Taxonomic and Metabolite Diversity of Actinomycetes Associated with Three Australian Ascidians

Larissa Buedenbender,Merrick Ekins,D Kurtböke,Anthony Carroll

doi:10.3390/d9040053

Larissa Buedenbender, Merrick Ekins + Show 2 more

Open Access

https://doi.org/10.3390/d9040053

Copy DOI

Abstract

Actinomycetes are known to be the most prolific producers of biologically active metabolites. Here, we investigated the host species-specificity and the related secondary metabolites of actinomycetes that are associated with three different Australian ascidians, namely Symplegma rubra, Aplidium solidum, and Polyclinum vasculosum. Results indicated that while isolates from the genera Streptomyces and Micromonospora were highly diverse in the ascidian samples, only two culturable actinomycete Operational Taxonomic Units (OTUs) overlapped between all of the ascidians, pointing to some degree of host species-specificity of the isolates and selective acquisition of microbial associates by the host from the surrounding environment. LC-MS/MS profiling of extracts obtained from the ascidians and their actinomycete associates revealed many overlapping ions between hosts and actinomycetes, indicating that these compounds were likely to be synthesised by the microbial associates. Laboratory cultures of the actinomycetes displayed even more diverse metabolomes than those of their ascidian hosts; thus, making ascidian-associated actinomycetes an excellent target for natural product drug discovery and biotechnology.

Highlights

Ascidians are soft-bodied, sessile, filter-feeding marine invertebrates that often rely on secondary metabolites for their defence [1,2,3]
We evaluated the microbial diversity of Australian ascidians using a culture-independent approach targeting ascidian genera, whose microbiomes had not previously been studied in breadth
The samples were collected at an intertidal habitat at Hastings Point, New South Wales, Australia and based on morphological traits the specimens were taxonomically assigned to Symplegma rubra (Figure 1c), Aplidium solidum (Figure 1d), and Polyclinum vasculosum (Figure 1e)

Summary

Introduction

Ascidians (phylum: Chordata, sub-phylum: Tunicata) are soft-bodied, sessile, filter-feeding marine invertebrates that often rely on secondary metabolites for their defence [1,2,3]. These compounds often show potent biological activity and have been recognised for their pharmaceutical and biotechnological potential. Even though ascidians have immense potential for the discovery of bioactive metabolites, sustainable supply of these bioactive molecules from wild harvesting of these animals is difficult. This is because ascidians often live in large colonies of thousands of individuals, but are only a few millimetres thick. Isolation of microbial associates provides a sustainable source of supply for the development of novel pharmaceutical drug leads, as it permits fermentation-based production of natural products rather than the harvest of enormous amounts of Diversity 2017, 9, 53; doi:10.3390/d9040053 www.mdpi.com/journal/diversity

Methods

Results

Conclusion