，地球系统保持足够的温暖，以至于轨道驱动的气候动力学导致海洋在大约10亿年的时间尺度上继续循环脱氧，并持续了1百万年。因此，我们的结果暗示了火山作用、风化作用和海洋氧含量之间的紧密耦合，这种耦合以气候阈值为特征。

▲ Abstract：

Here we show that rapid ocean deoxygenation during OAE1a is linked to volcanic CO₂emissions and the crossing of an associated climate threshold, after which the sluggish pace of the silicate-weathering feedback and climate recovery delayed reoxygenation for >1 Myr. At the end of OAE1a, recrossing this threshold allowed for ocean reoxygenation. Following OAE1a, however, the Earth system remained sufficiently warm such that orbitally forced climate dynamics led to continued cyclic ocean deoxygenation on approximately 100-kyr timescales for another 1 Myr. Our results thus imply a tight coupling between volcanism, weathering and ocean oxygen content that is characterized by a climate threshold.