title: The biosurfactant viscosin produced by Pseudomonas fluorescens SBW25 aids spreading motility and plant growth promotion.
abstract: Food security depends on enhancing production and reducing loss to pests and pathogens. A promising alternative to agrochemicals is the use of plant growth-promoting rhizobacteria (PGPR), which are commonly associated with many, if not all, plant species. However, exploiting the benefits of PGPRs requires knowledge of bacterial function and an in-depth understanding of plant-bacteria associations. Motility is important for colonization efficiency and microbial fitness in the plant environment, but the mechanisms employed by bacteria on and around plants are not well understood. We describe and investigate an atypical mode of motility in Pseudomonas fluorescens SBW25 that was revealed only after flagellum production was eliminated by deletion of the master regulator fleQ. Our results suggest that this 'spidery spreading' is a type of surface motility. Transposon mutagenesis of SBW25ΔfleQ (SBW25Q) produced mutants, defective in viscosin production, and surface spreading was also abolished. Genetic analysis indicated growth-dependency, production of viscosin, and several potential regulatory and secretory systems involved in the spidery spreading phenotype. Moreover, viscosin both increases efficiency of surface spreading over the plant root and protects germinating seedlings in soil infected with the plant pathogen Pythium. Thus, viscosin could be a useful target for biotechnological development of plant growth promotion agents.
authors.affiliation: School of Biological Sciences, University of Reading, Reading, RG6 6AJ, UK.
authors.forename: Abdullah S
authors.initials: AS
authors.lastname: Alsohim
authors.forename: Tiffany B
authors.initials: TB
authors.lastname: Taylor
authors.forename: Glyn A
authors.initials: GA
authors.lastname: Barrett
authors.forename: Jenna
authors.initials: J
authors.lastname: Gallie
authors.forename: Xue-Xian
authors.initials: XX
authors.lastname: Zhang
authors.forename: Astrid E
authors.initials: AE
authors.lastname: Altamirano-Junqueira
authors.forename: Louise J
authors.initials: LJ
authors.lastname: Johnson
authors.forename: Paul B
authors.initials: PB
authors.lastname: Rainey
authors.forename: Robert W
authors.initials: RW
authors.lastname: Jackson
mesh_terms: D000898:Antibiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D027461:Beta vulgaris / Q000254:growth & development / Q000382:microbiology; D004251:DNA Transposable Elements; D005407:Flagella / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D009068:Movement; D010456:Peptides, Cyclic / Q000096:biosynthesis* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000096:biosynthesis* / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology*; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism*; D011775:Pythium / Q000187:drug effects / Q000254:growth & development / Q000472:pathogenicity; D036226:Seedlings / Q000254:growth & development / Q000382:microbiology; D013559:Symbiosis; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D010456:Peptides, Cyclic; D010937:Plant Growth Regulators; D015534:Trans-Activators; C062796:viscosin