Phylogenetic evaluation of cyanobacteria preserved as historic herbarium exsiccata.

Dried herbarium specimens of cyanobacteria (exsiccata) deposited over 100 years ago were analysed and characterized using combined morphological and molecular approaches. Six representative coccoid and filamentous cyanobacteria from two historic collections and a 15-year-old air-dried environmental sample were studied. Morphological features observed by light and electron microscopy were correlated with the results of 16S rRNA gene sequencing. Historic identifications achieved by means of classical morphology could thus be confirmed by extracted, amplified and sequenced 16S rRNA gene fragments. The results of this study open the possibility of providing genotypic characterizations to botanical type specimens, thus reconciling the botanical and bacteriological approaches to the taxonomic treatment of these micro-organisms.