(290g) The Biology and Biotechnology of Plant-Microbe Interfaces

Plants have the incredible ability to transform atmospheric CO₂ into a wide array of compounds, from primary and secondary metabolites to complex biopolymers (e.g., cellulose, lignin, starch), all of which support and shape life on our planet. Plant-microbe interactions affect the development, health, and productivity of living plants, while another set of plant-microbe interactions affect the cycling of carbon from dead plant biomass back to the environment. Here, I will discuss two projects that demonstrate the use of systems biology and genetic engineering of non-model bacteria to understand and manipulate these interactions at plant-microbe interfaces. In the first project, the lignocellulosic biomass degradation ability of extremely thermophilic Caldicellulosiruptor species was dissected through in vitro and in vivo characterization of large multi-domain glycoside hydrolase enzymes produced by these species. Proof-of-concept engineered strains with altered biomass degradation ability or metabolic flux to fuel molecules will be presented. In the second project, interactions within the Arabidopsis root microbiome were identified that maintain hormone homeostasis and promote stereotypic root development in diverse bacterial communities. This was traced to a novel auxin hormone degradation locus conserved in Variovorax species, ubiquitous members of plant microbiomes. The genes essential to this degradation phenotype, their regulation through a MarR-family transcriptional regulator, and transfer of this pathway to a related bacterial genus will be discussed. These studies highlight a broad array of biological and biomolecular engineering techniques aimed at pinpointing bacterial genes and understanding their specialized biochemical functions at plant-microbe interfaces, with the ultimate goal of engineering these pathways and strains for applications in the bio-agriculture, bio-fuel, and bio-chemical industries.