Phylogenetic analysis of endophytic bacterial isolates from leaves of the medicinal plant Trichilia elegans A. Juss. (Meliaceae)

Various organisms such as fungi and bacteria can live inside plants, inhabiting the aerial parts (primarily the leaves) without causing damage. These microorganisms, called endophytes, produce an extensive variety of compounds that can be useful for medical and agronomic purposes. Trichilia elegans A. Juss., belonging to the Meliaceae family, shows wide dispersion in South America, and phytochemical analyses from these plants and endophyte isolates have shown biological activity. Accordingly, the aim of this study was to verify the diversity of bacterial endophytes from T. elegans using partial sequencing of 16S rRNA, followed by phylogenetic analysis. Isolation was performed by cutting the leaves, after disinfection with 5% sodium hypochlorite (NaOCl), in 1-2-mm² fragments, which were equally placed on dishes containing TSA and fungicide BENLATE at 75 μg/mL. All dishes were incubated at 28°C in the biochemical oxygen demand system for 5 days and periodically checked. Afterwards, the colonization frequency (%) was determined: (number of fragments colonized by bacteria/total number of fragments) x 100. Three isolations between September 2011 and March 2012 were performed; the growth frequency ranged between 1.6 and 13.6%. Following sequencing of 16S rRNA and phylogenetic analysis, the genera identified were: Staphylococcus, Bacillus, Microbacterium, Pseudomonas, and Pantoea. These results will provide important knowledge on the diversity of endophytic bacteria inhabiting medicinal plants, and a better understanding of the microbiome of T. elegans would reinforce the necessity of endophyte studies with a focus on their future applications in biotechnological areas of agriculture, medicine, and the environment.