Metagenomic analysis of historical herbarium specimens reveals a postmortem microbial community

Advances in DNA extraction and next-generation sequencing (NGS) make a vast number of historical herbarium specimens available for genomic investigation. These specimens contain not only genomic information from the specimen itself, but also from associated microorganisms like bacteria and fungi. These microorganisms may have colonized the living plant, e.g. pathogens or host-associated commensal taxa, or may result from postmortem colonization that may include decomposition processes or contamination during sample handling. We here characterize the metagenomic profile from shotgun sequencing data from herbarium specimens of two widespread plant species (Ambrosia artemisiifolia and Arabidopsis thaliana) collected up to 180 years ago. We used BLAST searching in combination with MEGAN and were able to infer the metagenomic community even from the oldest herbarium sample