Microbial diversity associated with ascidians: a review of research methods and application

Abstract

This paper reviews research in microbial diversity associated with ascidians (commonly known as sea squirts). The application of culture-dependent and culture-independent techniques is introduced in detail and these methods are analyzed for their advantages and limitations. Because of the limitations of available media and cultivation conditions, culture-dependent methods can only reveal a limited portion of the microorganisms in ascidians. However, the acquisition of typical microbial community members in culture remains a valuable resource for exploring their bioactive potential and relationships with the ascidian hosts. The application of metagenomic library methods has greatly accelerated ascidian metabolites studies. The next-generation sequencing techniques have led to the acquisition of an unprecedented quantity of ascidian microorganism data, providing the most comprehensive information about ascidian microbial diversity. Ascidians provide unique ecological niches that harbor an unexpected diversity of microorganisms different from planktonic bacteria in the local seawater. Microbial communities associated with ascidians tend to be species-specific and tissue-specific. Different tissue of the same ascidian may be associated with different microbial communities.