pulmonaria, intermingled

with other bacteria (Fig. 1). Burkholderia is present in the culturable fraction but hardly detected by in situ hybridization (Cardinale et al., 2006, 2008). Isolates of Burkholderia were retrieved from the same lichen samples used in this work (data not shown). Although evidences of either symbiotic relationship or pathogenicity were not yet shown in the lichen hosts, strains of Burkholderia are selleck chemical already known for their stable associations and symbiosis with fungi, such as mycorhiza (Partida-Martinez et al., 2007). Considering the protective and self-sustaining nature of the lichen symbiosis, it can be hypothesized that some of the lichen-associated Burkholderia strains play functional roles, as already proved in other fungal-Burkholderia associations, such as enabling the vegetative reproduction (Partida-Martinez et al., 2007) or supporting the nutrient uptake (Ruiz-Lozano & Bonfante, 1999) and pathogen defence (Opelt et al., 2007). We also analysed the diversity of nifH genes, which is related to the functional

group of nitrogen fixers. They include the Nostoc symbionts and further potential N-fixing species. The ability to grow on N-free substrate was already shown for bacterial strains belonging to different classes, isolated from different species of lichens (Cardinale et al., 2006; Grube et al., 2009). Grube & Berg (2009) suggested that, in the case of N-limiting conditions, bacterial N-fixation could be of considerable importance for the vitality of lichens. To test our hypothesis, we considered the theoretical pattern of distribution proposed by Hughes Martiny et al. (2006) as a consequence Raf inhibitor of prevailing historical or environmental influences. Lobaria pulmonaria

has very strict requirements for growing, so that the environmental parameters cannot differ very much across sites where it grows. Its associated bacteria live in their habitat (the thallus) where the environmental parameters are even more stable, because of the homeostatic effect generated by the hosting organism. The assumption of our study was that the lichen Lobaria offers a similar habitat, even across very distant regions. The lichen should thus represent one single ‘microbial habitat’ and the only differences O-methylated flavonoid between structures of bacterial taxa associated with lichen samples from different regions would result from historical contingencies as a biogeographical effect. Lichen samples were collected from northern Styria (47°37′35″ N, 14°41′35″ E), southern Styria (46°44′35″ N, 15°04′30″ E), Montenegro (42°53′55″ N, 19°35′51″ E) and Madeira (32°44′09″ N, 16°53′17″ W). These locations lie within a range of relative distances (102.4–3367 km) that allows the occurrence of both historical contingencies and contemporary environmental factors (Hughes Martiny et al., 2006). Four to seven independent replicates (composite samples of four lichen thalli) per sampling site were collected.