Observation Bias in Metabarcoding

Area of Science:

• Molecular Ecology
• Bioinformatics
• Genomics

Background:

• DNA metabarcoding is prone to observation bias from PCR and sequencing.
• Observed read proportions can misrepresent actual species proportions in DNA extracts.

Purpose of the Study:

• To assess and model biases in DNA metabarcoding.
• To identify factors influencing quantitative accuracy in metabarcoding.

Main Methods:

• Amplified and sequenced a mock community of marine fishes and cetaceans.
• Compared metabarcoding observations against expected proportions (total genomic DNA vs. target mitochondrial DNA).
• Modeled PCR amplification bias using species-specific DNA characteristics and PCR protocols.

Main Results:

• Calibrating read proportions with target DNA concentration effectively isolates PCR amplification bias.
• Approximately 60% of remaining bias is explained by DNA characteristics like primer mismatches, amplicon length, and GC content.
• PCR protocols significantly influence community composition, particularly for templates with primer mismatches.

Conclusions:

• Calibrating with target DNA concentration provides more accurate metabarcoding results.
• Minimizing primer-template mismatches and targeting narrow taxonomic groups enhances quantitative accuracy.
• Study findings are crucial for designing reliable quantitative DNA metabarcoding studies.