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Pseudomonas protegens strain Pf-5 is a soil bacterium that was first described for its capacity to suppress plant diseases and has since been shown to be lethal to certain insects. Among these is the common fruit fly Drosophila melanogaster, a well-established model organism for studies evaluating the molecular and cellular basis of the immune response to bacterial challenge. Pf-5 produces the insect toxin FitD, but a ΔfitD mutant of Pf-5 retained full toxicity against D. melanogaster in a noninvasive feeding assay, indicating that FitD is not a major determinant of Pf-5's oral toxicity against this insect. Pf-5 also produces a broad spectrum of exoenzymes and natural products with antibiotic activity, whereas a mutant with a deletion in the global regulatory gene gacA produces none of these exoproducts and also lacks toxicity to D. melanogaster. In this study, we made use of a panel of Pf-5 mutants having single or multiple mutations in the biosynthetic gene clusters for seven natural products and two exoenzymes that are produced by the bacterium under the control of gacA. Our results demonstrate that the production of rhizoxin analogs, orfamide A, and chitinase are required for full oral toxicity of Pf-5 against D. melanogaster, with rhizoxins being the primary determinant., (© 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.)

Many obligate symbiotic fungi are difficult to maintain in culture, and there is a growing need for alternative approaches to obtaining tissue and subsequent genomic assemblies from such species. In this study, the genome of Elaphomyces granulatus was sequenced from sporocarp tissue. The genome assembly remains on many contigs, but gene space is estimated to be mostly complete. Phylogenetic analyses revealed that the Elaphomyces lineage is most closely related to Talaromyces and Trichocomaceae s.s. The genome of E. granulatus is reduced in carbohydrate-active enzymes, despite a large expansion in genome size, both of which are consistent with what is seen in Tuber melanosporum, the other sequenced ectomycorrhizal ascomycete. A large number of transposable elements are predicted in the E. granulatus genome, especially Gypsy-like long terminal repeats, and there has also been an expansion in helicases. The metagenome is a complex community dominated by bacteria in Bradyrhizobiaceae, and there is evidence to suggest that the community may be reduced in functional capacity as estimated by KEGG pathways. Through the sequencing of sporocarp tissue, this study has provided insights into Elaphomyces phylogenetics, genomics, metagenomics and the evolution of the ectomycorrhizal association., (© 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.)