Symbioses of Cyanobacteria in Marine Environments: Ecological Insights and Biotechnological Perspectives.

Antonia Chiarore,Valerio Mazzella,Donatella De Pascale,Christian Galasso,Emanuele Somma,Gennaro Riccio,Mirko Mutalipassi,Valerio Zupo

doi:10.3390/md19040227

Abstract

Cyanobacteria are a diversified phylum of nitrogen-fixing, photo-oxygenic bacteria able to colonize a wide array of environments. In addition to their fundamental role as diazotrophs, they produce a plethora of bioactive molecules, often as secondary metabolites, exhibiting various biological and ecological functions to be further investigated. Among all the identified species, cyanobacteria are capable to embrace symbiotic relationships in marine environments with organisms such as protozoans, macroalgae, seagrasses, and sponges, up to ascidians and other invertebrates. These symbioses have been demonstrated to dramatically change the cyanobacteria physiology, inducing the production of usually unexpressed bioactive molecules. Indeed, metabolic changes in cyanobacteria engaged in a symbiotic relationship are triggered by an exchange of infochemicals and activate silenced pathways. Drug discovery studies demonstrated that those molecules have interesting biotechnological perspectives. In this review, we explore the cyanobacterial symbioses in marine environments, considering them not only as diazotrophs but taking into consideration exchanges of infochemicals as well and emphasizing both the chemical ecology of relationship and the candidate biotechnological value for pharmaceutical and nutraceutical applications.

Highlights

Cyanobacteria and Their Symbiotic AssociationsCyanobacteria are a wide and diversified phylum of bacteria capable of photosynthesis.They are found in symbiosis with a remarkable variety of hosts, in a wide range of environments (Figure 1)
Cyanobacterial symbionts are active producers of secondary metabolites and toxins [21], able to synthesize a large array of bioactive molecules, such as photoprotective and anti-grazing compounds [4,22]
Several investigations demonstrated an influence of host organisms on the production of cyanobiont secondary metabolites, as in the case of the symbiotic interaction of Nostoc cyanobacteria with the terrestrial plant of Gunnera and Blasia genera [23]

Summary

Introduction

Cyanobacteria are a wide and diversified phylum of bacteria capable of photosynthesis. Several investigations demonstrated an influence of host organisms on the production of cyanobiont secondary metabolites, as in the case of the symbiotic interaction of Nostoc cyanobacteria with the terrestrial plant of Gunnera and Blasia genera [23]. Changes in the metabolic profiles have probably a clear role in the formation of cyanobacterial motile filaments (hormogonia) and, most probably, they affect the infection process and the symbiotic relationship itself [24] This suggests that cyanobacterial secondary metabolites may play a key role in host–cyanobacterium communications. There are lines of evidence that cyanobionts produce novel compounds of interest to pharmaceutical research [25,26], exhibiting cytotoxic and antibacterial activities Some of these molecules are produced by cyanobacteria only in a symbiotic relationship, as in the case of polyketide nosperin (Figure 2) [27].

Structure

Protists

Macroalgae and Seagrasses

Sponges

Cnidarians

Ascidians and Other Tunicates

Metabolic Interactions Involved in Symbiosis of Cyanobacteria

Bioprospecting of Cyanobacteria Symbioses

Findings

Conclusions