Diversidade e atividade antimicrobiana de fungos endofíticos associados à Araucaria angustifolia (Bertol.) O., Kuntze.

Endophytic fungi are characterized by inhabiting, asymptomatically, plant tissues and establish a relationship with their hosts, usually called mutualistic. This microbial group is recognized as a valuable source of secondary metabolites with different biological activities. This study aimed to characterize the community of endophytic fungi associated with Araucaria angustifolia, the only gymnosperm endemic in Brazil, and its ability to produce metabolites with antimicrobial activity. For this study, 30 specimens of A. angustifolia were collected in Campos de Altitude of the state of Minas Gerais.The leaves and stems of the A. angustifolia were superficially sterilized and inoculated in Potato Dextrose Agar (BDA) to isolate the endophytic fungi. After the isolation procedure, 316 fungal isolates were obtained. From those, 204 obtained from the leaves of and 112 from the stems, which were grouped into 140 morphotypes, distinct by electrophoretic pattern of the PCR products amplified with primer (GTG)5 .An isolate of each morphotype was selected to sequenciate the ITS region of the rDNA gene and identified as species belonging to the genera Aspergillus, Biscogniauxia, Botryosphaeria Cladosporium, Colletotrichum, Diaphorte, Mucor, Muscodor, Neofusicoccum, Neurospora, Penicillium Pezicula, Phomopsis, Pestalotiopsis, Preussia, Trichoderma and Xylaria. The most common taxa were Pestalotiopsis sp. and Xylaria sp. In other hand, Mucor circinelloides, Neurospora tetrasperma, Phomopsis chimonanthi, Botryosphaeria sp. and Biscogniauxia sp. were identified as minority taxons within the community. The community of endophytic fungi of A. angustifolia presented high values of diversity (Fisher-ɑ = 24.01), richness (Margalef's = 8.42) and dominance (Simpson's = 0.9). Moreover, the rarefaction species curve (Mao Tao), which did not reach an asymptote, suggesting that the sample size could not cover the entire range of the community associated with endophytes A. angustifolia. All isolates were cultured and their extracts, which were evaluated against the target micro-organisms Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, C. krusei and Cladosporium sphaerospermum. Twenty-five extracts were active against at least one of the target micro-organisms, from these, 21 showed selective antifungal activity and 4 of wide spectrum. Among the plant extracts obtained from leaves and stems fragments, 24 showed antibacterial activity against E. coli and 1 extract (obtained from stems fragments) showed antifungal activity against C. sphaerospermum. The extract of the fungus Pezicula eucrita displayed minimal inhibitory concentration (MIC) values of 62.5 mg/ml against C. albicans. The results of this study show that A. angustifolia, the only gymnosperm endemic to Brazil, is a promising source of diversity of tropical fungi. Furthermore, some species within the endophytic community showed the potential to produce bioactive metabolites and can be considered source of prototype molecules for drugs with antimicrobial activity.