Antarctic Hairgrass Rhizosphere Microbiomes: Microscale Effects Shape Diversity, Structure, and Function (original) (raw)
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Source and acquisition of rhizosphere microbes in Antarctic vascular plants
Frontiers in Microbiology
Rhizosphere microbial communities exert critical roles in plant health, nutrient cycling, and soil fertility. Despite the essential functions conferred by microbes, the source and acquisition of the rhizosphere are not entirely clear. Therefore, we investigated microbial community diversity and potential source using the only two native Antarctic plants, Deschampsia antarctica (Da) and Colobanthus quitensis (Cq), as models. We interrogated rhizosphere and bulk soil microbiomes at six locations in the Byers Peninsula, Livingston Island, Antarctica, both individual plant species and their association (Da.Cq). Our results show that host plant species influenced the richness and diversity of bacterial communities in the rhizosphere. Here, the Da rhizosphere showed the lowest richness and diversity of bacteria compared to Cq and Da.Cq rhizospheres. In contrast, for rhizosphere fungal communities, plant species only influenced diversity, whereas the rhizosphere of Da exhibited higher fung...
Metagenomic exploration of soils microbial communities associated to Antarctic vascular plants
Antarctica is one of the most stressful ecosystems worldwide with few vascular plants, which are limited by abiotic conditions. Here, plants such as Deschampsia antarctica (Da) could generate more suitable micro-environmental conditions for the establishment of other plants as Colobanthus quitensis (Cq). Although, plant-plant interaction is known to determine the plant performance, little is known about how microorganisms might modulate the ability of plants to cope with stressful environmental conditions. Several reports have focused on the possible ecological roles of microorganism with vascular plants, but if the rizospheric microorganisms can modulate the positive interactions among vascular Antarctic plants has been seldom assessed. In this study, we compared the rhizosphere microbiomes associated with Cq, either growing alone or associated with Da, using a shotgun metagenomic DNA sequencing approach and using eggNOG for comparative and functional metagenomics. Overall, results...
Metagenomic Analysis of a Southern Maritime Antarctic Soil
Frontiers in Microbiology, 2012
Our current understanding of Antarctic soils is derived from direct culture on selective media, biodiversity studies based on clone library construction and analysis, quantitative PCR amplification of specific gene sequences and the application of generic microarrays for microbial community analysis. Here, we investigated the biodiversity and functional potential of a soil community at Mars Oasis on Alexander Island in the southern Maritime Antarctic, by applying 454 pyrosequencing technology to a metagenomic library constructed from soil genomic DNA. The results suggest that the commonly cited range of phylotypes used in clone library construction and analysis of 78-730 OTUs (de-replicated to 30-140) provides low coverage of the major groups present (∼5%). The vast majority of functional genes (>77%) were for structure, carbohydrate metabolism, and DNA/RNA processing and modification. This study suggests that prokaryotic diversity in Antarctic terrestrial environments appears to be limited at the generic level, with Proteobacteria, Actinobacteria being common. Cyanobacteria were surprisingly under-represented at 3.4% of sequences, although ∼1% of the genes identified were involved in CO 2 fixation. At the sequence level there appeared to be much greater heterogeneity, and this might be due to high divergence within the relatively restricted lineages which have successfully colonized Antarctic terrestrial environments. Table 2 | Many of the dominant bacterial taxa identified by previous studies on Antarctic soil fall into similar taxonomic categories.
Polar Biology, 2003
Purpose Changes in microbial communities during natural succession in semiarid areas have been widely studied but their association with plant and soil properties remains elusive. In the present study, we investigated plant characteristics, rhizosphere soil variables, and microbial communities along a chronosequence of grasslands forming on abandoned farmland on the Chinese Loess Plateau. Materials and methods Rhizosphere samples were collected from the early-stage dominant plant Artemisia capillaris from farmland abandoned for 5, 10, and 15 years and from the late-stage dominant plant Artemisia sacrorum from farmland abandoned for 10, 15, 20, and 30 years. Microbial community composition, including bacteria and fungi, was determined by highthroughput sequencing. Microbial succession rates represented by temporary turnover were assessed using the slope (w value) of linear regressions, based on log-transformed microbial community similarity over time. Results and discussion Cover and aboveground biomass of A. capillaris tended to decrease, whereas those of A. sacrorum increased during the succession. Although the rhizosphere bacteria of A. capillaris transitioned from Proteobacteria-dominant to Actinobacteria-dominant, the bacteria of A. sacrorum exhibited the opposite trend. Bacterial and fungal community diversity tended to increase logarithmically with increasing plant aboveground biomass, indicating that an increase in plant biomass could lead to enhanced rhizosphere microbial diversity, but the rate of enhancement decreased gradually. A lower temporary turnover rate of bacterial and fungal communities in the rhizosphere than that in the bulk soil indicated a higher successional rate of the rhizosphere microbial community. Levels of soil nutrients, such as organic carbon, nitrate nitrogen, and ammonium nitrogen, were closely associated with the abundance and diversity of bacterial and fungal communities, indicating their critical role in shaping the rhizosphere microbial community. Conclusions Our results indicate a close association between plant succession and rhizosphere microbial succession in a semiarid area. Plants affect the microbial communities possibly by changing the nutrient input into the rhizosphere.
Microbial Ecology
Colobanthus quitensis (Kunth) Bartl. and Deschampsia antarctica Desv. are the only Magnoliophyta to naturally colonize the Antarctic region. The reason for their sole presence in Antarctica is still debated as there is no definitive consensus on how only two unrelated flowering plants managed to establish breeding populations in this part of the world. In this study, we have explored and compared the rhizosphere and root-endosphere dwelling microbial community of C. quitensis and D. antarctica specimens sampled in maritime Antarctica from sites displaying contrasting edaphic characteristics. Bacterial phylogenetic diversity (high-throughput 16S rRNA gene fragment targeted sequencing) and microbial metabolic activity (Biolog EcoPlates) with a geochemical soil background were assessed. Gathered data showed that the microbiome of C. quitensis root system was mostly site-dependent, displaying different characteristics in each of the examined locations. This plant tolerated an active bac...
PLoS ONE, 2013
Understanding the environmental factors that shape microbial communities is crucial, especially in extreme environments, like Antarctica. Two main forces were reported to influence Antarctic soil microbes: birds and plants. Both birds and plants are currently undergoing relatively large changes in their distribution and abundance due to global warming. However, we need to clearly understand the relationship between plants, birds and soil microorganisms. We therefore collected rhizosphere and bulk soils from six different sampling sites subjected to different levels of bird influence and colonized by Colobanthus quitensis and Deschampsia antarctica in Admiralty Bay, King George Island, Maritime Antarctic. Microarray and qPCR assays targeting 16S rRNA genes of specific taxa were used to assess microbial community structure, composition and abundance and analyzed with a range of soil physico-chemical parameters. The results indicated significant rhizosphere effects in four out of the six sites, including areas with different levels of bird influence. Acidobacteria were significantly more abundant in soils with little bird influence (low nitrogen) and in bulk soil. In contrast, Actinobacteria were significantly more abundant in the rhizosphere of both plant species. At two of the sampling sites under strong bird influence (penguin colonies), Firmicutes were significantly more abundant in D. antarctica rhizosphere but not in C. quitensis rhizosphere. The Firmicutes were also positively and significantly correlated to the nitrogen concentrations in the soil. We conclude that the microbial communities in Antarctic soils are driven both by bird and plants, and that the effect is taxa-specific.
Fungal Ecology, 2020
Ice-free regions in coastal areas of Victoria Land, Antarctica, are patchily distributed, limited in extent and characterized by a simple vegetation of lichens and mosses, growing only for a short period during the austral summer. These organisms are associated with soil particles and microorganisms (e.g., algae, microfungi and bacteria) to make up biological soil crusts (BSCs), found worldwide in cold and/or arid and semi-arid regions, where plant growth is impaired. Despite BSCs being among the most widespread ecosystems throughout coastal ice-free areas of continental Antarctica, fungal components of these communities have received little focus. Through ITS1 DNA metabarcoding of samples from 17 sites of six different localities from 73 to 77 S, in a distance scale from 29 to 411 km among different sites, we provide insights into the diversity, community composition, and functionality of fungal communities of these peculiar ecosystems, deepening our knowledge on how they are related to different edaphic variables (i.e. chemical properties and texture). Although fungal richness was low (59 ± 27 OTUs per sample), we found numerous previously unsequenced, putatively unknown fungal species representing a great part of the sampled communities. Community composition was spatially auto-correlated and appeared to be driven by site-specific differences in environmental conditions, particularly edaphic factors, such as exchangeable cations and pH. These results are of particular interest, as they give a wide characterization of the parameters determining soil colonization in a such limiting environment, especially in the light of global changes that are expected to deeply modify the conditions of this environment.
FEMS Microbiology Ecology
Recently, lichens came once more into the scientific spotlight due to their unique relations with prokaryotes. Several temperate region lichen species have been thoroughly explored in this regard yet, the information on Antarctic lichens and their associated bacteriobiomes is somewhat lacking. In this paper, we assessed the phylogenetic structure of the whole and active fractions of bacterial communities housed by Antarctic lichens growing in different environmental conditions by targeted 16S rRNA gene amplicon sequencing. Bacterial communities associated with lichens procured from a nitrogen enriched site were very distinct from the communities isolated from lichens of a nitrogen depleted site. The former were characterized by substantial contributions of Bacteroidetes phylum members and the elusive Armatimonadetes. At the nutrient-poor site the lichen-associated bacteriobiome structure was unique for each lichen species, with chlorolichens being occupied largely by Proteobacteria....