Outlook

Abstract

The dozen years since the publication of the first survey of naturally occurring organohalogens (1) has seen an approximate doubling of these new natural compounds, from 2,448 to 4,715, with no sign of abatement. This increase parallels the revitalization of natural products research in general, and is a consequence of improved collection, isolation, and identification techniques. An awareness of ethnobotany and folk medicine leads natural products scientists to potentially biologically active organisms. Multidimensional nuclear magnetic resonance spectroscopy, and improved X-ray crystallography and high-resolution mass spectrometry methods allow for the characterization of minute quantities of compounds. Cultivation techniques like marine bioprocessing (116, 117, 2629) permit the harvesting of target marine organisms without plundering the ocean. Remote submersibles can access otherwise inaccessible ocean depths for new marine organisms, such as a new Woods Hole Oceanographic Institution vessel capable of diving to 6,500 m (2630). This will allow for the sampling of marine bacteria and other organisms on the ocean floor; for example, the iron-oxidizing bacteria living around deep-sea thermal vents (2631) and other deep-sea organisms (2632, 2633). Moreover, marine bacteria, in general, are a new field of natural products exploration with enormous possibilities for the discovery of new natural halogenated compounds (e.g., salinosporamide A (1124)) (2634–2636), especially considering that seawater contains as many as 10⁶ bacteria cm⁻³ (2634). Marine and terrestrial fungi are also a relatively untapped source of natural products. Indeed, of the 1.5 million estimated terrestrial fungal species on Earth, only 70,000 have been described, let alone examined for their chemical content (181, 186). Similarly, marine fungi and terrestrial mosses (bryophytes) are virtually unexplored for their metabolites (188). New species of sponges continue to be discovered (115, 2637), and it has been suggested that in the oceans sponges can undergo comparatively rapid evolution leading to new species with novel metabolites (2638). Furthermore, with bacterial densities as high as 10¹⁰ bacteria g⁻¹ of sponge wet weight, sponges are “microbial fermenters” (2639), and only a fraction of the 12,000 extant sponges have been studied for their chemical composition (112). The ocean crust is also an abundant repository of microbes (2640) and has been for 3.5 billion years (2641).