Microbial diversity associated with Sphagnum mosses

Bryophytes belong to the phylogenetically oldest land plants. The bryophyte genus Sphagnum is the dominant component of the mire and bog vegetation, which are of high importance for our world climate. Recently, it was shown that Sphagnum mosses are colonized in high abundances with special microbial communities, which fulfil important functions for the moss plantlets as well as for the whole bog ecosystem. However, data obtained resulted in a lot of new scientific questions; which are the objective of this joint project. These are the following analyses of 1) specificity of Sphagnum associated microbial communities world wide, 2) transmission of bacteria by spores, 3) spatial structure of Sphagnum associated microbes using FISH (Fluorescence in situ hybridization) and CLSM (confocal laser scanning microscopy), and, 4) assessment of biotechnological potential of Sphagnum-associated isolates. Altogether, results should lead in a new understanding of this interesting bio-resource.

Mosses of the genus Sphagnum are among the most abundant and cosmopolitan of bog vegetation in the Northern Hemisphere and greatly contribute to both global carbon turnover and global climate. Despite the importance of these peat mosses in the biosphere, their microbiome remains poorly defined. In this project, we investigated microbial communities of two Sphagnum mosses in Austrian and Russian bogs with a special focus on their ecology and potential for biotechnological applications.Host specificity of moss-associated microbiomes was detected independent of geographic region at both structural and functional levels using different approaches. The degree of host specificity varied between distant and closely related moss species and corresponded to spectra of secondary metabolites produced by plants. Moreover, environmental factors such as acidity and nutrient richness were defined as the main ecological drivers for microbial diversity. For the first time, we showed plant specificity of functional bacterial groups as determined by their role within the ecosystem, particularly nitrogen-fixing and methane-oxidising bacteria. Furthermore, visualisation of the intact plant-microbial consortia revealed dense and well-structured microbial colonisation patterns in/on Sphagnum plants, and stems and leaves of mosses were occupied by various taxonomic groups of bacteria. Notably, we showed that associated microbial communities are maintained during the entire lifecycle of the host plants which contributes to the host specificity. Additionally, the core microbiome not only contained mostly beneficials, but was also shared between the moss generations and transferred within the spore capsules which emphasize the importance of the microbiome for mosses as the oldest phylogenetic land plants on Earth.In parallel to basic research, moss-associated bacteria were evaluated for application in biotechnology. A large portion of bacteria isolated from the moss tissues contained high antagonistic activity against phytopathogens, and Sphagnum-associated bacteria were found to be excellent plant colonizers and crop growth promoters. Overall, we demonstrated that Sphagnum mosses harbour highly diverse and specific microbial communities which provide an excellent, yet not fully exploited bio-resource for biotechnological applications.Our results for climate-relevant peatland ecosystems are crucial in understanding ecosystem service, and are also important for applied fields such as nature conservation, climate change, breeding, and biological plant protection strategies.