To kill or not to kill: deciphering the metabolic triggers of a facultative algicidal bacterium Ponticoccus

Diatoms account for 20% of global primary production and have great potential as a feedstock for production of high-value products and biofuel. It is thus critical to better understand factors controlling diatom growth and physiology. Antagonistic interactions between diatoms and bacteria are important in regulating diatom growth, although very few have been characterised directly. This project builds on our previous work that identified a facultative algicidal bacterium, Ponticoccus, which can kill diatoms in a species-specific manner. The algicidal lifestyle of Ponticoccus is activated only under certain growth conditions, suggesting that a metabolic switch controls pathogenicity of this bacterium. However, we currently do not understand how P. alexandrii causes diatom cell death, what mechanisms govern the switch to a pathogenic lifestyle, or how conserved such mechanisms are. This PhD will employ our new model system to i) conduct algal-bacterial co-culture experiments to determine the environmental signalling mechanisms controlling bacterial pathogenicity, ii) employ metabolomics approaches to decipher the molecular basis for algicidal activity, iii) examine 'omic datasets to assess the presence of algicidal pathways in Ponticoccus and other antagonist bacteria. This will significantly advance understanding of how environmental factors shape the nature of biotic interactions between marine microbes, and provide insights of the molecular mechanisms underlying such interactions. This could lead to the identification of novel anti-microbials for biotechnology. Additionally, this work will provide fundamental new insights of environmentally relevant algal-bacterial interactions that are likely a significant driver of ocean carbon cycling. This project will also provide training in microbiology, genomics, physiology, and metabolomic techniques, utilising diverse expertise from the UoE and MBA.