Biodiversity of endophytic microorganisms and their biotechnological potential

Abstract

Endophytic bacteria and fungi are defined as organisms that live in association with plants for most if not all of their life cycles. They live withim the intercellular spaces of plants, where they live off apoplastic nutrients. Some fungi and bacteria can be isolated from a great variety of host plant families while growing under different ecological and geographical conditions. Other endophytes are apparently restricted to host species that occur within a particular plant family. Endophytic fungi and bacteria may confer benefits to the plant, and the benefits may be reciprocal, resulting in an enhanced symbiotic system for specific plant characteristics. Therefore, the use of endophytic bacteria and fungi opens up new areas of biothechnological exploitations, which drive the necessity to isolate and culture these organisms. Endophytes are used for biological control of various plant diseases, for enhanced agronomic plant characteristic such as increased drought tolerances and nitrogen efficiency, for bioherbicides, and for pharmaceutical agents. Because these microorganisms are usually obligated biotrophic parasites, their culture, especially for fungi, if ever achieved, may be difficult and slow. The biochemical versatility and diversity of endophytes represent an enormous variety of genes that are still unknown. More and more useful gene functions are being discovered, particularly for environmental remediation and industrial processes. Endophytics also provide numerous antimicrobial compounds; for instances, the fungus Pestalotiopsis microspora, and endophytic of Hymalayan yew, Taxus walkchiana produces taxol. This compound is now marketed as an anticancer drug (Strobel et aI., Microbiology, v.142, p. 435-440,1996). This project proposes to study the biological diversity of endophytic microorganisms (considering both number of species and the partition of abundance) from important plant species growing in São Paulo State, such as: maize, soybeans, citros, coffee, cassava, Brachiaria and Dicksonia (xaxim); to study the molecular diversity (molecular systematics) present within a species or genus based comparative sequencing of the rRNAs of endophytic microorganisms; to determine the chemical diversity, mainly of secondary metabolites-"antibiotics"; to assess the potential of endophytes in the biological controlof most important pathogens of the host plants (rust in coffee, Xyllela in citros, Phytophthora in cassava, damping-off in soybeans, Phythium aphanidermatum in maize). Also, it is objective of this project to study best methods of preserving representative genera and specific groups and to organize a culture collection of ali identified endophytics. Culture collections represent valuable resources of microbial germoplasm. Our objective is to make this collection available for distribution and utilization. (AU)