Do tree microbiomes clean up urban air pollution?

Carbon monoxide (CO) is a ubiquitous, atmospheric trace gas produced by natural processes as well as via anthropogenic combustion processes and is toxic to humans. CO-oxidizing microorganisms are crucial in atmospheric CO removal and have previously been identified as abundant members of soil microbial communities (Cordero et al. 2019, King and Weber, 2007). More recently, we discovered that CO-oxidising bacteria also inhabit tree leaves - a vast microbial habitat - by showing that leaf wash samples of two common UK tree species, hawthorn and holly, could degrade CO (Palmer et al. 2021). We identified a variety of candidate CO-oxidising bacteria using 16S rRNA-based microbial community analysis and the functional marker gene, coxL, encoding the catalytic subunit of the CO dehydrogenase. Data mining of environmental metagenomes suggests that coxL-possessing bacteria could constitute up to 25% of the phyllosphere (above-ground plants parts) microbial community. These findings imply that phyllosphere microbiota might be a significant and previously unrealised global CO sink (Palmer et al. 2021).

Building on these findings, this project aims to characterise CO-degrading bacteria in a wider context related to seasonal changes of leaf microbiota, the bark compartment of trees as potential habitat, and exposure to CO pollution.
Using various experimental and genetic approaches, you will assess the presence, composition, abundance and activity of CO-degrading bacteria associated with these habitats, test their CO degradation ability, and assess their functional potential in various settings. This will provide fundamental new insights into the distribution, prevalence, and pollution-dependent activity of CO-degrading bacteria in the phyllosphere advancing our understanding of the CO biogeochemical cycle and potentially providing a basis for informed selection of tree species that could maximise microbial ecosystem services for mitigation of air pollution in urban areas.