Microrheology reveals microscale viscosity gradients in planktonic systems.
Microrheology reveals microscale viscosity gradients in planktonic systems.
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DOI：
10.1073/pnas.2011389118
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发表时间：
2021-01-05
影响因子：
11.1
通讯作者：
Humphries S
中科院分区：
文献类型：
--
作者：
Guadayol Ò;Mendonca T;Segura-Noguera M;Wright AJ;Tassieri M;Humphries S
在海洋微生物生命展开的微观尺度上，物理是由粘度主导的。黏度的增加既减缓了溶质和颗粒的被动运输，也减缓了活动微生物的游动，从而直接或间接地影响了微生物生命的各个方面。粘度不仅取决于水的物理性质，而且还随着生物活性的变化而变化，从而使微生物能够在一定程度上控制其物理环境。我们对微流变学的使用使我们能够探索浮游植物细胞和海洋聚集体周围的粘度是如何结构的，并揭示了微生物食物网功能和海洋生物地球化学循环的空间异质性水平。浮游系统中的微生物活动创造了一个动态的、异质的微尺度海景，其中包含了多种微生物群落和具有全球意义的生态相互作用。近几十年来，人们投入了巨大的努力来理解这个复杂的系统，特别是关注化学斑块的作用，而忽略了一个控制微生物生命并受生物活性影响的物理参数：粘度。在这里，我们通过使用微流变技术揭示了浮游生物系统中粘度的空间异质性，该技术允许在与微生物相关的长度尺度上测量粘度。我们展示了黏性和浮游植物周围的藻圈的空间范围。在分析的约45%的浮游植物细胞中，我们检测到黏度增加，距离细胞延伸至30 μ m，黏度高达海水的40倍。我们还展示了这些粘度梯度是如何在溶解的浮游植物细胞周围被放大的，因为它的粘性内容物泄漏了。最后，我们报告了海洋聚集体内部粘度的保守估计，微生物活动热点，比海水中高出一个数量级。由于溶解分子、颗粒和微生物的扩散系数与粘度成反比，因此粘度的微观非均质性改变了微生物及其资源的微观分布，对浮游生态系统的功能具有普遍的影响。黏度的增加影响生态相互作用和过程，如养分吸收、趋化性和颗粒相遇，这些发生在微观尺度上，但影响全球尺度上的碳和养分循环。
At the microscopic scales at which the life of marine microbes unfolds, the physics is dominated by viscosity. Increasing viscosity slows down both the passive transport of solutes and particles and the swimming of motile microorganisms, and thus directly or indirectly affects all aspects of microbial life. Viscosity depends not only on the physical properties of water, but it also varies as a consequence of biological activity, allowing microorganisms some control over their physical landscape. Our use of microrheology allows us to explore how viscosity is structured around phytoplankton cells and marine aggregates and unveils a level of spatial heterogeneity that has implications for the functioning of the microbial food web and hence of marine biogeochemical cycles. Microbial activity in planktonic systems creates a dynamic and heterogeneous microscale seascape that harbors a diverse community of microorganisms and ecological interactions of global significance. In recent decades great effort has been put into understanding this complex system, particularly focusing on the role of chemical patchiness, while overlooking a physical parameter that governs microbial life and is affected by biological activity: viscosity. Here we reveal spatial heterogeneity of viscosity in planktonic systems by using microrheological techniques that allow measurement of viscosity at length scales relevant to microorganisms. We show the viscous nature and the spatial extent of the phycosphere, the region surrounding phytoplankton. In ∼45% of the phytoplankton cells analyzed we detected increases in viscosity that extended up to 30 µm away from the cell with up to 40 times the viscosity of seawater. We also show how these gradients of viscosity can be amplified around a lysing phytoplankton cell as its viscous contents leak away. Finally, we report conservative estimates of viscosity inside marine aggregates, hotspots of microbial activity, more than an order of magnitude higher than in seawater. Since the diffusivities of dissolved molecules, particles, and microorganisms are inversely related to viscosity, microheterogeneity in viscosity alters the microscale distribution of microorganisms and their resources, with pervasive implications for the functioning of the planktonic ecosystem. Increasing viscosities impacts ecological interactions and processes, such as nutrient uptake, chemotaxis, and particle encounter, that occur at the microscale but influence carbon and nutrient cycles at a global scale.
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DOI：
10.1073/pnas.1012319108
发表时间：
2010-12-21
影响因子：
11.1
作者：
Kindler, Kolja;Khalili, Arzhang;Stocker, Roman
通讯作者：
Stocker, Roman
影响因子：
13.6
作者：
Moradi, Nasrollah;Liu, Bo;Khalili, Arzhang
通讯作者：
Khalili, Arzhang
影响因子：
2.1
作者：
MYKLESTAD, S;HOLMHANSEN, O;VOLCANI, BE
通讯作者：
VOLCANI, BE
影响因子：
56.9
作者：
Azam, F
通讯作者：
Azam, F
影响因子：
4.4
作者：
McSwain, BS;Irvine, RL;Wilderer, PA
通讯作者：
Wilderer, PA