Phylogenetic position of Fit insect toxin producing pseudomonads

Abstract: Fit produced by Pseudomonas fluorescens CHA0 is a novel insect toxin in rootcolonizing pseudomonads, of which a homologue is described in Photorhabdus species.However, occurrence and abundance of insect pathogenicity in plant-associated pseudomonads isstill unclear. An extensive screening outside the P. fluorescens complex identified strains ofPseudomonas chlororaphis as further Fit toxin producing candidates. Sequences of five differentP. chlororaphis strains generated in this study were used to reconstruct the evolutionary historyof the Fit toxin gene and to analyse its mode of evolution. We found that P. chlororaphis isclosely associated with a small subgroup of 2,4-diacetylphloroglucinol and pyoluteorinproducingpseudomonads, both when analyzing four housekeeping genes and the nucleotidesequences for the Fit toxin gene. Additionally, we identified purifying selection to be thepredominant mode of Fit toxin evolution.