Sphagnum mosses harbour highly specific bacterial diversity during their whole lifecycle

Abstract

Knowledge about Sphagnum-associated microbial communities, their structure and their origin is important to understand and maintain climate-relevant Sphagnum-dominated bog ecosystems. We studied bacterial communities of two cosmopolitan Sphagnum species, which are well adapted to different abiotic parameters (Sphagnum magellanicum, which are strongly acidic and ombrotrophic, and Sphagnum fallax, which are weakly acidic and mesotrophic), in three Alpine bogs in Austria by a multifaceted approach. Great differences between bacterial fingerprints of both Sphagna were found independently from the site. This remarkable specificity was confirmed by a cloning and a deep sequencing approach. Besides the common Alphaproteobacteria, we found a discriminative spectrum of bacteria; although Gammaproteobacteria dominated S. magellanicum, S. fallax was mainly colonised by Verrucomicrobia and Planctomycetes. Using this information for fluorescent in situ hybridisation analyses, corresponding colonisation patterns for Alphaproteobacteria and Planctomycetes were detected. Bacterial colonies were found in high abundances inside the dead big hyalocytes, but they were always connected with the living chlorocytes. Using multivariate statistical analysis, the abiotic factors nutrient richness and pH were identified to modulate the composition of Sphagnum-specific bacterial communities. Interestingly, we found that the immense bacterial diversity was transferred via the sporophyte to the gametophyte, which can explain the high specificity of Sphagnum-associated bacteria over long distances. In contrast to higher plants, which acquire their bacteria mainly from the environment, mosses as the phylogenetically oldest land plants maintain their bacterial diversity within the whole lifecycle.

Effects of nitrogen fertilization on diazotrophic activity of microorganisms associated with Sphagnum magellanicum

“…water table dynamics, O 2 , P and CH 4 availability), are likely to also have contributed to the differences in the diazotrophic communities. Our findings are in contrast to a study comparing the microbial diversity of two Sphagnum species from three sampling sites in the Alps (Bragina et al 2011). There it was observed that the same Sphagnum species from different sites harboured similar microbial communities.…”

“…Sphagnum mosses and their microbial associates have been demonstrated to be specific throughout the moss's life cycle, with a higher microbial diversity observed in Sphagnum species from more eutrophic habitats (Opelt et al 2007;Bragina et al 2011Bragina et al , 2014. The mosses consume carbon dioxide (CO 2 ) produced during decomposition in lower peat layers, while epi-and endophytic microorganisms of Sphagnum contribute additional CO 2 by converting methane (CH 4 ) to CO 2 (Raghoebarsing et al 2005;Kip et al 2011).…”

Next-Generation Bio-Products Sowing the Seeds of Success for Sustainable Agriculture

“…New methods also revealed that seeds are colonized not only by (dormant) pathogenic bacteria, but they also harbor a beneficial seed microbiome. In addition, generative organs like pollen [19] and moss sporophytes [20] harbor a core microbiome, containing potential beneficials, e.g., diazotrophs. Plants are in constant contact with diverse microbes blown by the wind or delivered via the water, and some of them are able to colonize the phyllosphere.…”

Symbiosis revisited: phosphorus and acid buffering stimulate N<sub>2</sub> fixation but not <i>Sphagnum</i> growth

“…On the other end, high atmospheric N deposition may compromise the C sequestration function of peatlands by stimulating microbial processes such as overall decomposition (Bragazza et al, 2006) and denitrification (Gruber and Galloway, 2008). N 2 fixing microorganisms (diazotrophs) live on the surface and inside dead hyaline cells of Sphagnum (Opelt et al, 2007;Bragina et al, 2012;Larmola et al, 2014), forming a symbiosis with their host. A highly diverse microbial community, including Proteobacteria, Verrucomicrobia and Cyanobacteria, has been found to colonize peat mosses (Bragina et al, 2014), and many of these microorganisms have the capacity to fix N 2 (Bragina et al, 2013;Kox et al, 2016).…”