Investigating the role of nitric oxide in plant root colonisation by Streptomyces spp

Streptomyces is a genus of soil dwelling actinomycetes that play an important role in plant health through association with plant roots. They provide an array of benefits to the plant host such as infectious disease prevention and plant growth promotion. We investigate the role of nitric oxide (NO), a ubiquitous signalling molecule used by plants and bacteria alike, in root colonisation by Streptomyces coelicolor. Plating studies were conducted for Arabidopsis thaliana and Triticum aestivum. Relative colonisation was determined by comparing selective recovery of marked mutant strains, alongside a marked control. The effect of increased endogenous NO was interrogated with a deletion mutant of nsrR-hmpA – genes responsible for NO detoxification in Streptomyces. Strains were also engineered to express recombinant NO synthase genes, to investigate the impact of NO production by the bacteria. We show that S. coelicolor ΔnsrR-hmpA is significantly more competent at colonising T. aestivum rhizosphere compared to the control (P