Operational taxonomic units (OTUs) of endophytic bacteria isolated from banana cultivars in the Amazon

Endophytic microorganisms colonize plants, inhibit the growth of pathogens (by competing for nutrients and/or space), or produce antagonistic substances. Fifty-five endophytic bacteria were isolated from the leaf tissue of the FHIA 18 banana cultivar. Genetic diversity analyses were performed using the enterobacterial repetitive intergenic consensus sequence polymerase chain reaction method and BOX molecular markers. These analyses resulted in 33 and 21 polymorphic bands, respectively. The similarity data, obtained using the Dice coefficient based on the polyphasic analysis method, ranged from 22 to 100%. This indicated a high genetic diversity among the analyzed isolates. Sixty percent similarity was utilized as the cut-off criterion for the formation of operational taxonomic units (OTUs); this resulted in the identification of 32 possible OTUs, indicating a high number of potential species.

Endophytic bacteria from banana cultivars and their antifungal activity

Endophytic microorganisms consist of fungi, bacteria, and actinomycetes that play important roles in the process of plant adaptation to the environment. Currently, the natural associations between microorganisms and plant species are being explored for a large number of biotechnological applications. In this study, 122 endophytic bacteria were isolated from 5 cultivars of Musa spp from the state of Amazonas (Brazil). Four strains were selected because they exhibited antagonistic activities against Fusarium oxysporum f. sp cubense and Colletotrichum guaranicola, with inhibitions ranging from 19 to 30% and 27 to 35%, respectively. Phylogenetic analysis of the 16S rDNA regions of these bacteria with antifungal activity showed that they are phylogenetically related to 3 different species of Bacillus - B. amyloliquefaciens, B. subtilis subsp subtilis, and B. thuringiensis.