Thoughts and facts about antibiotics: where we are now and where we are heading.

The declining trends in microbial metabolite and natural products research and the refocusing of this research area are discussed. Renewing natural products research requires inexhaustible natural resources, as well as new genetic techniques and microbial sources, including endophytic microbes. The numbers of known bioactive metabolites are summarized according to their microbiological origin, biological activities and chemical structures. Synthetic and natural product-based libraries are also compared. Importantly, the wide range of microbial metabolite bioactivities, future trends and the importance of prioritizing natural products over synthetic compounds are emphasized.