Microbe Profile: Salinispora tropica: natural products and the evolution of a unique marine bacterium

Salinispora tropica was originally cultured from tropical marine sediments and described as the first obligate marine actinomycete genus. Soon after its discovery, it yielded the potent proteasome inhibitor salinosporamide A, a structurally novel natural product that is currently in phase III clinical trials for the treatment of cancer. If approved, it will be the first natural product derived from a cultured marine microbe to achieve clinical relevance. S. tropica produces many other biologically active natural products, including some linked to chemical defence, thus providing ecological context for their production. However, genomic analyses reveal that most natural product biosynthetic gene clusters remain orphan, suggesting that more compounds await discovery. The abundance of biosynthetic gene clusters in S. tropica supports the concept that the small molecules they encode serve important ecological functions, while their evolutionary histories suggest a potential role in promoting diversification. Better insights into the ecological functions of microbial natural products will help inform future discovery efforts.