RESUMO
Burkholderia glumae causes bacterial leaf blight in rice, and its global spread has been exacerbated by climate change. To understand the genetic diversity and virulence of B. glumae strains isolated from rice cultivars in Perú, 47 isolates were obtained from infected rice fields, all belonging to B. glumae, and confirmed by recA and toxB sequences. The BOX-PCR typing group has 38 genomic profiles, and these turn into seven variable number tandem repeats (VNTR) haplotypes. There was no correlation between clustering and geographical origin. Nineteen strains were selected for phenotypic characterization and virulence, using both the maceration level of the onion bulb proxy and inoculation of seeds of two rice cultivars. Several strains produced pigments other than toxoflavin, which correlated with onion bulb maceration. In terms of virulence at the seed level, all strains produced inhibition at the root and coleoptile level, but the severity of symptoms varied significantly between strains, revealing significant differences in pathogenicity. There is no correlation between maceration and virulence scores, probably reflecting different virulence mechanisms depending on the host infection stage. This is the first study to evaluate the VNTR diversity and virulence of Peruvian strains of B. glumae in two commercial cultivars.
Assuntos
Burkholderia , Variação Genética , Oryza , Doenças das Plantas , Oryza/microbiologia , Burkholderia/genética , Burkholderia/patogenicidade , Burkholderia/isolamento & purificação , Doenças das Plantas/microbiologia , Virulência/genética , Filogenia , Repetições MinissatélitesRESUMO
Various diseases, including bacterial panicle blight (BPB) and sheath rot, threaten rice production. It has been established that Burkholderia glumae (B. glumae) is the causative agent of the above mentioned pathologies. In the present study, antagonistic activity, growth promotion, and the metabolite profiles of two rhizobacteria, isolated in different paddy fields, were assessed against B. glumae. Strains were identified based on 16S rRNA gene sequences, and the phylogenetic analyses showed that both strains belong to the genus Enterobacter, with high similarity to the strain Enterobacter tabaci NR146667.2 (99%). The antagonistic activity was assessed with the disc diffusion method. Active fractions were isolated through a liquid/liquid extraction with ethyl acetate (EtOAc) from the fermentation media, and their antibacterial activities were evaluated following the Clinical and Laboratory Standards Institute (CLSI) guidelines. The Pikovskaya modified medium was used to test the ability of in vitro inorganic phosphorus solubilization, and BSB1 proved to be the best inorganic phosphorus solubilizer, with a solubilization index (SI) of 4.5 ± 0.2. The glass-column fractionation of the EtOAc extracted from BCB11 produced an active fraction (25.9 mg) that inhibited the growth of five B. glumae strains by 85-95%. Further, metabolomic analysis, based on GC-MS, showed 3-phenylpropanoic acid (3-PPA) to be the main compound both in this fraction (46.7%), and in the BSB1 extract (28.6%). This compound showed antibacterial activity against all five strains of B. glumae with a minimum inhibitory concentration (MIC) of 1000 mg/L towards all of them. The results showed that rice rhizosphere microorganisms are a source of compounds that inhibit B. glumae growth and are promising plant growth promoters (PGP).
Assuntos
Antibacterianos/farmacologia , Burkholderia/patogenicidade , Enterobacter/metabolismo , Oryza/microbiologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Acetatos/química , Enterobacter/classificação , Fermentação , Cromatografia Gasosa-Espectrometria de Massas , Espectroscopia de Ressonância Magnética , Metabolômica , Fenilpropionatos/química , Fosfatos/química , Filogenia , RNA Ribossômico 16S/genética , Metabolismo Secundário , Espectroscopia de Infravermelho com Transformada de Fourier , Virulência/genéticaRESUMO
Actinobacteria are the major source of bioactive secondary metabolites and are featured in the search for antimicrobial compounds. We used nuclear magnetic resonance (RMN)-metabolic profiling and multivariate data analysis (MVDA) to correlate the metabolites' production of Streptomyces sp. PNM-9 from the algae Dictyota sp. and their biological activity against the rice phytopathogenic bacteria Burkholderia spp. The compounds 2-methyl-N-(2'-phenylethyl)-butanamide (1) and 3-methyl-N-(2'-phenylethyl)-butanamide (2) were identified through MVDA and 2D NMR experiments in the organic extract of a 15-days LB media culture of Streptomyces sp. PNM-9. Compounds 1 and 2 were isolated and their structures confirmed by one- and two-dimensional NMR and mass spectrometry (MS) data. Compounds 1 and 2 were active against the rice pathogenic bacteria Burkholderia glumae (ATCC 33,617) displaying minimal inhibitory concentration (MIC) values of 2.43 mM and 1.21 mM, respectively. The metabolomics-guided approach employing NMR-metabolic profiling was useful for marine microbial bioprospecting and suggested Streptomyces sp. PNM-9 strain and its compounds as a potential control against phytopathogenic bacteria.