Exploring the complexity of macroalgal-bacterial interactions through interkingdom signalling system

Abstract

Macroalgae belong to a diverse group of photosynthetic organisms that play an essential role in marine ecosystems. These ecosystem engineers contribute significantly to global primary production and are the major habitat formers on rocky shores in temperate waters, providing food and shelter for marine life. Macroalgae harbour a rich diversity of associated microorganisms with varied functions related to host performance and defence. In particular, epiphytic bacterial communities have been reported as essential for normal morphological development of the algal host. Moreover, bacteria with antifouling properties are thought to protect chemically undefended macroalgae from detrimental, secondary colonization by other microscopic and macroscopic epibiota. This tight relationship suggests that macroalgae and epiphytic bacteria interact as an integrated functional entity or “holobiont”. Many of these interactions are controlled via chemical signalling systems in a type of interkingdom communication. Indeed recent studies have demonstrated that chemical signalling molecules from bacteria regulate important functions in green algae such as reproduction and host defence.