Diversity and ecology of thraustochytrid protists in the marine environment

Abstract

Thraustochytrids are heterotrophic estuarine/marine protists belonging to the class Labyrinthulomycetes within the stramenopile lineage. Thraustochytrid protists have been a neglected agent of the microbial food chain; however, they occur in detectable amounts in seawater, sediment, and algal and animal tissues. They have the ability to degrade a wide variety of organic substrates, including refractory substrates, by means of extracellular enzymes. Their wide distribution and degradation capability exhibit their ecological significance as decomposers. In particular, thraustochytrids may grow on terrestrial refractory matter in riverine input, and play a role in enhancing carbon cycling in estuarine and coastal areas. Additionally, they produce high amounts of Long-Chain polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA), which are essential fatty acids for marine animals. Furthermore, some members are known to be pathogens of marine mollusks. These distinctive characteristics mean that thraustochytrid protists play a number of important roles in marine environments.