In situ analysis of the bacterial community associated with the reindeer lichen Cladonia arbuscula reveals predominance of Alphaproteobacteria

The diversity and spatial pattern of the bacterial community hosted by the shrub-like reindeer lichen Cladonia arbuscula were investigated by general DNA staining and FISH, coupled with confocal laser scanning microscopy (CLSM). Using an optimized protocol for FISH using cryosections of small lichen fragments, we found about 6 × 107 bacteria g−1 of C. arbuscula. Approximately 86% of acridine orange-stained cells were also stained by the universal FISH probe EUB338. Using group-specific FISH probes, we detected a dominance of Alphaproteobacteria (more than 60% of all bacteria), while the abundance of Actinobacteria and Betaproteobacteria was much lower (<10%). Firmicutes were rarely detected, and no Gammaproteobacteria were present. Bacterial cells of different taxonomic groups are embedded in a biofilm-like, continuous layer on the internal surface of the C. arbuscula podetia, mainly …