Geography, not host identity, shapes bacterial community in reindeer lichens

Abstract

Background and AimsTremendous progress have been recently achieved in host-microbe research, however, there is still a surprising lack of knowledge in many taxa. Despite its dominance and crucial role in boreal forest, reindeer lichens have until now received little attention. We characterize, for the first time, the bacterial community of four species of reindeer lichens from Eastern North America’s boreal forests. We analysed the effect of two factors (host-identity and geography) in the bacterial community composition, we verified the presence of a common core bacteriota and identified the most abundant core taxa.MethodsMorphological and molecular lichen species delimitation was performed based on the ITS region. The bacterial community of around 200 lichen samples was characterised using the 16S rRNA gene.Key ResultsOur results showed that host-lichen identity does not determine bacterial community composition in reindeer lichens, but we confirmed the influence of geography in shaping the diversity and abundance of bacteria associated to the species Cladonia stellaris from lichen woodlands. We also revealed that reindeer lichens share a reduced common core bacteriota composed exclusively by Proteobacteria.ConclusionsThe bacterial community in reindeer lichens is not host-selective. Northern lichen woodlands exhibit a significant higher diversity and abundance of bacteria associated to Cladonia stellaris. Nevertheless, the specific role of those bacteria as well as the process of host colonization remains to be determined. Elucidating these two aspects would be key to have a better understanding of the whole boreal ecosystems. The reduced and not diverse core bacteriota of reindeer lichens might be due to the larger size of our study area. The presence of the species Methylorosula polaris in the core bacteriota is evident and might have a particular importance for reindeer lichens.

Microbial Communities of Cladonia Lichens and Their Biosynthetic Gene Clusters Potentially Encoding Natural Products

“…Nevertheless, bacterial communities dominated by Acidobacteria (followed by Alphaproteobacteria, Gammaproteobacteria, Actinobacteria, Planctomycetes, and Verrucomicrobia) have been previously described for Cladonia thalli based on amplicon sequencing analysis [ 97 ]. Recent studies using high-throughput DNA sequencing of microbial communities have also confirmed the predominance of Alphaproteobacteria among the non-phototrophic bacteria in many other lichens [ 12 , 74 , 75 , 83 , 86 , 98 , 99 , 100 ].…”

“…The lichenised fungal genus Cladonia has an almost cosmopolitan distribution and has been the target of many taxonomic and ecological studies over the years [ 29 ]. Recently, investigations on lichen microbial communities have expanded our knowledge of the diversity of eukaryotes and prokaryotes living in the lichen thalli [ 2 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 ]. Here, we used OTU amplicon sequencing of bacteria (16S rRNA V3-V4 gene region) and fungi/microalgae (ITS2 region) to observe the diversity of microbial communities present in the thalli of six Cladonia specimens collected from boreal forest and urban area environments in Southern Finland.…”

“…While the microbial diversity of Cladonia lichens has been reported to depend on the mycobiont species [ 84 ], a lack of such specificity was found among Cladonia mitis , Cladonia stellaris , Cladonia rangiferina , and Cladonia stygia [ 86 ]. Furthermore, the latter study indicates the influence of geography in the diversity and abundance of bacteria living in reindeer lichens [ 86 ].…”

“…While the microbial diversity of Cladonia lichens has been reported to depend on the mycobiont species [ 84 ], a lack of such specificity was found among Cladonia mitis , Cladonia stellaris , Cladonia rangiferina , and Cladonia stygia [ 86 ]. Furthermore, the latter study indicates the influence of geography in the diversity and abundance of bacteria living in reindeer lichens [ 86 ]. Taken together, our findings on the bacterial diversity within the six lichen specimens are consistent with these previous results and parallel DNA-sequencing-based community studies of Cladonia lichens.…”