Simple method of detection of the strains of fluorescent Pseudomonas spp. producing antibiotics, pyrrolnitrin and phloroglucinol

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Direct colony thin-layer-chromatography (TLC) was applied for the simple and rapid detection of strains producing antifungal substances. In this method, the bacterial colony was directly pasted onto the TLC plate and it was developed twice in the same direction with different solvents. For the detection of strains producing pyrrolnitrin (Pyr), a silica gel TLC plate pasted with the colonies of Pseudomonas fluorescens W8a grown on potato peptone glucose sucrose agar medium was developed firstly with methanol and secondly with a benzene-ethyl acetate mixture. When the plate was dried out and sprayed with Ehrlich's reagent, a clear red spot appeared at Rf=0.74. For 2,4-diacetylphloroglucinol (Phl), the plate pasted with colonies of P. fluorescens LRB3W1 cultured on malt extract agar medium was developed firstly with acetone and secondly with chloroform-methanol. A blue spot was detected on the plate at Rf=0.68 after spraying with Gibbs' reagent. This method was useful to detect the antibiotic-producing strains from wheat roots which were collected from fields continuously cultivated with wheat for a long period of time. This method can also be applied to select antibiotic-deficient strains among the transposon mediated mutants of P. fluorescens W8a.