Long-read sequencing of metagenomes from wet deposition samples in the Western USA during an elevated precipitation in February 2019

Abstract

During the month of February in 2019, the Western USA experienced elevated precipitation levels, corresponding to atmospheric river events, ending a drought period. Rainwater samples were collected at four time points across two weeks and analyzed by microscopy, analytical chemistry, and long-read sequencing methods. Quantification of whole cells showed concentrations of > 10⁶ cells/L. Imaged cells from fluorescent and scanning electron microscopy included microeukaryotes. Analytic chemistry detected Na⁺ and Cl⁻ ions, which were in agreement with back trajectories of an oceanic origin and atmospheric river occurrence. Taxonomic investigation of long-read sequences generated from the Nanopore MinION resulted in a high proportion of read assignments to fungal groups. For bacterial taxonomies, common rainwater-associated bacterial genera were present at higher proportions than other bacterial groups: Erwinia, Hymenobacter, Pseudomonas, and Pantoea. The microscopy data support the potential of intact and viable cell wet deposition into local environments and the taxonomic identification of common atmospheric-associated bacterial genera from long-read sequencing highlights the potential usefulness of this platform for atmospheric samples and field campaigns.