High diversity and novelty of Actinobacteria isolated from the coastal zone of the geographically remote young volcanic Easter Island, Chile
Easter Island is an isolated volcanic island in the Pacific Ocean. Despite the extended knowledge about its origin, flora, and fauna, little is known about the bacterial diversity inhabiting this territory. Due to its isolation, Easter Island can be considered as a suitable place to evaluate microbial diversity in a geographically isolated context, what could shed light on actinobacterial occurrence, distribution, and potential novelty. In the present study, we performed a comprehensive analysis of marine Actinobacteria diversity of Easter Island by studying a large number of coastal sampling sites, which were inoculated into a broad spectrum of different culture media, where most important variations in composition included carbon and nitrogen substrates, in addition to salinity. The isolates were characterized on the basis of 16S ribosomal RNA gene sequencing and phylogenetic analysis. High actinobacterial diversity was recovered with a total of 163 pure cultures of Actinobacteria representing 72 phylotypes and 20 genera, which were unevenly distributed in different locations of the island and sample sources. The phylogenetic evaluation indicated a high degree of novelty showing that 45% of the isolates might represent new taxa. The most abundant genera in the different samples were Micromonospora, Streptomyces, Salinispora, and Dietzia. Two aspects appear of primary importance in regard to the high degree of novelty and diversity of Actinobacteria found. First, the application of various culture media significantly increased the number of species and genera obtained. Second, the geographical isolation is considered to be of importance regarding the actinobacterial novelty found.
KeywordsEaster Island Actinobacteria Pacific Ocean New taxa Polynesia
We show our gratitude to the Centre for Molecular Biology at Kiel University (IKMB) for the DNA sequencing support. We also thank Tanja Rahn for technical assistance. We thank Prof. Ute Hentschel Humeida (GEOMAR Helmholtz Centre for Ocean Research Kiel) and Prof. Frank Sönnichsen (Institut für Organische Chemie at Christian-Albrechts-Universität zu Kiel) for their fruitful feedback for the present work. Finally, I.S. thanks Millaray Sierra for her support during the research.
We thank the Deutscher Akademischer Austauschdienst (DAAD) and Helmholtz association for the financial support.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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