Habitat conditions and not moss composition mediate microbial community structure in Swiss peatlands.

Peatlands, one of the oldest ecosystems, globally store significant amounts of carbon and freshwater. However, they are under severe threat from human activities, leading to changes in water, nutrient and temperature regimes in these delicate systems. Such shifts can trigger a substantial carbon flux into the atmosphere and diminish the water-holding capacity of peatlands. Microbes associated with moss in peatlands play a crucial role in providing these ecosystem services, which are at risk due to global change. Therefore, understanding the factors influencing microbial composition and function is vital. Our study focused on five peatlands along an altitudinal gradient in Switzerland, where we sampled moss on hummocks containing Sarracenia purpurea. Structural equation modelling revealed that habitat condition was the primary predictor of community structure and directly influenced other environmental variables. Interestingly, the microbial composition was not linked to the local moss species identity. Instead, microbial communities varied significantly between sites due to differences in acidity levels and nitrogen availability. This finding was also mirrored in a co-occurrence network analysis, which displayed a distinct distribution of indicator species for acidity and nitrogen availability. Therefore, peatland conservation should take into account the critical habitat characteristics of moss-associated microbial communities.

Screening of endophytic fungi from Antarctic mosses: Potential production for L-asparaginase free of glutaminase and urease activity.

Studies involving endophytic fungi aim to identify organisms inhabiting extreme and relatively unexplored environments, as these fungi possess unique characteristics and uncommon biochemical pathways that enable them to produce compounds with biotechnological potential. Among various enzymes, L-Asparaginase is employed in the treatment of Acute Lymphoblastic Leukemia. In this study, we identified endophytic fungi from Sanionia uncinata and Polytrichastrum alpinum collected on King George Island in Antarctica. The fungi were categorized into morphological groups based on their characteristics, molecularly identified, and assessed for L-Asparaginase (L-ASNase) enzyme production. Subsequently, production optimization was conducted. A total of 161 endophytes were isolated from 504 moss gametophytes, with 107 originating from P. alpinum and 54 from S. uncinata. These isolates were categorized into 31 morphotypes. Fungi exhibiting high enzyme production were identified molecularly. Among them, nine identified isolates belonged to the genera Aspergillus, Collariella, Diaporthe, Epicoccum, Peroneutypa, Xylaria, and Trametes. Three of these isolates were identified at the species level through multigene phylogeny, namely Epicoccum nigrum, Collariella virescens, and Peroneutypa scoparia. All 31 fungi were subjected to solid media testing for L-ASNase enzyme production, with 22 isolates demonstrating production capability, and 13 of them produced L-ASNase free from Urease and Glutaminase. The isolates displaying solid media production underwent further testing in liquid media, all of which exhibited enzyme production ranging from 0.75 to 1.29 U g-1. Notably, the three fungi identified at the species level were the highest producers of the enzyme (1.29, 1.17, and 1.13 U g-1). The production of these fungi was optimized using the Taguchi method, resulting in production values ranging from 0.687 to 2.461 U g-1. In conclusion, our findings indicate that Antarctic moss endophytic fungi exhibit significant potential for the production of the anti-leukemic enzyme L-ASNase.

Unraveling global and diazotrophic bacteriomes of boreal forest floor feather mosses and their environmental drivers at the ecosystem and at the plant scale in North America.

Feather mosses are abundant cryptogams of the boreal forest floor and shelter a broad diversity of bacteria who have important ecological functions (e.g., decomposition, nutrient cycling). In particular, nitrogen (N2-) fixation performed by feather moss-associated diazotrophs constitutes an important entry of nitrogen in the boreal forest ecosystem. However, the composition of the feather moss bacteriome and its environmental drivers are still unclear. Using cDNA amplicon sequencing of the 16S rRNA and nifH genes and cyanobacterial biomass quantification, we explored the active global and diazotrophic bacterial communities of two dominant feather moss species (i) at the ecosystem scale, along a 500-km climatic and nutrient deposition gradient in the North American boreal forest, and (ii) at the plant scale, along the moss shoot senescence gradient. We found that cyanobacteria were major actors of the feather moss bacteriome, accounting for 33% of global bacterial communities and 65% of diazotrophic communities, and that several cyanobacterial and methanotrophic genera were contributing to N2-fixation. Moreover, we showed that bacteria were occupying ecological niches along the moss shoot, with phototrophs being dominant in the apical part and methanotrophs being dominant in the basal part. Finally, climate (temperature, precipitation), environmental variables (moss species, month, tree density) and nutrients (nitrogen, phosphorus, molybdenum, vanadium, iron) strongly shaped global and diazotrophic bacteriomes. In summary, this work presents evidence that the feather moss bacteriome plays crucial roles in supporting moss growth, health, and decomposition, as well as in the boreal forest carbon and nitrogen cycles. This study also highlights the substantial effects of climate and nutrients on the feather moss bacteriome, suggesting the importance of understanding the impacts of global change on moss-associated bacterial growth and activity.

Dominance of coniferous and broadleaved trees drives bacterial associations with boreal feather mosses.

The composition of ecologically important moss-associated bacterial communities seems to be mainly driven by host species but may also be shaped by environmental conditions related with tree dominance. The moss phyllosphere has been studied in coniferous forests while broadleaf forests remain understudied. To determine if host species or environmental conditions defined by tree dominance drives the bacterial diversity in the moss phyllosphere, we used 16S rRNA gene amplicon sequencing to quantify changes in bacterial communities as a function of host species (Pleurozium schreberi and Ptilium crista-castrensis) and forest type (coniferous black spruce versus deciduous broadleaf trembling aspen) in eastern Canada. The overall composition of moss phyllosphere was defined by the interaction of both factors, though most of the bacterial phyla were determined by a strong effect of forest type. Bacterial α-diversity was highest in spruce forests, while there was greater turnover (ß-diversity) and higher γ-diversity in aspen forests. Unexpectedly, Cyanobacteria were much more relatively abundant in aspen than in spruce forests, with the cyanobacteria family Nostocaceae differing the most between forest types. Our results advance the understanding of moss-associated microbial communities among coniferous and broadleaf deciduous forests, which are important with the increasing changes in tree dominance in the boreal system.

Bog ecosystems as a playground for plant-microbe coevolution: bryophytes and vascular plants harbour functionally adapted bacteria.

BACKGROUND: Bogs are unique ecosystems inhabited by distinctive, coevolved assemblages of organisms, which play a global role for carbon storage, climate stability, water quality and biodiversity. To understand ecology and plant-microbe co-occurrence in bogs, we selected 12 representative species of bryophytes and vascular plants and subjected them to a shotgun metagenomic sequencing approach. We explored specific plant-microbe associations as well as functional implications of the respective communities on their host plants and the bog ecosystem. RESULTS: Microbial communities were shown to be functionally adapted to their plant hosts; a higher colonization specificity was found for vascular plants. Bryophytes that commonly constitute the predominant Sphagnum layer in bogs were characterized by a higher bacterial richness and diversity. Each plant group showed an enrichment of distinct phylogenetic and functional bacterial lineages. Detailed analyses of the metabolic potential of 28 metagenome-assembled genomes (MAGs) supported the observed functional specification of prevalent bacteria. We found that novel lineages of Betaproteobacteria and Actinobacteria in the bog environment harboured genes required for carbon fixation via RuBisCo. Interestingly, several of the highly abundant bacteria in both plant types harboured pathogenicity potential and carried similar virulence factors as found with corresponding human pathogens. CONCLUSIONS: The unexpectedly high specificity of the plant microbiota reflects intimate plant-microbe interactions and coevolution in bog environments. We assume that the detected pathogenicity factors might be involved in coevolution processes, but the finding also reinforces the role of the natural plant microbiota as a potential reservoir for human pathogens. Overall, the study demonstrates how plant-microbe assemblages can ensure stability, functioning and ecosystem health in bogs. It also highlights the role of bog ecosystems as a playground for plant-microbe coevolution. Video abstract.

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

BACKGROUND: Mosses in high-latitude ecosystems harbor diverse bacterial taxa, including N2-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 N2-fixing potential remains unclear. We studied 26 boreal and tundra moss species across 24 sites in Alaska, USA, from 61 to 69° 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 N2-fixation rates via 15N2 isotopic enrichment and identified potential N2-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 N2-fixing bacteria specific to some moss hosts, including potential N2-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 N2-fixation in high-latitude ecosystems. Video Abstract.

New terpenoids and triketides from culture of the fungus Botrysphaeria laricina.

Three new isopimarane-type diterpenoids, botrysphins G-I (1-3), a new muurolane-type sesquiterpenoid, 11,12-dihydroxylentideusether (4), and two new triketides, 4-dechlorobotrysphone C (5) and 4,5-dihydroxy-3-methoxy-6-undecanoyloxy-2-cyclohexen-1-one (6), together with one known diterpenoid, sphaeropsidin A (7), one sesquiterpenoid, lentideusether (8), and one triketide sphaeropsidone (9), were isolated from culture of the fungus Botrysphaeria laricina associated with the moss Rhodobryum umgiganteum. The structures of the new compounds were established on the basis of extensive spectroscopic techniques including HRMS and 1D and 2D NMR data. Compounds 1 and 2 exhibited NO inhibitory activity with IC50 values of 13.9 µM and 41.9 µM, respectively. At the same time, these two compounds showed quinone reductase inducing activity with 2.7-fold of induction for 1 at 12.5 µM and 1.6-fold for 2 at 25.0 µM.

Novel secondary metabolites from the endobryophytic fungus Botrysphaeria laricina and their biological activity.

One novel polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) hybrid metabolite, laricinin A (1), two new meroterpenoids, tricycloalternarenes X and Y (2 and 3), one new coumarin, 3,4,7-trihydroxy-6-methylcoumarin (4), together with the known ethyl acetylorsellinate (5), diorcinol K (6), and tricycloalternarenes C and D (7 and 8) were obtained from culture of the fungus Botrysphaeria laricina isolated from the moss Rhodobryum umgiganteum. The structures of the new compounds were elucidated based on extensive spectroscopic techniques including HRMS and 1D and 2D NMR measurements. The absolute configuration of compound 1 was determined by ECD calculation and it was the first example of a novel group of PKS-NRPS hybrids possessing an unprecedented methyldihydropyran-isobutylpyrrolidinone skeleton. Compounds 2, 7, and 8 showed significant quinone reductase inducing activity in Hepa 1c1c7 cells.

Cross-kingdom signalling regulates spore germination in the moss Physcomitrella patens.

Plants live in close association with microorganisms that can have beneficial or detrimental effects. The activity of bacteria in association with flowering plants has been extensively analysed. Bacteria use quorum-sensing as a way of monitoring their population density and interacting with their environment. A key group of quorum sensing molecules in Gram-negative bacteria are the N-acylhomoserine lactones (AHLs), which are known to affect the growth and development of both flowering plants, including crops, and marine algae. Thus, AHLs have potentially important roles in agriculture and aquaculture. Nothing is known about the effects of AHLs on the earliest-diverging land plants, thus the evolution of AHL-mediated bacterial-plant/algal interactions is unknown. In this paper, we show that AHLs can affect spore germination in a representative of the earliest plants on land, the Bryophyte moss Physcomitrella patens. Furthermore, we demonstrate that sporophytes of some wild isolates of Physcomitrella patens are associated with AHL-producing bacteria.

Ammonia Oxidation Potentials and Ammonia Oxidizers of Lichen-Moss Vegetated Soils at Two Ice-free Areas in East Antarctica.

The maximum ammonia oxidation potential (AOP) of a topsoil in Langhovde, East Antarctica was 22.1±2.4| |ng N g-1 dry soil h-1 (2| |mM ammonium, 10°C, n=3). This topsoil exhibited twin AOP peaks (1 and 2| |mM ammonium) at 10°C, but not at 20°C. Six and ten operational taxonomic units (OTUs) were identified for ammonia-oxidizing bacteria (AOB) and archaea (AOA) amoA, respectively. AOB were classified into Nitrosospira; the two dominant OTUs corresponded to the Mount Everest cluster. AOA were classified into three clusters; Nitrososphaera and Nitrosocosmicus were the two dominant clusters.

Taxonomic study of Endogonaceae in the Japanese islands: New species of Endogone, Jimgerdemannia, and Vinositunica, gen. nov.

Species of Endogonaceae (Endogonales, Mucoromycotina) are characterized by the formation of relatively large sporocarps and zygosporangia. Numerous species in this family remain undescribed or have unclear phylogenetic positions. In Asia specifically, the species diversity of this family is almost completely unknown. However, many mycobionts of bryophytes belonging to several novel clades in Endogonaceae have recently been identified phylogenetically. Therefore, establishing a robust taxonomic system for this family is essential. We obtained numerous sporocarps of undescribed Endogonaceae-like species from the Japanese islands. Morphological observation and multilocus phylogenetic analysis of nuc 18S rDNA (18S), nuc 28S rDNA (28S), and portions of two nuclear protein-coding regions-translation elongation factor 1-alpha (tef1) and RNA polymerase II large subunit (rpb1)-from these species resulted in the description of one new species each of Endogone and Jimgerdemannia and two new species of Vinositunica, gen. nov. Because Vinositunica is characterized by purplish sporocarps and red-wine-colored chlamydospores up to 700 µm in diameter, we emended the definition of Endogonaceae.

Actinomadura physcomitrii sp. nov., a novel actinomycete isolated from moss [Physcomitrium sphaericum (Ludw) Fuernr].

A novel endophytic actinomycete, designated strain LD22T, was isolated from moss [Physcomitrium sphaericum (Ludw) Fuernr] collected from Yunnan Province, Southwest China. A polyphasic taxonomic study was carried out to establish the status of this strain. Morphological and chemotaxonomic characteristics of strain LD22T confirmed the affiliation of the isolate to the genus Actinomadura. The diamino acid present in the cell wall is meso-diaminopimelic acid. Glucose, madurose, galactose and ribose occur in whole cell hydrolysates. The menaquinones were identified as MK-9(H4), MK-9(H8), MK-9(H6) and MK-9(H2). The polar lipid profile was found to contain diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside and an unidentified phospholipid. The major fatty acids were found to be C16:0, 10-methyl C18:0 and C18:1 ω9c. The DNA G + C content of the draft genome sequence, consisting of 10.0 Mbp, was 72.5%. Phylogenetic analysis of 16S rRNA gene sequences showed that strain LD22T belongs to the genus Actinomadura with the highest sequence similarity to Actinomadura montaniterrae CYP1-1BT (99.2%). However, phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate formed a phyletic line with Actinomadura rudentiformis HMC1T (98.6%). The low level of DNA-DNA relatedness and some different phenotypic characteristics allowed the strain to be distinguished from the above-mentioned two strains. Therefore, it is concluded that strain that strain LD22T represents a novel species of the genus of Actinomadura, for which the name Actinomadura physcomitrii sp. nov. is proposed. The type strain is LD22T (= CCTCC AA 2018050T = JCM 33455T).

Bryophytes and the symbiotic microorganisms, the pioneers of vegetation restoration in karst rocky desertification areas in southwestern China.

In karst rocky desertification areas, bryophytes coexist with algae, bacteria, and fungi on exposed calcareous rocks to form a bryophyte crust, which plays an irreplaceable role in the restoration of karst degraded ecosystems. We investigated the biodiversity of crust bryophytes in karst rocky desertification areas from Guizhou Province, China. A total of 145 species in 22 families and 56 genera were identified. According to frequency and coverage, seven candidate dominant mosses were screened out, and five drought-resistant indexes of them were measured. Hypnum leptothallum, Racopilum cuspidigerum, and Hyophila involuta have high drought adaptability. We explored the interactions between two dominant mosses (H. leptothallum, H. involuta) and the structure of microbial communities in three karst rocky desertification types. Microbial diversity and function analysis showed that both moss species and karst rocky desertification types affect microbial communities. Moss species much more strongly affected the diversity and changed the community composition of these microbial groups. Bacteria were more sensitive in the microbiome as their communities changed strongly between mosses and drought resistance factors. Moreover, several species of fungi and bacteria could be significantly associated with three drought-resistant indexes: Pro (free proline content), SOD (superoxide dismutase activity), and POD (peroxidase activity), which were closely related to the drought adaptability of mosses. Our results enforced the potential role of moss-associated microbes that are important components involved in the related biological processes when bryophytes adapted to arid habitats, or as one kind of promoters in the distribution pattern of early mosses succession in karst rocky desertification areas.

Comparative Characterization of Bacterial Communities in Moss-Covered and Unvegetated Volcanic Deposits of Mount Merapi, Indonesia.

Microbial colonization, followed by succession, on newly exposed volcanic substrates represents the beginning of the development of an early ecosystem. During early succession, colonization by mosses or plants significantly alters the pioneer microbial community composition through the photosynthetic carbon input. To provide further insights into this process, we investigated the three-year-old volcanic deposits of Mount Merapi, Indonesia. Samples were collected from unvegetated (BRD) and moss-covered (BRUD) sites. Forest site soil (FRS) near the volcanic deposit-covered area was also collected for reference. An analysis of BRD and BRUD revealed high culturable cell densities (1.7-8.5×105 CFU g-1) despite their low total C (<0.01%). FRS possessed high CFU (3×106 g-1); however, its relative value per unit of total C (2.6%) was lower than that of the deposit samples. Based on the tag pyrosequencing of 16S rRNA genes, the BRD bacterial community was characterized by a higher number of betaproteobacterial families (or genus), represented by chemolithotrophic Methylophilaceae, Leptothrix, and Sulfuricellaceae. In contrast, BRUD was predominated by different betaproteobacterial families, such as Oxalobacteraceae, Comamonadaceae, and Rhodocyclaceae. Some bacterial (Oxalobacteraceae) sequences were phylogenetically related to those of known moss-associated bacteria. Within the FRS community, Proteobacteria was the most abundant phylum, followed by Acidobacteria, whereas Burkholderiaceae was the most dominant bacterial family within FRS. These results suggest that an inter-family succession of Betaproteobacteria occurred in response to colonization by mosses, followed by plants.

Ecohydrological effects of biocrust type on restoration dynamics in drylands.

Global climate change influences not only vascular plants, but also biological soil crusts (biocrusts), which play important roles in dryland vegetation dynamics by redistributing rainfall in soils. Different types of biocrusts, spanning a spectrum from cyanobacteria-dominated and moss-dominated, have distinct roles in rainfall redistribution patterns, but the ecohydrological effects of different biocrust types on dryland ecosystem dynamics remain largely unclear. This study developed an ecohydrological model with biocrust as a system state variable to explicitly explore the effects of different biocrust types on dryland vegetation dynamics in Shapotou region in northern China, particularly after restoration. The results indicated that both cyanobacteria- and moss-dominated biocrusts could support high grass cover (approximately 40%) after restoration. Cyanobacterial, but not moss biocrusts, could also maintain a high level of shrub cover (13 and 3%, respectively). Shifting from cyanobacteria to mosses gradually increased the biocrust cover from approximately 40% to 80%. The biocrust's water-holding capacity (the volume of water it can intercept per unit area) is likely be able to explain the dynamics of biocrust and shrub cover (with correlation efficiency of R2 = 0.972 and 0.987, respectively), but not grass cover (R2 = 0.224). The findings suggest that biocrust type may significantly affect coverage of biocrusts and shrubs, but not grass coverage, and global climate change may influence dryland restoration by altering biocrust types.

Candida xylosifermentans sp. nov., a d-xylose-fermenting yeast species isolated in Thailand.

Three strains, representing a novel anamorphic and d-xylose-fermenting yeast species, were isolated from moss (ST-302T), seawater (ST-1169) and peat (DMKU-XE12) collected from the southern part of Thailand. The three strains had identical sequences of the D1/D2 regions of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) regions. Candida flosculorum CBS 10566T and Candida sharkiensis CBS 11368T were the most closely related species with 7.9 % nucleotide substitutions in the D1/D2 regions of the LSU rRNA gene, and 10.3 and 12.6% nucleotide substitutions in the ITS regions, respectively. Phylogenetic analysis based on the concatenated sequences of the ITS and the D1/D2 regions confirmed that the three strains represented a distinct anamorphic species in the Clavispora clade. Therefore, the three strains were described as a novel species, for which we propose the name Candida xylosifermentans sp. nov.

Differential gene expression associated with fungal trophic shifts along the senescence gradient of the moss Dicranum scoparium.

Bryophytes harbour microbiomes, including diverse communities of fungi. The molecular mechanisms by which perennial mosses interact with these fungal partners along their senescence gradients are unknown, yet this is an ideal system to study variation in gene expression associated with trophic state transitions. We investigated differentially expressed genes of fungal communities and their host Dicranum scoparium across its naturally occurring senescence gradient using a metatranscriptomic approach. Higher activity of fungal nutrient-related (carbon, nitrogen, phosphorus and sulfur) transporters and Carbohydrate-Active enZyme (CAZy) genes was detected toward the bottom, partially decomposed, layer of the moss. The most prominent variation in the expression levels of fungal nutrient transporters was from inorganic nitrogen-related transporters, whereas the breakdown of organonitrogens was detected as the most enriched gene ontology term for the host D. scoparium, for those transcripts having higher expression in the partially decomposed layer. The abundance of bacterial rRNA transcripts suggested that more living members of Cyanobacteria are associated with the photosynthetic layer of D. scoparium, while members of Rhizobiales are detected throughout the gametophytes. Plant genes for specific fungal-plant communication, including defense responses, were differentially expressed, suggesting that different genetic pathways are involved in plant-microbe crosstalk in photosynthetic tissues compared to partially decomposed tissues.

Microbes Producing L-Asparaginase free of Glutaminase and Urease isolated from Extreme Locations of Antarctic Soil and Moss.

L-Asparaginase (L-asparagine aminohydrolase, E.C. 3.5.1.1) has been proven to be competent in treating Acute Lymphoblastic Leukaemia (ALL), which is widely observed in paediatric and adult groups. Currently, clinical L-Asparaginase formulations are derived from bacterial sources such as Escherichia coli and Erwinia chrysanthemi. These formulations when administered to ALL patients lead to several immunological and hypersensitive reactions. Hence, additional purification steps are required to remove toxicity induced by the amalgamation of other enzymes like glutaminase and urease. Production of L-Asparaginase that is free of glutaminase and urease is a major area of research. In this paper, we report the screening and isolation of fungal species collected from the soil and mosses in the Schirmacher Hills, Dronning Maud Land, Antarctica, that produce L-Asparaginase free of glutaminase and urease. A total of 55 isolates were obtained from 33 environmental samples that were tested by conventional plate techniques using Phenol red and Bromothymol blue as indicators. Among the isolated fungi, 30 isolates showed L-Asparaginase free of glutaminase and urease. The L-Asparaginase producing strain Trichosporon asahii IBBLA1, which showed the highest zone index, was then optimized with a Taguchi design. Optimum enzyme activity of 20.57 U mL-1 was obtained at a temperature of 30 °C and pH of 7.0 after 60 hours. Our work suggests that isolation of fungi from extreme environments such as Antarctica may lead to an important advancement in therapeutic applications with fewer side effects.

Taxonomy and richness of yeasts associated with angiosperms, bryophytes, and meltwater biofilms collected in the Antarctic Peninsula.

The interest in the diversity of yeasts in the Antarctic environment has increased in recent years, mainly because Antarctic microbiology is a recent science, and little is known about the biodiversity and genetic resources of the microorganisms that inhabit this ecosystem. This study aimed to determine the diversity of epiphytic yeasts in samples of Deschampsia antarctica, Colobanthus quitensis, and bryophytes, as well yeasts present in biofilms collected from Antarctic meltwater. Samples were collected in the summer of 2014 and 2015 during expeditions organized by the Brazilian Antarctic Program. A total of 310 yeasts were isolated, and 34 species were identified by sequencing the D1/D2 domains of the rDNA region belonging to 18 genera. The species Vishniacozyma victoriae and Mrakia gelida were the most abundant. Dioszegia antarctica and Leucosporidium creatinivorum were found only in plant substrates. Most psychrophilic yeasts were isolated from biofilms, including Glaciozyma antarctica, Glaciozyma martinii, Mrakia gelida, Mrakia frigida, Mrakia robertii, Phenoliferia glacialis, and Phenoliferia psychrophenolica, suggesting that the substrates examined in this study represented an interesting habitat for the isolation and characterization of epiphytic and non-epiphytic yeasts that colonize the Antarctic region.

Novel bacterial lineages associated with boreal moss species.

Mosses are critical components of boreal ecosystems where they typically account for a large proportion of net primary productivity and harbour diverse bacterial communities that can be the major source of biologically-fixed nitrogen in these ecosystems. Despite their ecological importance, we have limited understanding of how microbial communities vary across boreal moss species and the extent to which local site conditions may influence the composition of these bacterial communities. We used marker gene sequencing to analyze bacterial communities associated with seven boreal moss species collected near Fairbanks, AK, USA. We found that host identity was more important than site in determining bacterial community composition and that mosses harbour diverse lineages of potential N2 -fixers as well as an abundance of novel taxa assigned to understudied bacterial phyla (including candidate phylum WPS-2). We performed shotgun metagenomic sequencing to assemble genomes from the WPS-2 candidate phylum and found that these moss-associated bacteria are likely anoxygenic phototrophs capable of carbon fixation via RuBisCo with an ability to utilize byproducts of photorespiration from hosts via a glyoxylate shunt. These results give new insights into the metabolic capabilities of understudied bacterial lineages that associate with mosses and the importance of plant hosts in shaping their microbiomes.