Bacterial and Geochemical Composition of Thrombolites from Lake Sarmiento, Torres del Paine National Park of Chilean Patagonia

Abstract

Microbialites are organo-sedimentary structures formed as minerals precipitate due to the metabolic activity of microorganisms. They can be differentiated by their internal mesostructure into stromatolites and thrombolites. Lake Sarmiento, located in the Patagonia region of southern Chile, is a sub-saline alkaline lake in which living submerged and sub-fossil thrombolites are present. A submerged thrombolite was collected and one of the fragments was deposited in an experimental aquarium for 1.5 years, in order to examine possible changes to its biological and chemical composition. The bacterial biodiversity was examined using Illumina sequencing of PCR-amplified 16S V4 rRNA genes from total extracted DNA. The chemical structure was studied using XRD and bench chemical methods. The results show that in the living submerged and aquarium thrombolite samples, the Proteobacteria, Verrucomicrobia, Planctomycetes and Bacteroidetes phyla dominated the bacterial communities, which were similar at the upper taxonomic level. However, differences between the samples were detected at deeper classification levels (class, genus). Interestingly, no changes in the carbonate composition of the thrombolites were observed after culturing during 1.5 years. This study is the first to provide new insights into the bacterial community composition of thrombolites from this site. The thrombolites from Lake Sarmiento are active and contain a unique bacterial community composition. Further studies, including greater sampling and greater variety of experimental conditions in vitro (aquarium) will be helpful to create a global understanding of the microbial composition and formation of the thrombolites from Lake Sarmiento.

Keywords:

• Bacterial community
• hypersaline lakes
• thrombolites
• 16S rRNA

Acknowledgements

We thank all the members from the Laboratorio de Biotecnología, Departamento de Bioquímica y Biología Molecular from the Universidad de Chile for their interesting discussions. We also thank CONAF for giving us the sampling permissions and Mr. Andrés Ibañez, from the Laboratorio de Cristalografía, Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile for his help in the XRD analyses. We are grateful to two anonymous reviewers for very useful suggestions that substantially improved the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by FONDEF [CA13I10019 and IT16M10002] (CONICYT), Chile.