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Multiple antibiotics produced by Pseudomonas fluorescens HV37a and their differential regulation by glucose
Abstract:
Pseudomonas fluorescens HV37a inhibited growth of the fungus Pythium ultimum on potato dextrose agar (PDA). An antibiotic activity produced under these conditions was fractionated and partially characterized. Extracts prepared from the PDA on which HV37a was grown revealed a single peak of antibiotic activity on thin-layer chromatograms. Similar extracts were prepared from mutants of HV37a. Their analysis indicated that the antibiotic observed in thin-layer chromatograms was responsible for fungal inhibition observed on PDA. The production of the PDA antibiotic required the presence of glucose, whereas two other antibiotic activities were produced only on potato agar without added glucose. Two mutants (denoted AfuIa and AfuIb) previously characterized as deficient in fungal inhibition on PDA showed altered regulation of the production of all three antibiotics in response to glucose. These mutants were also deficient in glucose dehydrogenase. Mutants isolated as deficient in glucose dehydrogenase were also deficient in fungal inhibition and were grouped into two classes on the basis of complementation analysis with an AfuI cosmid. Glucose regulation of antibiotic biosynthesis therefore involves at least two components and requires glucose dehydrogenase.
Insights
Pseudomonas fluorescens HV37a produces an antibiotic that inhibits Pythium ultimum growth. Glucose regulation of this antibiotic biosynthesis involves glucose dehydrogenase and at least two other components.
Area of Science:
- Microbiology
- Biochemistry
- Plant Pathology
Background:
- Pseudomonas fluorescens HV37a exhibits antifungal properties against Pythium ultimum.
- Antibiotic production by P. fluorescens HV37a is influenced by growth medium composition.
Purpose of the Study:
- To characterize the antibiotic responsible for fungal inhibition.
- To investigate the role of glucose in regulating antibiotic biosynthesis.
- To elucidate the genetic components involved in glucose-mediated antibiotic production.
Main Methods:
- Fractionation and partial characterization of antibiotic activity.
- Thin-layer chromatography (TLC) analysis of extracts.
- Comparative analysis of wild-type and mutant strains of P. fluorescens HV37a.
- Complementation analysis of mutants deficient in glucose dehydrogenase.
Main Results:
- A single antibiotic peak on TLC correlated with fungal inhibition on potato dextrose agar (PDA).
- Glucose presence was required for the production of the PDA antibiotic.
- Two other antibiotic activities were produced in the absence of glucose.
- Mutants deficient in glucose dehydrogenase showed altered antibiotic production and fungal inhibition.
- Complementation analysis identified two classes of mutants involved in glucose regulation.
Conclusions:
- Glucose regulation of P. fluorescens HV37a antibiotic biosynthesis is complex, involving glucose dehydrogenase and at least two other regulatory components.
- Glucose dehydrogenase plays a critical role in the glucose-dependent regulation of antifungal antibiotic production.