Mutational disruption of the biosynthesis genes coding for the antifungal metabolite 2,4-diacetylphloroglucinol does not influence the ecological fitness of Pseudomonas fluorescens F113 in the rhizosphere of sugarbeets

• Published in: Applied and Environmental Microbiology Vol. 61; no. 8; pp. 3002 - 3007
• Main Authors: Carroll, H. (University of Cork, Cork, Ireland.), Moenne-Loccoz, Y, Dowling, D.N, O'Gara, F
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.08.1995
• Subjects: Animal, plant and microbial ecology; ANTIBIOTICOS; ANTIBIOTIQUE; AUXILIAIRE DE LUTTE BIOLOGIQUE; BETA VULGARIS; Biological and medical sciences; Biology; Fundamental and applied biological sciences. Psychology; Fungi; INOCULACION; INOCULATION; METABOLITE; METABOLITOS; Microbial ecology; Microflora of plants; MUTACION; MUTANT; MUTANTES; MUTATION; ORGANISMOS PARA CONTROL BIOLOGICO; PSEUDOMONAS FLUORESCENS; Pythium ultimum; RHIZOSPHERE; RIZOSFERA; SEMENCE; SEMILLAS; SUPERVIVENCIA; SURVIE; Vegetables; Pseudomonadales; Metabolite; Vegetal microorganism relation; Biosynthesis; Pseudomonas fluorescens; Beta vulgaris var. saccharata; Sugar plant; Chenopodiaceae; Rhizosphere; Antifungal agent; Dicotyledones; Angiospermae; Bacteria; Pseudomonadaceae; Spermatophyta; Mutation; Colonization; Fitness
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.61.8.3002-3007.1995

The ability of Pseudomonas fluorescens F113 to produce the antibiotic 2,4-diacetylphloroglucinol (DAPG) is a key factor in the biocontrol of the phytopathogenic fungus Pythium ultimum by this strain. In this study, a DAPG-producing strain (rifampin-resistant mutant F113Rif) was compared with a nearly isogenic DAPG-negative biosynthesis mutant (Tn5:lacZY derivative F113G22) in terms of the ability, to colonize and persist in the rhizosphere of sugarbeets in soil microcosms during 10 plant growth-harvest cycles totaling 270 days. Both strains persisted similarly in the rhizosphere for 27 days, regardless of whether they had been inoculated singly onto seeds or coinoculated in a 1:1 ratio. In order to simulate harvest and resowing, the roots were removed from the soil and the pots were resown with uninoculated sugarbeet seeds for nine successive 27-day growth-harvest cycles. Strains F113Rif and F113G22 performed similarly with respect to colonizing the rhizosphere of sugarbeet, even after nine cycles without reinoculation. The introduced strains had a transient effect on the size of the total culturable aerobic bacterial population. The results indicate that under these experimental conditions, the inability to produce DAPG did not reduce the ecological fitness of strain F113 in the rhizosphere of sugarbeets