Quantitative metagenomics for marine prokaryotes and photosynthetic eukaryotes (radA and recA gene databases)

Most sequencing approaches yield only relative microbial abundances, limiting ecological and biogeochemical insights. Here, we present a spike-in quantitative metagenomics to estimate the absolute abundances of prokaryotes and eukaryotic phytoplankton in unfractionated seawater along the Atlantic Meridional Transect. By combining genomic internal standards with single-copy marker genes, this approach enables domain-spanning quantification with genus- to family-level resolution. We have uploaded FASTA files and DIAMOND blastx databases for the single-copy marker genes <i>radA</i> and <i>recA</i>. The <i>recA</i> database has been curated by removing sequences originating from human gut microbiota. To improve taxonomic coverage, we encourage researchers to expand this database with additional <i>recA</i> sequences, particularly from marine environments.