Metabolic Changes of Phomopsis longicolla Fermentation and Its Effect on Antimicrobial Activity Against Xanthomonas oryzae

Genomics Division, National Academy of Agricultural Science (NAAS), Rural Development Administration (RDA), Suwon 441-857, KoreaReceived: October 10, 2012 / Revised: October 24, 2012 / Accepted: October 26, 2012Bacterial blight, an important and potentially destructivebacterial disease in rice caused by Xanthomonas oryzae pv.oryzae (Xoo), has recently developed resistance to theavailable antibiotics. In this study, mass spectrometry(MS)-based metabolite profiling and multivariate analysiswere employed to investigate the correlation between time-dependent metabolite changes and antimicrobial activitiesagainst Xoo over the course of Phomopsis longicolla S1B4fermentation. Metabolites were clearly differentiated basedon fermentation time into phase 1 (days 4-8) and phase 2(days 10-20) in the principal component analysis (PCA)plot. The multivariate statistical analysis showed that themetabolites contributing significantly for phases 1 and 2were deacetylphomoxanthone B, monodeacetylphomoxanthoneB, fusaristatin A, and dicerandrols A, B, and C asidentified by liquid chromatography-mass spectrometry(LC-MS), and dimethylglycine, isobutyric acid, pyruvicacid, ribofuranose, galactofuranose, fructose, arabinose,hexitol, myristic acid, and propylstearic acid were identifiedby gas chromatography-mass spectrometry (GC-MS)-basedmetabolite profiling. The most significantly differentsecondary metabolites, especially deacetylphomoxanthoneB, monodeacetylphomoxanthone B, and dicerandrol A, Band C, were positively correlated with antibacterialactivity against Xoo during fermentation. Key words: Antimicrobial activity, metabolite profiling,Phomopsis longicolla, principal component analysis,Xanthomonas oryzaeXanthomonas oryzae pv. oryzae (Xoo) is a major pathogenof rice causing bacterial leaf blight (BLB), which leads toserious economic losses to farmers [8, 9]. Recent reportsindicate that the Xoo has produced resistance against variouschemical substances, leading to a search of high effectivedisease preventive substance against Xoo [6]. Worldwideawareness about the usage of chemical substances againstpest and disease pushes researchers to find alternativenatural substances to control such plant microbes. Recentresearch proves that the Phomopsis longicolla fermentationproducts are found to be an effective antimicrobialcompound. In our previous study, the antimicrobial activityof Phomopsis longicolla S1B4 secondary metabolites wasexamined against Xoo [6]. Identification of a novelphomoxanthone antibiotic made through metabolite profilingof Phomopsis longicolla in another study was reported(data not presented). However, the effect of fermentationon primary and secondary metabolites changes of P.longicolla S1B4 and its antimicrobial correlation againstXoo have not yet been reported. Metabolomics is an emerging and rapidly developingscience and technology that includes a comprehensiveexperimental analysis of metabolite profiles, either astargeted compounds or global metabolites [10]. Thisapproach has been previously applied to the discovery ofnovel bioactive compounds and the optimization of thefermentation process [10, 11]. In metabolite profiling, it ispreferable to use a wide-spectrum metabolite analysistechnique that is rapid, reproducible, and stable duringsample analysis [2]. Mass spectrometry (MS) is one of thetechniques that can meet such demands. MS has beenfrequently used in earlier studies to detect and quantify themetabolome [12]. In the last few decades, a number ofchemometric tools have been applied to the interpretationand quality assessment of MS-based metabolomic data. In this study, the metabolic changes of P. longicollaS1B4 during fermentation and its antimicrobial activityagainst Xoo are reported. Principal component analysis