Molecular taxonomy and community dynamics of Actinobacteria in marine sediments off central Chile

We used amplicon sequencing of the 16S rRNA gene to characterize the diversity and assess temporal and spatial patterns of Actinobacteria operational taxonomic units (OTUs) extracted from sediments of the Humboldt Sulfuretum located off the coast of central Chile. The sediment of this zone is rich in sulfur compounds and organic material and supports a vast microbial community that experiences seasonal changes in response to contrasting oceanographic regimes. We distinguished 498 OTUs distributed among 7 orders, 47 families, and 122 genera (5 of these have been widely recognized for their biotechnological applications), and 56 species. The temporal analyses indicated that some OTUs underwent significant temporal changes in abundance, richness, and diversity that allowed samples to be grouped by sampling dates (seasons) but not by sampling depth or location. Since Actinobacteria are mostly aerobic, higher concentrations of dissolved oxygen near the bottom during the austral autumn-winter seasons result in a more benign environment for this phylum than the upwelling-favorable spring-summer seasons when waters over the shelf are oxygen-deficient. To evaluate the taxonomic diversity and inquire into the community dynamic of Actinobacteria present in the Humboldt Sulfuretum and reported as a potentially untapped source for secondary metabolites this work benefited from culture-independent (molecular) techniques.