Love and war in the rhizosphere and engineering N2-fixation into cereals

Colonisation by bacteria of the zone surrounding plant roots (rhizosphere) is crucial to plant productivity. In spite of its importance rhizosphere colonization is poorly understood but recent advances in genome sequencing and analysis makes it possible to address this complex topic in exciting new ways. Global food security depends on sustainably maximising crop yield whilst decreasing use of costly fertilizers, which cause release of the potent greenhouse gas N2O from soils. The largest input of fixed nitrogen in the biosphere comes from the biological reduction of atmospheric N2 to ammonium, mainly through Rhizobium–legume symbioses, within which bacteria reduce N2 to ammonia for supply to the host. This frees many of the world’s major crops (e.g. soybeans, alfalfa, and peas) from nitrogenous fertilizer application and transferring nodulation to non-legume crops is a long term goal almost certain to trigger a second, environmentally sustainable, green-revolution. However, only the bacterial symbiont fixes N2 so for successful transfer we must also understand how rhizobia grow in the rhizosphere of plants and colonize their roots. We have developed radically new methods to image bacteria in their interaction with roots both temporally and quantitatively using lux fusions. This allows us to genetically dissect the bacterial and plant pathways needed for attachment, colonisation and gene regulation. Using these techniques, we will identify plant and cereal specific signals to be used in the regulation of bacterial genes such as those required for N2 fixation. It opens up a new field of root biology, where we screen for new regulatory systems to control the transkingdom interaction between plants and bacteria.

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This will suit candidates with a strong background in plant science or microbiology. Applicants would benefit from an interest and strengths in plant or bacterial genetics. It would also suite candidates interested in the protein chemistry of bacterial attachment or the physics of bacterial attachment to roots.