An efficient and robust laboratory workflow and tetrapod database for larger scale environmental DNA studies
Research article published in GigaScience (2019)
Abstract
BACKGROUND: The use of environmental DNA for species detection via metabarcoding is growing rapidly. We present a co-designed lab workflow and bioinformatic pipeline to mitigate the 2 most important risks of environmental DNA use: sample contamination and taxonomic misassignment. These risks arise from the need for polymerase chain reaction (PCR) amplification to detect the trace amounts of DNA combined with the necessity of using short target regions due to DNA degradation. FINDINGS: Our high-throughput workflow minimizes these risks via a 4-step strategy: (i) technical replication with 2 PCR replicates and 2 extraction replicates; (ii) using multi-markers (12S,16S,CytB); (iii) a "twin-tagging," 2-step PCR protocol; and (iv) use of the probabilistic taxonomic assignment method PROTAX, which can account for incomplete reference databases. Because annotation errors in the reference sequences can result in taxonomic misassignment, we supply a protocol for curating sequence datasets. For some taxonomic groups and some markers, curation resulted in >50% of sequences being deleted from public reference databases, owing to (i) limited overlap between our target amplicon and reference sequences, (ii) mislabelling of reference sequences, and (iii) redundancy. Finally, we provide a bioinformatic pipeline to process amplicons and conduct PROTAX assignment and tested it on an invertebrate-derived DNA dataset from 1,532 leeches from Sabah, Malaysia. Twin-tagging allowed us to detect and exclude sequences with non-matching tags. The smallest DNA fragment (16S) amplified most frequently for all samples but was less powerful for discriminating at species rank. Using a stringent and lax acceptance criterion we found 162 (stringent) and 190 (lax) vertebrate detections of 95 (stringent) and 109 (lax) leech samples. CONCLUSIONS: Our metabarcoding workflow should help research groups increase the robustness of their results and therefore facilitate wider use of environmental and invertebrate-derived DNA, which is turning into a valuable source of ecological and conservation information on tetrapods.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Zusammenfassung
The use of environmental DNA for species detection via metabarcoding is growing rapidly.
Warum dies für die Hirudotherapie relevant ist
This study presents a laboratory workflow and bioinformatic pipeline for environmental DNA metabarcoding designed to mitigate sample contamination and taxonomic misassignment through technical replication, multi-marker approaches (12S, 16S, CytB), twin-tagging PCR, and probabilistic taxonomic assignment via PROTAX. The pipeline was tested on invertebrate-derived DNA from 1,532 leeches from Sabah, Malaysia, yielding 162 vertebrate detections under stringent criteria (from 95 leech samples) and 190 under lax criteria (from 109 leech samples). Leeches here function as passive collectors of vertebrate DNA for ecological and conservation monitoring rather than as subjects of therapeutic or secretome research. This work has no direct relevance to hirudotherapy or ASH's domain.
Zitation
An efficient and robust laboratory workflow and tetrapod database for larger scale environmental DNA studies
Axtner J et al. · GigaScience, 2019
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