Photorhabdus antumapuensis sp. nov., a novel symbiotic bacterial species associated with Heterorhabditis atacamensis entomopathogenic nematodes

Abstract

One motile, Gram-negative, non-spore-forming and rod-shaped symbiotic bacterium, strain UCH-936^T, was isolated from <i>Heterorhabditis atacamensis</i> nematodes. Results of biochemical, physiological, molecular and genomic analyses suggest that it represents a new species, which we propose to name <i>Photorhabdus antumapuensis</i> sp. nov. Digital DNA-DNA hybridization shows that strain UCH-936^T is more closely related to <i>Photorhabdus kleinii</i> DSM 23513^T, but shares solely 50.5 % similarity, which is below the 70% cut-off value that delimits species boundaries in bacteria. Phylogenetic reconstructions using whole-genome sequences show that strain UCH-936^T forms a unique clade, suggesting its novel and distinct taxonomic status again. Similarly, comparative genomic analyses shows that the virulence factor flagella-related gene <i>fleR</i>, the type IV pili-related gene <i>pilL</i> and the vibriobactin-related gene <i>vibE</i> are present in the genome of strain UCH-936^T but absent in the genomes of its closest relatives. Biochemically and physiologically, UCH-936^T differs also from all closely related <i>Photorhabdus</i> species. Therefore, <i>Photorhabdus antumapuensis</i> sp. nov. is proposed as a new species with the type strain UCH-936^T (CCCT 21.06^T=CCM 9188^T=CCOS 1991^T).