Burkholderia species in sugarcane: the relationship among antifungal production, intrinsic antimicrobial resistance, and pest biocontrol

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The Burkholderiaceae comprises a family of environmental bacteria widespread around the planet, which reside in diverse environments and in association with plants, insects, animals, and humans and also display extraordinarily high multidrug, intrinsic antibiotic resistance. Intrinsic resistance means that these bacteria can tolerate large concentrations of many different classes of antibiotics. Burkholderia are very useful microorganisms for mankind. They can serve as agents for bioremediation, plant growth promotion, and pest biocontrol, but these beneficial properties remain virtually unexploitable because of fear of infection and antibiotic resistance. Indeed, some Burkholderia species are particularly dangerous to humans and domestic animals (e.g. melioidosis and glanders) and they are singled out as bioterrorism agents, while others (e.g. B. cenocepacia and B. multivorans) cause debilitating and often transmissible lung infections in cystic fibrosis patients. Burkholderia spp. is a main bacterium of the sugarcane cultivable bacterial community in Brazil, and can control fungal and infections by producing many different antifungal compounds. Research in our laboratories show that strains with high-level antimicrobial resistance and increased bacterial virulence in a widely used insect infection model (Galleria mellonella) display higher capacity to inhibit sugarcane pathogenic fungi. These observations suggest that antimicrobial resistance and antifungal production are interrelated. We hypothesise that antimicrobial resistance and antifungal compound production are coordinated to allow Burkholderia survival in the presence of a polymicrobial flora in the plants and also to defend and complete for nutrients against other organisms in the rhizosphere. Our proposal aims to exploit this idea to find new ways to maximise the beneficial properties of Burkholderia for use in the field (e.g. antifungal production) while reducing antimicrobial resistance in the clinic. We will combine molecular microbiology, genomics, and infection models in plants and insects to assess the hypothesis that antifungal production drives antimicrobial resistance by influencing the production of molecules that enhance bacterial cell envelope impermeability resulting in increased antibiotic resistance, which in turn increases bacterial virulence. We will also exploit these findings to develop novel ways to inhibit antimicrobial resistance and enhance pest biocontrol.