The bacterial communities of Alaskan mosses and their contributions to N2-fixation

Background: Mosses in high-latitude ecosystems harbor diverse bacterial taxa, including N-2-fixers which are key contributors to nitrogen dynamics in these systems. Yet the relative importance of moss host species, and environmental factors, in structuring these microbial communities and their N-2-fixing potential remains unclear. We studied 26 boreal and tundra moss species across 24 sites in Alaska, USA, from 61 to 69 degrees N. We used cultivation-independent approaches to characterize the variation in moss-associated bacterial communities as a function of host species identity and site characteristics. We also measured N-2-fixation rates via N-15(2) isotopic enrichment and identified potential N-2-fixing bacteria using available literature and genomic information. Results: Host species identity and host evolutionary history were both highly predictive of moss microbiome composition, highlighting strong phylogenetic coherence in these microbial communities. Although less important, light availability and temperature also influenced composition of the moss microbiome. Finally, we identified putative N-2-fixing bacteria specific to some moss hosts, including potential N-2-fixing bacteria outside well-studied cyanobacterial clades. Conclusions: The strong effect of host identity on moss-associated bacterial communities demonstrates mosses' utility for understanding plant-microbe interactions in non-leguminous systems. Our work also highlights the likely importance of novel bacterial taxa to N-2-fixation in high-latitude ecosystems.

Automated summary

Host species identity and evolutionary history strongly influence the composition of moss-associated bacterial communities. In addition to host characteristics, light availability and temperature also play a role in shaping the moss microbiome. The study identified potential N-2-fixing bacteria specific to certain moss hosts, emphasizing the importance of novel bacterial taxa in N-2-fixation in high-latitude ecosystems.