CHARACTERIZATION AND ISOLATION OF PEPTIDE METABOLITES OF AN ANTIFUNGAL BACTERIAL ISOLATE IDENTIFIED AS BACILLUS AMYLOLIQUEFACIENS SUBSPECIES PLANTARUM STRAIN FZB42

摘要

Some bacteria produce antimicrobial chemicals in their immediate environments. These antimicrobial agents are enzymes, polypeptides or non-protein organic compounds. In this study, a bacterial isolate that produces antifungal chemical(s) was isolated from an over incubated nutrient agar plate that was exposed to air. The bacterium is aerobic, Gram positive bacilli; capsule and endospore producing. It ferments glucose and sucrose but not lactose, galactose, mannitol and sorbitol; it is citrate, indole, methyl red and Voges Prauskauer negative. Using agar gel diffusion technique, the cell-free culture supernatant resulting from centrifugation of a six day bacterial culture showed antifungal activity against filamentous fungi but not yeasts. Heating the cell-free supernatant in 90 ?C water bath and digestion with different proteases had no negative impact on the antifungal activity. A segment of 16S rRNA gene of the bacterial isolate was amplified. The nucleotide sequence of the amplicon was used to identify the bacterium as being very similar to Bacillus amyloliquefaciens subsp. plantarum strain FZB42. Five bacterial peptides were isolated and identified from cell free supernatant of the bacterial culture using a suite of techniques, including flash chromatography, HPLC, NMR and mass spectrometry. One of the five peptides has been previously reported in literature to possess antifungal activity.