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Bryophytes maintain symbiotic associations with nitrogen-fixing bacteria which can grow epiphytically or endophytically. In this symbiosis, the bacteria supply fixed nitrogen to the plant and they mainly receive photosynthesis and sulfate products from the host. Cyanobacteria are the main group performing nitrogen fixation in bryophyte microbiomes. Nonetheless, other bacterial lineages with nitrogen fixation capabilities have been recently discovered. The number and abundance of bacterial species that compose the bryophyte microbiomes seem to vary according to bryophyte species and environment and host genetic structure. Bryophyte cover in arctic ecosystems represents a principal vegetation type and plays an important role for nitrogen budget through the moss-cyanobacteria associations.
The main purpose of this project is to gain insight into bryophyte-bacterial associations from arctic ecosystems. The moss species Racomitrium lanuginosum (Hedw.) Brid. will be used as model species because it is an abundant clonal moss that occurs in both sub-arctic and arctic ecosystems. The aims of the study are to characterize the microbiome of R. lanuginosum in sub-arctic and arctic Canada; to explore variation in microbial composition and association with host genetic structure; and to assess the nitrogen-fixing capability of the moss-bacteria symbiosis.
The study sites are the area of Kuujjuarapik and the Tursujuq National Park in Nunavik (55°16'28.4520'' N, 77°45'49.6296'' W). They were chosen because of their location in the Canadian arctic tundra and the abundance of the model species (Racomitrium lanuginosum).
In general, the methodology will consist in the use of genotyping by sequencing to infer genetic structure of the host species. Amplicon sequencing will be used to know bacterial groups growing on the moss for the Sub-arctic and Arctic. The use of bioinformatics will help to analyze both, host genetic diversity and microbial diversity. Acetylene essay reduction will be applied to mosses in order to estimate nitrogen fixation for each population.
Populations of Racomitrium lanuginosum may exhibit spatial genetic structure but low genetic diversity within populations due to clonal reproduction. It is expected that microbial diversity varies between populations and according to environmental variation. The nitrogen fixation rates of the moss-microbiome association may differ between sites and in relation to microbial community; nitrogen fixation of the symbiosis could be a main contributor in sub-arctic and arctic ecosystems.