Alphaproteobacterial communities in geographically distant populations of the lichen Cetraria aculeata

Lichen symbioses were recently shown to include diverse bacterial communities. Although the biogeography of lichen species is fairly well known, the patterns of their bacterial associates are relatively poorly understood. Here we analyse the composition of Alphaproteobacteria in Cetraria aculeata, a common lichen species that occurs at high latitudes and various habitats. Using clone libraries we show that most of the associated Alphaproteobacteria belong to Acetobacteraceae, which have also been found previously in other lichen species of acidic soils and rocks in alpine habitats. The majority of alphaproteobacterial sequences from C. aculeata are very similar to each other and form a single clade. Data from C. aculeata reveal that alphaproteobacterial communities of high latitudes are depauperate and more closely related to each other than to those of extrapolar habitats. This agrees with previous findings for the fungal and algal symbiont in this lichen. Similar to the algal partner, the composition of lichen alphaproteobacterial communities is affected by environmental parameters.