Diversity of Endophytes in Tropical Forests

Abstract

The world of microorganisms is vast and spectacular, as they are found everywhere in nature. Endophytic microorganisms are discovered inside healthy plant tissues and resemble the normal microbiota of the animal intestinal system. Such microbes are thought to reside inter- or intracellular in almost all types of plant tissues. Endophytes are omnipresent and exist within all known plants in various ecosystems, but the geographic differences in endophyte diversity, community composition and host/tissue preference have not been well documented yet. Endophytic microorganisms can be biotrophic mutualists, benign commensals, decomposers, or latent pathogens. Studies have found that mutualistic microbes produce toxins including several classes of alkaloids that provide resistance to herbivores. In return, plants give microbes cellular or intracellular spaces as their shelter and nutrients for their growth. Endophytes that are normally unnoticed may play a significant role in plant diversity and ecological functioning. Endophyte-infected plants reduce the correlation between diversity and eco-functioning. For example, a plant harbouring endophytes often acquires more biomass than an uninfected one and contributes less productivity in that community. Tropical ecosystems are different in important ways from those of temperate regions. They are a major reservoir of plant biodiversity and play crucial roles in global climate regulation and biogeochemical cycling. However, limited information is available about the diversity of endophytic microbial communities in these forests. Earth has forest coverage of about 31% of total land. The tropics are regions of Earth found between 23.5°N and 23.5°S of the equator. The tropical rain forest biomes cover almost 12% of Earth’s ice-free land area, of which about 20% has been brought to human concern. There are still vast areas of undisturbed rain forests that draw the highest attention of endophyte researchers. Evidence indicates that changes in climatic conditions can profoundly alter the plant-microbe symbiosis, and some conflict of interest may arise there, leading into a natural competition for individual sustainability and reproduction of endophytes. In tropical countries, diseases such as malaria, tuberculosis and cholera are prevalent. As tropical forests are considered as the most diverse terrestrial ecosystem, having the largest number of endophytic microorganisms, it also can be considered as storage for a plethora of molecules with diverse bioactivity. Limiting resources of tropical rainforests always keep the selection pressure at peak. Therefore, a high opportunity exists to obtain novel molecules with added medicinal value from endophytic microorganisms of tropical rainforests. Proper strain identification by modern molecular polyphasic approach can disclose the true diversity of the endospheric ecosystem.