Genetic barcoding of dark-spored myxomycetes (Amoebozoa) – identification, evaluation and application of a sequence similarity threshold for species differentiation in NGS studies

5 years ago

Genetic barcoding of dark-spored myxomycetes (Amoebozoa) – identification, evaluation and application of a sequence similarity threshold for species differentiation in NGS studies

Martin Schnittler, Søren Johannes Sørensen, Yun Feng, Thomas Hoppe, Mathilde Borg Dahl, Yuri Novozhilov, Martin Unterseher, Asker Daniel Brejnrod

Unicellular, eukaryotic organisms (protists) play a key role in soil food webs as major predators of microorganisms. However, due to the polyphyletic nature of protists no single universal barcode can be established for this group, and the structure of many protistean communities remains unresolved. Plasmodial slime molds (Myxogastria or Myxomycetes) stand out among protists by their formation of fruit bodies, which allow for a morphological species concept. By Sanger sequencing of a large collection of morphospecies, this study presents the largest database to date of dark-spored myxomycetes and evaluate a partial 18S SSU gene marker for species annotation. We identify and discuss the use of an intraspecific sequence similarity threshold of 99.1% for species differentiation (OTU picking) in environmental PCR studies (ePCR) and estimate a hidden diversity of putative species, exceeding those of described morphospecies by 99%. When applying the identified threshold to an ePCR dataset (including sequences from both NGS and cloning) we find 64 OTUs of which 21.9% had a direct match (> 99.1% similarity) to the database and the remaining had on average 90.2 ± 0.8% similarity to their best match, thus thought to represent undiscovered diversity of dark-spored myxomycetes. This article is protected by copyright. All rights reserved.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/1755-0998.12725