RESUMO
Endophytic bacteria occupy the same niche of phytopathogens and may produce metabolites that induce the host plant systemic resistance and growth. Host and environmental variables often determine the endophytic community's structure and composition. In this study, we addressed whether the plant genotype, organ, and geographic location influence the structure, composition, and functionality of endophytic bacterial communities in Paullinia cupana. To characterize the communities and identify strains with potential application in agriculture, we analyzed two P. cupana genotypes cultivated in two cities of the State of Amazonas, Brazil. Endophytic bacteria were isolated from surface-disinfested root, leaf, and seed tissues through the fragmentation and maceration techniques. The colonization rate, number of bacteria, richness, diversity, and functional traits were determined. The plant growth-promoting ability of selected bacterial strains was assessed in Sorghum bicolor. We identified 95 bacterial species distributed in 29 genera and 3 phyla (Proteobacteria, Actinobacteria, and Firmicutes). The colonization rate, richness, diversity, and species composition varied across the plant organs; the last parameter also varied across the plant genotype and location. Some strains exhibited relevant plant growth-promoting traits and antagonistic traits against the main phytopathogens of P. cupana, but they were not separated by functional traits. The main bacterial strains with plant growth-promoting traits induced S. bicolor growth. Altogether, our findings open opportunities to study the application of isolated endophytic bacterial strains in the bioprospection of processes and products.
Assuntos
Actinobacteria/isolamento & purificação , Endófitos/isolamento & purificação , Firmicutes/isolamento & purificação , Paullinia/microbiologia , Proteobactérias/isolamento & purificação , Actinobacteria/classificação , Biodiversidade , Brasil , DNA Bacteriano/genética , Endófitos/metabolismo , Firmicutes/classificação , Microbiota/fisiologia , Paullinia/crescimento & desenvolvimento , Desenvolvimento Vegetal/fisiologia , Folhas de Planta/microbiologia , Raízes de Plantas/microbiologia , Proteobactérias/classificação , RNA Ribossômico 16S/genética , Sementes/microbiologiaRESUMO
Actinomycetes are known to produce numerous secondary bioactive metabolites of pharmaceutical interest. The purpose of this study was to isolate, characterize, and investigate the antibacterial, antifungal, and anticancer activities of metabolites produced by Actinobacteria isolated from the rhizosphere of Paullinia cupana. The Actinobacteria was identified as Streptomyces hygroscopicus ACTMS-9H. Based on a bioguided study, the methanolic biomass extract obtained from submerged cultivation had the most potent antibacterial, antifungal, and cytotoxic activities. This extract was partitioned with n-hexane, ethyl acetate, and 2-butanol. Elaiophylin was isolated from the methanolic biomass extract, and its molecular formula was determined (C54H88O18) based on 1H and 13C NMR, IR and MS analyses. The 2-butanol phase was fractionated into four fractions (EB1, EB2A, EB2B, and EB3M). Chemical prospecting indicated the presence of alkaloids, saponins, and reducing sugars in the methanolic extract and 2-butanol phase. The elaiophylin displayed anticancer activity in HEp-2 and HL-60 cells with an IC50 of 1 µg/mL. The EB1 fraction was selectively toxic to HL-60 cells with IC50 of 9 ng/mL. Bioautography showed that the EB1 fraction contained an alkaloid with antibacterial and antifungal activities (MIC values ≤1.9 and <3.9 µg/mL, respectively). In conclusion, the EB1 fraction and elaiophylin of S. hygroscopicus have potent antimicrobial, antifungal, and anticancer activities.