Collaborative Research: Do expected evolutionary trade-offs in enzyme activities manifest at the level of microbial community function?

呼吸作用是在一系列酶催化的步骤中释放化学能的过程，通常涉及有机（含碳）化合物和氧气的消耗，以及二氧化碳和水的产生。随着温度的升高，呼吸发生和二氧化碳产生的速度也会加快。由于这个原因，人们担心在全球变暖的情况下，生活在土壤中的微生物将消耗更多的土壤碳，而土壤是世界上大部分碳的储存地。如果他们这样做，他们可能会释放更多的二氧化碳到大气中，潜在地加速全球变暖。对于这种对变暖的积极反馈是否会发生，存在很大的不确定性——部分原因是生物可以产生对温度有不同敏感性的呼吸酶。该项目的目标是测试当温度升高时，土壤微生物是否会维持最初的呼吸增加，或者随着时间的推移，它们是否会以一种与产生对温度不太敏感的酶相一致的方式减少呼吸。为了量化土壤微生物，这个为期3年的项目将使用dna测序和脂肪酸分析方法。为了确定呼吸速率，将使用气体分析技术测量土壤中的二氧化碳产量。为了产生微生物暴露的不同温度，将在冬季和夏季从北极到热带的一个梯度上收集土壤，并在不同的温度下在实验室中培养。该项目的结果将非常重要，因为它们将有助于改善土壤微生物对未来气候变化的反应和反馈的预测，促进制定管理策略，以减轻全球变暖对人类和生态系统的影响。从基础科学的角度来看，它将帮助科学家确定微生物细胞内部的反应是否可以改变影响气候系统的生态系统过程。从教育和培养的角度来看，该项目将巩固美国各大学的3名助理教授之间的合作，教授们将指导本科生进行独立研究，培养下一代美国科学家。此外，博士生将通过整合微生物学和生态系统科学的跨学科研讨会进行培训。由于微生物是推动生命赖以生存的生物地球化学过程的引擎，这种整合对于帮助指导地球的可持续管理非常重要。

Respiration is the process by which chemical energy is released in a series of enzyme-catalyzed steps typically involving the consumption of organic (carbon containing) compounds and oxygen, and the production of carbon dioxide and water. The speed at which respiration occurs, and carbon dioxide is produced, increases as temperatures increase. For this reason there is concern that microorganisms living in soil, where much of the world's carbon is stored, will consume more soil carbon under global warming. If they do, they may release more carbon dioxide into the atmosphere, potentially accelerating global warming. There is substantial uncertainty as to whether this positive feedback to warming will happen - in part because living things can produce respiratory enzymes that have different temperature sensitivities. The goal of this project is to test whether soil microbes maintain initial increases in respiration when temperatures rise, or whether over time they decrease respiration in a way that is consistent with production of less temperature-sensitive enzymes. To quantify soil microbes, this 3-year project will use DNA-sequencing and fatty-acid profiling methodologies. To determine respiration rates, carbon dioxide production from soils will be measured using gas-analysis techniques. To generate differences in temperatures to which microbes are exposed, soils will be collected across a gradient from the arctic to the tropics, in winter and in summer, and incubated in the laboratory at different temperatures.Results of this project will be important because they will help improve predictions of soil microbial responses and feedbacks to future climate changes, facilitating development of management strategies to mitigate impacts of global warming on humans and ecosystems. From the perspective of basic science, it will help scientists determine whether responses inside microbial cells can alter ecosystem processes that influence the climate system. From education and training perspectives, the project solidifies collaborations between three assistant professors in schools within the U.S. The professors will train the next generation of U.S scientists by advising undergraduate students in conducting independent research. Furthermore, doctoral students will be trained through an interdisciplinary workshop integrating microbiology and ecosystem science. As microbes are the engines that drive the biogeochemical processes on which life depends, this integration is important to help guide sustainable management of the planet.