Bioprospecting for microbial endophytes and their natural products

The need for new and useful compounds to provide assistance and relief in all aspects of the human condition is ever growing. Drug resistance in bacteria, the appearance of life-threading viruses, the recurring problems with disease in persons with organ transplants, and the tremendous increase in the incidence of fungal infections in the world's population each only underscore our inadequacy to cope with these medical problems. Added to this are enormous difficulties in raising enough food on certain areas of the Earth to support local human populations. Environmental degradation, loss of biodiversity, and spoilage of land and water also add to problems facing mankind. Endophytes, microorganisms that reside in the tissues of living plants, are relatively unstudied and potential sources of novel natural products for exploitation in medicine, agriculture, and industry. It is noteworthy that, of the nearly 300,000 plant species that exist on the earth, each individual plant is host to one or more endophytes. Only a few these plants have ever been completely studied relative to their endophytic biology. Consequently, the opportunity to find new and interesting endophytic microorganisms among myriads of plants in different settings and ecosystems is great. The intent of this review is to provide insights into the presence of endophytes, in nature, the products that they make, and how some of these organisms are beginning to show some potential for human use. The majority of the report discusses the rationale, methods, and examples of a plethora of endophytes isolated and studied in the authors' laboratory over the course of many years. This review, however, also includes some specific examples that illustrate the work of others in this emerging field of bioprospecting the microbes of the world's rainforests.