Raccoons foster the spread of freshwater and terrestrial microorganisms-Mammals as a source of microbial eDNA

Aim The aim of the study was to test the role of racoon (Procyon lotor), an invasive alien species, in the spread of microorganisms. We tested whether the spread of microorganisms can be detected by sampling microbial DNA sourced from the raccoon body, thus facilitating biodiversity research. Location Warta Mouth National Park, western Poland. Methods We used the V4 hyper-variable region of the 18S ribosomal RNA gene and Illumina MiSeq amplicon sequencing to identify microorganisms present on the body surface of raccoons. Results Out of 170 DNA samples, we obtained 15 PCR products that contained the target sequences of freshwater or terrestrial microorganisms. We found that raccoons carry and spread chlorophytes, alveolates, amoeboids and fungi on their body surface. We identified 16 different microbial organisms. The sequences of four organisms, Micronuclearia podoventralis (amoeboid), Parachloroidium lobatum and Jaagichlorella roystonensis (chlorophyta), and Mortierella polygonia (fungi), exhibited 100% identity to the best GenBank hit and were thus identified to the species level. The two chlorophyte species, Parachloroidium lobatum and Jaagichlorella roystonensis, are particularly noteworthy, as they were first described recently, in 2013 and 2019, respectively, and knowledge about their global distribution is very scarce. Main conclusions We demonstrated that raccoons may effectively spread terrestrial and aquatic microorganisms. By utilizing this novel source of microbial DNA, we also showed that mammals may be effective living samplers. This perspective is worth exploring, as in some cases it may efficiently reduce the burden required in traditional sampling and provide valuable insights into local biodiversity and distributions of species.