Role of interactions between soil microbes in shaping ecosystem carbon cycling

- 土壤中蕴藏着对生态系统功能至关重要的各种微生物。土壤微生物群落是土壤碳循环的重要驱动力-它们控制着最近植物碳输入的命运，并决定了同化碳的稳定性。我们的工作表明，较高的微生物生长产量，分配给生物合成的基质比例更大，增加了社区在土壤中储存碳的能力。我们还知道，土壤非生物因素，如水分水平和资源的可用性，可以影响微生物的生长产量，从而碳封存。然而，微生物群落中的生物相互作用在决定碳循环速率中的作用还没有被探索。土地利用对土壤中微生物多样性和功能有很大的影响。在土地利用强度较低的土壤中，较高的持水能力和较高的资源可利用性导致较高的微生物密度、较高的功能多样性和较高的微生物生物量。随着微生物栖息地的连通性更大，在较低强度的土壤群落中微生物相互作用的可能性比在较高强度的土地利用中更大。个体之间的生物相互作用可以从防御、对抗和竞争，到细胞信号传导、共代谢和共生。相反，在高强度土地利用下，社区内资源有限，周转率高，社区成员之间可能会产生竞争和对抗。这些相互作用如何影响群落动态和生态系统过程还没有被理解2.项目目标：该项目旨在了解不同的微生物相互作用在驱动土壤碳循环过程中的作用，使用现场评估和有针对性的实验室实验相结合。微生物密度和多样性在土地利用强度梯度上的差异将用于研究微生物物种的共存，这是微生物相互作用的指示。这些将通过实验室围隔实验进一步测试。将具有不同微生物密度和多样性3的群落接种到无微生物的模型土壤中。时间分辨网络分析的物种共现将在组装的社区，这些将被链接到C循环率，以推断生态系统的影响。进一步的实验室实验将使用不同的培养微生物组合来研究共同基质上的相互作用和有机物分解速率。研究方法和培训：将使用扩增子和鸟枪宏基因组测序来测量田间和实验土壤中微生物群落结构和功能的变化。将使用已建立的管道进行分类和功能分类。生物信息学的支持将通过主管提供给学生。13 C标记的植物有机物将在实验室实验中用作基质，以监测分解率。在现场和实验室实验中，基因组测序和同位素方法的这种组合将使学生获得一系列独特的技术技能。

- Soils harbour an immense diversity of microorganisms that are critical to ecosystem functioning. Microbial communities in soil are significant drivers of soil carbon cycling - they control the fate of recent plant carbon inputs and determine the stability of assimilated carbon. Our work has shown that higher microbial growth yield, with a greater proportion of substrate allocated to biosynthesis, increases the ability of communities to store carbon in soils1. We also know that soil abiotic factors such as moisture levels and resource availability can affect microbial growth yield and hence carbon sequestration. However, the role of biotic interactions within microbial communities in determining carbon cycling rates has not been explored.Land use has a big impact on microbial diversity and functioning in soil. In lower land use intensity soils, higher water holding capacity and greater availability of resources leads to higher microbial density, higher functional diversity and greater microbial biomass. With the greater connectivity of microbial habitats there is a greater probability of microbial interactions in less intensive soil communities than in those from higher intensity land use. Biotic interactions among individuals can range from defence, antagonism and competition, to cell signalling, co-metabolism and symbiosis. On the contrary, resource limitation and higher turnover in communities in high intensity land use may lead to competition and antagonism between community members. How these interactions influence community dynamics and ecosystem processes has not been understood2.Project aims: The project aims to understand the role of different microbial interactions in driving carbon cycling processes in soils using a combination of field assessment and targeted lab experiments. The differences in microbial density and diversity across land use intensity gradients will be used to study co-occurrence of microbial species which is an indication of microbial interactions. These will be further tested using lab mesocosm experiments. Communities with different microbial density and diversity3 will be inoculated into microbe-free model soil. Time-resolved network analysis of species co-occurrence will be performed in the assembled communities and these will be linked to C cycling rates to infer ecosystem implications. Further lab experiments will be performed which will use different combinations of cultured microbes to study interactions on common substrates and rates of organic matter decomposition.Research methods and training:Changes in microbial community structure and functions in field and experimental soils will be measured using amplicon and shotgun metagenomic sequencing. Taxonomic and functional classification will be performed using established pipelines. Bioinformatics support will be available to the student through the supervisors. 13C-labelled plant organic matter will be used as a substrate in lab experiments to monitor decomposition rates. Such a combination of genomic sequencing and isotopic approaches in field and lab experiments will allow the student gain a range of unique technical skills.