Investigating the role of exudates in recruiting Streptomyces bacteria to the Arabidopsis thaliana root microbiome

Sarah F. Worsley, Michael C. Macey, Jake T. Newitt, Elaine Patrick, Douglas W. Yu, Barrie Wilkinson, J. Colin Murrell and Matthew I Hutchings

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Mar 04, 2019
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Received Date: 15th February 19

Arabidopsis thaliana has a diverse but consistent root microbiome, recruited in part by the release of fixed carbon in root exudates. Here we focussed on the recruitment of Streptomyces bacteria, which are well established plant-growth-promoting rhizobacteria and which have been proposed to be recruited to A. thaliana roots by the release of salicylic acid. We generated high quality genome sequences for eight Streptomycesendophyte strains and showed that although some strains do enhance plant growth, they are not attracted to, and do not feed on, salicyclic acid. We used 13CO2DNA-stable isotope probing to determine which bacteria are fed by the plants in the rhizo- and endosphere and found that streptomycetes did not feed on root exudates in vivo, despite the fact that they can use exudate as sole carbon and nitrogen sourcesin vitro. We confirmed increased root colonisation by streptomycetes in plants that constitutively produce salicylic acid, but these plants exhibited a pleiotropic phenotype of early senescence and weak growth. We propose that streptomycetes are attracted to the rhizosphere by root exudates but can be outcompeted for this food source by more abundant proteobacteria and most likely feed off unlabelled complex organic matter.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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