Direct measurement of in situ growth and growth limitation of bacterioplankton species

海洋微生物，包括细菌和古菌，占海洋生物量的70%。这种生物质如何转化对碳和许多其他元素的全球循环有很大影响。最近的研究表明，特定地点和时间的微生物群落是由代谢多样性的共存物种组成的，最丰富的微生物不一定表现出最高的代谢活性。然而，我们仍然缺乏对基本生态参数的了解，包括不同的细菌和古菌如何对全球元素循环做出贡献，它们的质量和生长速度在不同物种中的分布情况，以及这些参数在不同条件下如何变化。该项目使用了一种新技术，可以精确测量自然样品中的单细胞质量和生长速度。其目标是描述不同物种的质量和生长如何对海洋环境变化做出反应，并确定这种反应如何转化为全球碳和其他元素的循环。这些结果填补了关于环境变化如何管理微生物种群以及由此产生的与全球气候和人类与海洋相互作用相关的更广泛过程的知识空白。除了促进对科学的理解，这项工作还有助于以高度跨学科的方式对学生和博士后学者进行学术培训，并将制作播客，向更广泛的受众介绍这项工作及其进展。该项目的核心是一项名为悬浮微通道谐振器的技术，这是一种经过充分验证的基于微流体的质量传感器，可以精确测量单个细胞的质量和生长速度。重要的是，生长是通过添加生物量直接测量的，因此反映了采集海水样本时微生物的瞬时生长。这项技术正被应用于表征来自沿海环境的一系列自然样本中不同物种的质量和生长，并辅之以基因测序和元素分析，以估计对元素循环的贡献。该项目解决了以下问题：(I)不同细菌物种在不同时间尺度上在其天然海水中生长的速度有多快，以及根据测序数据，生长与相对丰度有何关系？(Ii)单个物种对碳、氮和磷周转的贡献是什么？(Iii)在特定条件下，哪些营养物质会限制细菌生长？(Iv)种群的原位增长率是否可以从它们的单细胞质量分布中推断出来？该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Marine microbes, including bacteria and archaea, account for up to 70% of biomass in the ocean. How this biomass turns over has large implications for the global cycling of carbon and many other elements. Recent efforts have shown that a microbial community at a certain location and time is composed of metabolically diverse, co-existing species and that the most abundant microbes do not necessarily display the highest metabolic activity. However, we still lack an understanding of fundamental ecological parameters including how different bacteria and archaea contribute to global element cycles, how their mass and growth rates are distributed across the diverse species and how these parameters change under varying conditions. This project uses a novel technology that enables precise measurement of single cell mass and growth rate in natural samples. The goal is to characterize how mass and growth of diverse species respond to environmental changes in the ocean and determine how this response is translated into cycling of global carbon and other elements. The results fill a knowledge gap on how environmental changes govern microbial populations and the consequential broader processes related to global climate and human interactions with the ocean. In addition to advancing the scientific understanding, this work contributes to the academic training of students and postdoctoral scholars in a highly interdisciplinary manner and will also produce podcasts describing the work and its progress to a broader audience. Central to this project is a technology called Suspended Microchannel Resonator, a well-proven microfluidics-based mass-sensor that precisely measures mass and growth rate of individual cells. Importantly, growth is directly measured as the addition of biomass and thus reflects the instantaneous growth of a microbe at the time the seawater sample was collected. This technology is being applied to characterize mass and growth of diverse species in a series of natural samples from coastal environments and complemented with gene sequencing and elemental analysis to estimate the contributions to element cycles. The project addresses the following questions: (i) How fast do different bacterial species grow in their native seawater over different timescales and how is growth related to relative abundance from sequencing data? (ii) What is the contribution of individual species to carbon, nitrogen, and phosphorous turnover? (iii) What nutrients limit bacterial growth under given conditions? (iv) Can in situ growth rates of populations be inferred from their single cell mass distributions?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.