Abstract
The microbial diversity and function of terrestrial lichens have been well studied, but knowledge about the non-photosynthetic bacteria associated with marine lichens is still scarce. 16S rRNA gene Illumina sequencing was used to assess the culture-independent bacterial diversity in the strictly marine cyanolichen species Lichina pygmaea and Lichina confinis, and the maritime chlorolichen species Xanthoria aureola which occupy different areas on the littoral zone. Inland terrestrial cyanolichens from Austria were also analysed as for the marine lichens to examine further the impact of habitat/lichen species on the associated bacterial communities. The L. confinis and L. pygmaea communities were significantly different from those of the maritime Xanthoria aureola lichen found higher up on the littoral zone and these latter communities were more similar to those of the inland terrestrial lichens. The strictly marine lichens were dominated by the Bacteroidetes phylum accounting for 50% of the sequences, whereas Alphaproteobacteria, notably Sphingomonas, dominated the maritime and the inland terrestrial lichens. Bacterial communities associated with the two Lichina species were significantly different sharing only 33 core OTUs, half of which were affiliated to the Bacteroidetes genera Rubricoccus, Tunicatimonas and Lewinella, suggesting an important role of these species in the marine Lichina lichen symbiosis. Marine cyanolichens showed a higher abundance of OTUs likely affiliated to moderately thermophilic and/or radiation resistant bacteria belonging to the Phyla Chloroflexi, Thermi, and the families Rhodothermaceae and Rubrobacteraceae when compared to those of inland terrestrial lichens. This most likely reflects the exposed and highly variable conditions to which they are subjected daily.
Highlights
The lichen symbiosis, commonly recognised as a partnership of a fungus, and a photosynthetic partner arose with the conquest of land in the lowerHow to cite this article West et al (2018), Marine cyanolichens from different littoral zones are associated with distinct bacterial communities
Analysis of the 20-species mock community allowed us to check for potential contamination and to refine our bioinformatic analysis pipeline to obtain the expected number and identity of OTUs
Using the criteria described in the methods and the algorithm UPARSE of the USEARCH package for clustering OTUs at 97% identity, we obtained 19 OTUs which perfectly corresponded to the mock community plus 17 other OTUs
Summary
The lichen symbiosis, commonly recognised as a partnership of a fungus (mycobiont), and a photosynthetic partner (photobiont) arose with the conquest of land in the lowerHow to cite this article West et al (2018), Marine cyanolichens from different littoral zones are associated with distinct bacterial communities. The lichen symbiosis, commonly recognised as a partnership of a fungus (mycobiont), and a photosynthetic partner (photobiont) arose with the conquest of land in the lower. The enclosure of the photobiont partner by protective layers of the fungal partner gave rise to a new morphological structure. This symbiotic structure is called the lichen thallus, which apparently mediates a high degree of tolerance to desiccation (Kranner et al, 2008), and allows many lichens to thrive as poikilohydric organisms in environments characterised by periodic changes in environmental conditions. Lichens are typically found in habitats where other organisms struggle to persist such as the intertidal belt of coastal rocks, where lichens develop characteristically coloured belts
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