Determining the importance of lipid remodelling in the rhizosphere bacteria

Maintaining an adequate food supply for a growing population in the face of emerging global crises presents one of the great challenging of the 21st Century. Microorganisms can have both a negative and a positive impact on plant health and thus crop production. Thus, understanding how important microbial groups survive and proliferate in the plant microbiome is pivotal to future food security (Sergaki et al., 2018).

Plant roots rapidly deplete the surrounding soil of phosphate (Pi), a labile form of phosphorus. Thus, soil microorganisms that live in and around plant roots have to be able to cope with very growth limiting levels of bioavailable phosphorus. One mechanism is to reduce the quota of phospholipids present in their cell membranes. A second and third mechanism involves the production of numerous phosphorus-related enzymes and specialised transport systems. Almost all Pi-scavenging systems are localised in either the inner or outer membranes, thus membrane composition is likely to play a key role in the functionality of the Pi-scavenging enzymes.

This project aims to determine whether a reduction in the quota of phospholipids in bacterial cell membranes effects their competitive and pathogenic abilities. Reducing the quota of phospholipids in response to a shortage of Pi can occur through an active biological mechanism called Lipid remodelling. Such remodelling potentially plays a role in dictating the permeability and selectivity of the outer membrane. Hence, we hypothesise that lipid remodelling will mediate bacterial Pi-scavenging ability through altering outer membrane enzyme activity and Pi transport. We have recently discovered the central pathway responsible for bacterial lipid remodelling, involving an unusual intracellular phospholipase (PlcP) and demonstrated that lipid remodelling is a common adaptation strategy for a diverse range of bacteria (Sebastian et al., 2016). We have also shown that this PlcP-mediated pathway is present in both pathogenic and beneficial strains of plant-associated bacteria related to Pseudomonas and Flavobacterium (Lidbury et al., 2016). Combining classical molecular genetics with cutting-edge lipidomics, proteomics and state-of-the-art plant phenomics approaches, this project aims to determine the link between Pi-scavenging and lipid remodelling using Flavobacterium johnsoniae (beneficial) and Pseudomonas syringae (pathogen) as model organisms.

BBSRC Strategic Research Priority: Understanding the Rules of Life: Microbiology

Techniques that will be undertaken during the project:

- Cutting edge ‘omics tool sets and associated bioinformatics, including lipidomics, and proteomics
- Molecular genetics and targeted mutagenesis
- Analytical skills including HPLC, ion-exchange chromatography and gas chromatography
- Biochemical skills, including membrane protein isolation and purification and mass spectrometry
- Health and safety training and handling of plant pathogens
- Skills in plant growth and disease phenomics analysis (The Wolfson Centre for Disease Phenomics, Sheffield)