Cell envelope-associated components contribute to pathogenicity towards pest insects and competitiveness of root-colonizing pseudomonads with biocontrol activities
C. KEEL (1), P. Kupferschmied (1), M. Péchy-Tarr (2), C. Terrettaz (2), P. Flury (3), T. Smits (4), M. Maurhofer (3) (1) University of Lausanne, Switzerland; (2) University of Lausanne, Switzerland; (3) Swiss Federal Institute of Technology (ETH), Switzerland; (4) Zürich University of Applied Sciences, Switzerland

Some root-colonizing pseudomonads exhibit manifold plant-beneficial activities, including the suppression of diseases caused by pathogenic fungi and protists, the induction of local and systemic defences, and the promotion of growth and nutrition. We discovered that phylogenetically distinct members of these rhizosphere bacteria, notably Pseudomonas protegens and Pseudomonas chlororaphis, exhibit in addition potent oral and systemic insecticidal activities. They invade herbivorous larvae of several Lepidopteran and Dipteran pest insects with ease. Following oral uptake, they colonize the insect gut, breach through the intestinal epithelial barrier to gain the hemocoel, where they proliferate and ultimately kill the insect. An insecticidal protein, which we termed the Fit toxin, functions as a major, but not exclusive, determinant of insect pathogenicity in these pseudomonads. Comparative genomics and targeted mutational analyses allowed us to identify additional pathogenicity factors, among them extracellular products with toxic and lytic activities and in particular cell envelope-associated components, notably lipopolysaccharide O-antigen, exopolysaccharides and type VI secretion-associated factors. The tailored efficacious equipment may enable these bacteria to competitively colonize certain insects while avoiding their immune response and to switch from a plant- to an insect-adapted lifestyle when opportune.

Abstract Number: C16-5
Session Type: Concurrent