Background: Soil microbes are critical in maintaining the carbon balance in terrestrial ecosystems. This balance of microbial decomposition and stabilisation of organic matter can shift under altered environmental conditions. Droughts, in particular, reduce microbial activity and affect soil carbon cycling, and are becoming more severe and frequent due to climate change, especially so in Mediterranean ecosystems. The reduction in microbial activity may occur due to a combination of cellular water stress and constraints imposed by decreased resource diffusion and transport.
Rationale: Droughts can alter microbial processes as stress tolerant microbes are selected due to their competitive advantage or as stress tolerance is acquired through evolution. However, how these ecological and evolutionary pressures impact overall community physiology in response to drought stress is not well understood. This brings uncertainty in understanding and predicting drought impact on microbial processes and consequences for soil carbon cycling.
Aims and approach: This PhD project aims to reveal the mechanisms of drought stress response in microbial populations and impacts on overall community traits and soil carbon cycling processes in Mediterranean ecosystems from California and Spain. The aim is to study the ecological (selective) and evolutionary (adaptative) processes that shape communities under long-term drought. We will use a trait-based approach to explore population-level trade-offs between stress tolerance and growth. A combination of microbial culture isolation-based and non-cultivation molecular-based population genomics will be used to study drought-tolerant microbes. Targeted lab mesocosm experiments will also be conducted to understand the response of drought- tolerant and drought-sensitive populations to water stress and the consequences on their fitness. This population-level understanding will be used to assess community shifts in response to drought and predict ecosystem functions such as organic matter decomposition and storage.
Methods and training: We will have access to multiple sites with long-term drought treatment. Research training will be available in molecular tools, bioinformatics and ecological statistics. The Centre for Genome Enabled Biology and Medicine at University of Aberdeen houses DNA sequencing platforms which will be available to the project including training. The genomes of individual populations will be obtained through genomic sequencing of culture isolates and de novo assembly of individual genomes from shotgun metagenomics data. Analytical facilities for gas and compound-specific 13C isotope analysis will be available to the student to quantify traits like growth rate and growth yield for individual isolates using stable isotope tracers. Student will be trained in using and applying these cutting-edge tools and to integrate the microbiome data with ecosystem measures. Such a combination of microbial culturing, population genomics and stable isotope tracing approaches will allow the student to gain unique technical skills across disciplines and apply them to address key challenges linked to climate change.
Candidate Background: Applicants are expected to hold (or be about to achieve) at least a 2:1 UK Honours degree (or Equivalent) in a relevant subject such as microbiology, ecology or soil science. Applicants with a 2:2 Honours degree (or Equivalent) may be considered providing they have a Distinction or Commendation at Master’s level. We are seeing an enthusiastic PhD student with interest in omics technologies. Statistics and bioinformatics experience are desirable.
More project details are available here: https://www.quadrat.ac.uk/quadrat-projects/
How to apply: https://www.quadrat.ac.uk/how-to-apply/