Accuracy and Completeness of Long Read Metagenomic Assemblies

Area of Science:

• Microbiology
• Bioinformatics
• Genomics

Background:

• Microbes significantly impact ecosystems and human health.
• Metagenomics enables the study of microbial interactions.
• Long-read nanopore sequencing offers advancements in metagenomic assembly accuracy.

Purpose of the Study:

• To benchmark the performance of three long-read assemblers (Flye, Raven, Redbean) for metagenomic assembly.
• To evaluate the impact of increased read accuracy and depth on assembly quality.
• To determine the most effective assembler for recovering both chromosomal and plasmid DNA.

Main Methods:

• A DNA standard of seven bacteria was used as the input community.
• Sequencing was performed using VolTRAX V2 and MinION mk1b with nanopore technology.
• Basecalling was done with Guppy v5.0.7 (super-accuracy model), and assemblies were polished with Medaka.
• Performance was assessed based on read depth and assembler efficiency.

Main Results:

• All assemblers benefited from increased read depth, with near-complete chromosome recovery at 10× depth.
• Medaka polishing predictably enhanced assembly quality.
• Flye demonstrated superior robustness across taxa and was most effective at plasmid recovery.

Conclusions:

• Flye is recommended for future metagenomic studies due to its consistent chromosome assembly and enhanced plasmid recovery capabilities.
• Increased nanopore read accuracy, combined with sufficient read depth, facilitates accurate metagenomic assembly.
• Benchmarking is crucial for selecting optimal bioinformatics tools for specific research questions.