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Investigating methylotroph enrichment in the rhizosphere

Plants release a large amount of the carbon that they capture through photosynthesis into soil from their roots. This exudation of carbon from roots into the soil leads to enrichment of specific bacteria, which is of interest as this has been shown has been shown to impact plant growth and health. Furthermore, growing plants represent a major terrestrial source of methanol, an organic compound with a significant role in ozone formation. However, there is a large difference between the estimated and measured concentrations of methanol entering the atmosphere, and this disparity is potentially attributable to terrestrial and plant-enriched methylotrophs, and this is the main focus of this research project. The study site is the Antirrhinum wall at the John Innes Centre owned Church Farm in Bawburgh, maintained as undisturbed former grassland.

The aim of this project is to identify the active exudate utilisers and methylotrophs in the rhizospheres of pea and wheat plants, and to elucidate whether methylotrophs and methanol oxidation are enriched in this environment. A key approach being used in exploring the presence, activity and diversity of methylotrophs in the rhizosphere is Stable Isotope Probing. This involves application of 13C labelled substrate to soil and rhizosphere samples, in addition to pulsing of plants with 13CO2 to achieve 13C labelling of the plant exudates. The active bacterial and methylotrophic community will then be characterised and quantified through sequencing of phylogenetic and key functional genes from labelled (13C) DNA, in combination with qPCR. There will also be work into isolating the main methylotrophs that are identified in these environments and exploring their impact on plant growth.

Shown in this image are the containers used for the pulsing of carbon dioxide to growing plants, in order to gain 13C incorporation into the exuded carbon from plant roots