Long-Read Metagenomics to Retrieve High-Quality Metagenome-Assembled Genomes from Canine Feces

Background

Metagenomics is a powerful and rapidly developing approach that provides new biological insights into the microbes inhabiting underexplored environments, such as canine fecal microbiome. We investigate long-read metagenomics with Nanopore sequencing to prole the fecal microbiome and to retrieve high-quality metagenome-assembled genomes (HQ MAGs) from a healthy dog.

Results

More than 99% of total classied reads corresponded to Bacteria. The most abundant phylum was Bacteroidetes (~80% of total reads), followed by Firmicutes, Proteobacteria, and Fusobacteria. Prevotella (>50%) and Bacteroides (>20%) are the more abundant genera, followed by Fusobacterium, Megamonas, Sutterella, and other fecal-related genera, (each representing <5% of the total bacterial composition). We retrieved eight single-contig HQ MAGs and three medium-quality MAGs, after combining several metagenome dataset assemblies. The HQ MAGs corresponded to Succinivibrio, Sutterella, Prevotellamassilia, Phascolarctobacterium, Enterococcus, Blautia, and Catenibacterium genera. Succinivibrio HQ MAG represents a novel candidate bacterial species. Sutterella HQ MAG is potentially the rst reported genome assembly for Sutterella stercoricanis, as assigned by 16S rRNA gene similarity. Prevotellamassilia, Phascolarctobacterium, Catenibacterium, and Blautia sp900541345 HQ MAGs improved the contiguity of previously reported genome assemblies in their respective genera, and the number of rRNA genes and tRNA genes. Finally, Enterococcus hirae and Blautia sp003287895 HQ MAGs represented species that already have a complete reference genome. At the technical level, we demonstrated that a high-molecular weight DNA extraction improved the taxonomic classication of the raw unassembled reads, the metagenomics assembly contiguity, and the retrieval of longer and circular contigs, which are potential HQ MAGs.

Conclusions

Long-read metagenomics allowed us to recover HQ MAGs from canine feces of a healthy dog. The high-molecular weight DNA extraction to improve contiguity and the correction of the insertions and deletions to reduce frameshift errors ensure the retrieval of complete single-contig HQ MAGs.