Streptomyces bacteria: antibiotic production in the wheat endosphere

Increasing food production to feed a growing world population is essential for the future survival of the human race. Our proposal focuses on wheat, one of the most important crops in the world, and a genus of antimicrobial-producing bacteria called Streptomyces that are abundant inside wheat roots. Streptomyces bacteria make numerous specialised metabolites (SMs), many of which have antimicrobial activity, and they also form mutually beneficial symbioses with insects, marine invertebrates and plants, which exchange food and housing for antimicrobials, to protect themselves against disease. We are interested in exploiting Streptomyces bacteria as biological fungicides to protect wheat against disease and we are also interested in unlocking the biosynthesis of the estimated 90% of their SMs that are encoded but not produced under laboratory conditions. Their SMs already account for 50% of all known antibiotics and genome sequencing has indicated there are many more waiting to be discovered. We have shown streptomycetes are highly enriched in the endosphere of wheat variety Paragon grown in Church Farm soil (Norfolk) relative to the rhizosphere and surrounding soil. Some Streptomyces strains have beneficial effects on wheat plants, including protection against the Take-all fungus and we have also shown that the wheat root exudate molecule IAA can increase the antimicrobial activity of a Streptomyces endophyte strain. Here we will determine which root exudate molecules attract and feed streptomycetes and test whether they induce production of SMs not made under laboratory conditions. We will also genome sequence 10 streptomycetes isolated from wheat roots which inhibit the growth of the Take-all fungus and determine if the fungus or plant can activate production of their antifungal molecules and whether these strains can be used as seed coatings to protect wheat plants against fungal disease.