Proline-based modulation of 2,4-diacetylphloroglucinol and viable cell yields in cultures of Pseudomonas fluorescens wild-type and over-producing strains

• Published in: Applied microbiology and biotechnology Vol. 68; no. 5; pp. 630 - 638
• Main Authors: Slininger, P.J, Shea-Andersh, M.A
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01-09-2005; Springer Nature B.V
• Subjects: 2,4,6-trihydroxyacetophenone; 2-diacetylphloroglucinol; antibiotics; Antifungal Agents - metabolism; Bacteria; Biological and medical sciences; Biological control; biological control agents; Biotechnology; cell culture; culture media; Fundamental and applied biological sciences. Psychology; fungal antagonists; Growth media; Metabolites; microbial growth; Microbiology; nutrient availability; Pest Control, Biological - methods; Phloroglucinol - analogs & derivatives; Phloroglucinol - metabolism; proline; Proline - metabolism; Pseudomonas fluorescens; Pseudomonas fluorescens - genetics; Pseudomonas fluorescens - metabolism; Rhizosphere; Seed germination; seed treatment; Soil Microbiology; Triticum - microbiology; Triticum aestivum; Urea; wheat; Pseudomonadales; Antifungal agent; Biological control; Modulation; Microorganism culture; Proline; Bacteria; Pseudomonadaceae; Pseudomonas fluorescens; Yield; Viability
• ISSN: 1432-0614; 0175-7598; 1432-0614
• DOI: 10.1007/s00253-005-1907-4

The antifungal compound 2,4-diacetylphloroglucinol (DAPG) is produced in the rhizosphere of wheat by pseudomonad populations responsible for the natural biological control phenomenon known as “take-all decline.” Studies were conducted to elucidate the impact of DAPG and its co-product 2,4,6-trihydroxyacetophenone (THA) on the production of Pseudomonas fluorescens for biological control. Increasing DAPG from 0.1 g/l to 0.5 g/l and THA from 0.05 g/l to 0.5 g/l significantly inhibited the growth and lowered the yield of viable bacteria in liquid cultures. On further examination of these metabolites applied in seed coatings, levels of DAPG and THA exceeding 0.05 mg/g seed significantly reduced wheat germination percentages. The three-way interaction of DAPG, THA, and culture medium ingredients was significant, and greatest seed germination loss (40-50%) was observed when 0.5 mg DAPG and 0.25 mg THA were combined in a coating of 0.5 ml culture medium per gram of seed. Based on the results of Biolog GN microplate, flask, and fermentor screens of C sources, proline was found to optimize the viable cell yields of the P. fluorescens strains tested. The combination of proline with glucose and urea as C and N sources in growth media could be optimized to minimize DAPG production and maximize the vitality of P. fluorescens Q8R1-96 and Q69c-80:miniTn5:phl20 (DAPG over-producer). In production cultures, the proline supply rate offers a potentially useful means to optimize the biological control agent yield and quality.