Roles and recruitment of Streptomyces species in the wheat root microbiome.

Newitt, Jake (2020) Roles and recruitment of Streptomyces species in the wheat root microbiome. Doctoral thesis, University of East Anglia.

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Abstract

The demand for staple food crops is rising alongside the world’s population and matching supply to demand is one of the greatest challenges facing global food security. A key strategy is to better understand and exploit microorganisms that associate with plant roots, thus improving growth and reducing the incidence of disease. Streptomyces is a genus of bacteria that are consistently found in soil and are well known for their diverse and specialised metabolism. A growing body of literature documents their association with higher Eukaryotes, including plants. Their ability to improve plant growth by alleviating stress and reducing disease has been documented, but factors determining their recruitment are enigmatic.

Many Streptomyces spp. produce specialised metabolites that kill the wheat take-all fungus, G. tritici, but it is not known how widespread this trait is. This study shows that at least 17 out of 54 streptomycetes (31%) isolated from wheat roots can inhibit the growth of wheat take-all fungus. Isolates from the Paragon variety showed greater antifungal activity which may implicate host genotype with functional variation of the root microbiome. The genomes of two Streptomyces strains with exceptionally potent antifungal activity were sequenced and putative antifungal gene cluters were identified. Root exudates are hypothesised to play a key role in the recruitment of beneficial microbes and 13CO2 DNA stable isotope probing (SIP) experiment revealed that many of the rhizosphere enriched bacterial taxa utilised wheat root exudates. Surprisingly, Streptomycetaceae were not metabolising root exudates in the rhizosphere but the data suggested that are feeding on plant metabolites in the endosphere, where they have less competition. Whole bacterial community analysis showed their abundance was significantly enriched in the endosphere compartment. Nitric oxide (NO) was implicated for the first time in the recruitment of Steptomyces bacteria to the plant rhizosphere using S. coelicolor as a model. Mutant strains with deletions in genes coding for NO detoxification colonised the rhizosphere better than the control, while bulk soil was survival was unaffected, suggesting NO enhances root colonisation by these bacteria.

Overall, this research gives new insight into the ecological roles of Streptomyces spp. and supports the hypothesis that they are useful plant growth promoting bacteria that could be exploited as plant probiotics.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	16 Sep 2021 13:39
Last Modified:	16 Sep 2021 13:46
URI:	https://ueaeprints.uea.ac.uk/id/eprint/81445
DOI:

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