Eat in or eat out? The role of plant communities for microbial metabolic activity.

Plant community composition has a large influence on microbial community composition [1]. Recently, we have shown that peatland plant functional groups are associated to specific microbial communities [2]. What is not understood is if plants create a selective environment select for microbial communities that specialize on plant–specific resources (i.e. exudates or plant litter). As a first step, this project will study the link between plant species composition and the microbial community. A close plant–microbe link could entail microbial specialisation (i.e. adaptation) on plant–specific resources, causing negative priming [3], ultimately increasing the robustness of the peatland carbon sink capacity. The absence of specific plant-microbe links could indicate the microbes are generalists, suggesting the plant community to not impact the carbon sink-strength. This PhD project is structured to first determine the link between plant community (functional) composition and the microbiome at a molecular level. Next, the project aims to assess the functional identity of peatland microbial communities, and will address the question as to whether the latter are functionally adapted to the local, plant–specific, conditions, irrespective of environmental context. This project will highlight how the presence or absence of specific plant-microbe linkages affects ecosystem processes, guiding peatland conservation strategies

Approach:
Taking a multidisciplinary approach – combining community ecology, molecular microbiology and molecular biochemistry – this project will provide deeper understanding on the role of plant community assembly in defining microbial community structure and function (e.g. carbon and nitrogen cycling, organic chemistry). The primary resource for this work will be a long-term plant removal experiment in the Store Mosse peatland in Southern Sweden, to study the presence/absence of specific plant-microbe links. Further, a series of lab/mesocosm experiments will allow to test if peatland microbiomes are adapted to plant exudates or if they are generalists.

The student will use molecular and microscope techniques to detail the microbial community associated to distinct plant communities, and it relation to soil properties (e.g. organic chemistry, nutrient stoichiometry). Stable isotopes (13C, 15N) will be used to elucidate mechanistic links between plants and microbes. The functionality and structure of the microbial communities will be further studied using in- and ex-situ physiological profiling techniques (e.g MicroRespTM), gas flux measurements, and food-web modeling. Controlled mesocosm, re-assembly experiments, and lab-incubation experiments (using leachates from different plant communities) will be necessary to establish if microbial communities are functionally adapted to local environments, and will later constitute the thesis chapters.

Training:
The SPITFIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the University of Southampton, Biological Sciences. Specific training will include:
– an initial literature review/meta-analysis.
– a visit to the University of Toulouse, EcoLab, to get training in microbial food–web modeling and techniques to determine microbial functional diversity.
– setting-up experiments and analyzing results in the R statistical environment.
– molecular techniques to study microbial diversity.
– measuring and analyzing plant functional traits.
– training in isotopic tracer techniques, GHG measurements, ecophysiological profiling, and enzymatic activity to study the functionality of microbial communities.

We expect the student to maintain existing collaborations with the staff of the Store Mosse National Park, and to exchange results and translate them to conservation practice.

[1] Grigulis K et al. (2012) Journal of Ecology, 101, 47–57.
[2] Robroek BJM, et al. (2015) Journal of Ecology, 103, 925–934.
[3] Kuzyakov Y, Friedel JK and Stahr K (2000) Soil Biology and Biochemistry, 32, 1485–1498.

For more information: http://noc.ac.uk/gsnocs/project/using-plant-soil-feedbacks-enhance-ecosystem-restoration