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.