Scaling up by looking closer: extending the range of moss-Nostoc symbioses deeper into central Europe and to new moss hosts in the forest canopy.

Abstract

Since their re-discovery, Moss-cyanobacterial symbioses are of increasing interest, especially Nostoc-feather-moss symbioses. Efforts to document Nostoc-feather-moss symbioses have historically been centered in Scandinavia and the North American Boreal forest zone. Herein we report the results of several opportunistic surveys investigating the occurrence of Nostoc-moss symbioses in the region of Franconia (Germany). Using culture- and microscopy-based methods, we confirm the occurrence of such symbioses in our region. Two new moss host species of the epiphytic family Orthotrichaceae, Orthotrichum and Zygodon, are also documented, further extending the range of known moss hosts for Nostoc-like organisms outside the traditional feather moss (Hypnales) and Sphagnum clades. Full length 16S sequence alignments placed the moss-associated Nostoc-like organisms throughout our Nostocaceae phylogeny, with no obvious single symbiotic clade. We note the presence of multiple alternate nifH genes within the genomes of single Nostoc-like organisms, possibly enabling diazotrophy under variable ecological conditions. We also present evidence for possible endophytic colonization by cyanobacteria of stems of mosses.