Identification and bioactive properties of endophytic fungi isolated from phyllodes of Acacia species

Endophytes are microorganisms that exist within the tissues of living plants. Generally the relationship between the plant and its endophytes is symbiotic whereby the endophytes colonise the internal tissues of the plant without any adverse effects on the host. In the past two decades, there has been growing interest in endophytes and their origins, their biodiversity, endophyte-host interactions, their role in ecology and the characterisation of their secondary metabolites. However, the sheer diversity of plant-endophyte relationships means that only a handful of plants, mainly grass species, have been completely studied in relation to their endophytic biology. The genus Acacia comprises over 1300 species of which nearly 1000 are found in Australia. Acacia species are used widely as food (e.g. seeds are ground into flour and the gum is edible) and the wood has been traditionally made into clubs, spears, boomerangs and shields. Various species are used as narcotics and painkillers, to treat headaches, cold and fevers, as antiseptics and bactericides and to treat skin disorders by the indigenous people of Australia. While there is some information available about the medicinal properties of Acacia, there is no information about the endophytic microorganisms of these plants. With increased need for new bioactive compounds with medical, industrial or biotechnological applications, we have investigated the bioactive properties of fungal endophytes of Acacia species. Specifically, we have isolated endophytic fungi from the phyllodes of Acacia baileyana, Acacia podalyriifolia and Acacia floribunda. These were classified as Aureobasidium, Chaetomium and Sordariomycetes through genetic analysis of ribosomal RNA genes. The bioactivity of the fungal endophytes was examined and a number of isolates exhibited antibacterial and antifungal properties. Other isolates also exhibited amylase activity and were thus able to hydrolyse starch. This study showed that fungal endophytes are readily isolated from the phyllodes of Acacia species and that these exhibit promising bioactive properties. Thus, endophytes from Australian native plants may be a useful source of novel bioactive compounds