Production of antifungal metabolites by the antagonistic bacterial isolate Pseudomonas resinovorans B11

The production of antifungal compound(s) by an indigenous Pseudomonas resinovorans strain B11, showing antagonistic activity against Monosporascus cannonballus, the causal fungus of muskmelon Monosporascus root rot and vine decline disease was studied. The crude antibiotics were extracted from the cell-free culture filtrate of P. resinovorans B11 by solvent extraction. Analysis of the antibiotics preparation by thin layer chromatography revealed a prominent band with an R_f of 0.23 under ultraviolet light. Results of the gas chromatography–mass spectrometry analysis revealed that two compounds with retention time (RT) of 4.25 min and 10.58 min were present in the fluorescent band eluted at R_f 0.23. By comparing the mass spectra of these compounds with those found in the NIST/ Wiley database, these compounds were identified as 5-hydroxy-2-pentanone (RT: 4.25 min) and 4-hydroxy-4-methyl-2-pentanone (RT: 10.58 min) with molecular weights of 102.13 and 116.16, respectively. The compound 4-hydroxy-4-methyl-2-pentanone has been described as one of the components of antibiotics produced by other soil bacteria. However, this is the first report of production of 4-hydroxy-4-methyl-2-pentanone by P. resinovorans B11.