Biology subjects

Jungblut, A. D.

Publications and source records attributed to Jungblut, A. D..

6 recordsLinked to original sources

bioRxiv2026

Environmental filtering drives cryptic diversity and shifting interaction networks across lake, ephemeral pond, and desiccated microbial mat communities in the Untersee Oasis, East Antarctica

Antarctic lakes and surrounding habitats are natural laboratories for studying microbial ecology in extreme environments, yet assembly and dispersal across these systems remain poorly understood. We analyzed bacterial (16S rRNA) and eukaryotic (18S rRNA) communities across benthic lake mats, pond mats, and desiccated mats around Lake Untersee, East Antarctica. Both domains showed significant environmental differentiation with stochastic assembly dominating, but eukaryotes exhibited stronger habitat-specific structuring. Core microbiomes revealed contrasting strategies: bacteria showed broad colonization with few dominant taxa, while eukaryotes maintained smaller cores anchored by Adineta vaga. Cyanobacterial indicators demonstrated complete strain-level turnover despite uniform phylum dominance. Dispersal patterns diverged strongly: prokaryotes exhibited substantial cross-habitat exchange (28-61%) while eukaryotes showed minimal dispersal (2-16%). Distance-decay relationships revealed significant spatial structuring (bacterial r=0.316-0.70; eukaryotic r=0.43-0.84). Cross-domain networks shifted from facilitative in ponds (65% positive) to competitive under desiccation (54% negative), suggesting resource limitation overrides facilitation at extremes. Functional predictions highlighted habitat specialization: lakes enriched in biogeochemical cycling, desiccated mats in stress tolerance, ponds in CRISPR genes. These findings reveal divergent strategies shaped by environmental filtering, dispersal limitation, and viral interactions, with implications for ecosystem connectivity and resilience. ImportanceAntarctic lake ecosystems serve as natural laboratories for understanding microbial community assembly under extreme conditions, yet connectivity between aquatic and terrestrial habitats remains poorly characterized. This study reveals fundamentally divergent ecological strategies between bacterial and eukaryotic communities across Lake Untersees contrasting environments. While bacteria maintain broad dispersal networks (28-61% cross-habitat exchange) with strain-level habitat specialization, eukaryotes exhibit strong dispersal limitation (2-16% exchange) despite occupying adjacent habitats. Most strikingly, cross-domain interaction networks shift from predominantly facilitative in ephemeral ponds (65% positive associations) to competitive under desiccation stress (54% negative associations), directly challenging the stress gradient hypothesis that predicts cooperation dominates in extreme environments. Combined with habitat-specific functional specialization--from biogeochemical cycling in lakes to stress tolerance in desiccated mats--these findings provide a mechanistic framework for predicting ecosystem connectivity, resilience, and responses to climate-driven habitat transitions in polar regions.

microbiology↗

bioRxiv2022

Biogeographic Distribution of Five Antarctic Cyanobacteria Using Large-Scale k-mer Searching with sourmash branchwater

Cyanobacteria form diverse communities and are important primary producers in Antarctic freshwater environments, but their geographic distribution patterns in Antarctica and globally are still unresolved. There are however few genomes of cultured cyanobacteria from Antarctica available and therefore metagenome-assembled genomes (MAGs) from Antarctic cyanobacteria microbial mats provide an opportunity to explore distribution of uncultured taxa. These MAGs also allow comparison with metagenomes of cyanobacteria enriched communities from a range of habitats, geographic locations, and climates. However, most MAGs do not contain 16S rRNA gene sequences, making a 16S rRNA gene-based biogeography comparison difficult. An alternative technique is to use large-scale k-mer searching to find genomes of interest in public metagenomes. This paper presents the results of k-mer based searches for 5 Antarctic cyanobacteria MAGs from Lakes Fryxell and Lake Vanda, assigned the names Phormidium pseudopriestleyi, a Microcoleus, a Leptolyngbya, a Pseudanabaena, and a Neosynechococcus (Lumian et al., 2021, Lumian et al., 2022, in prep.) in 498,942 unassembled metagenomes from the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA). The Microcoleus MAG was found in a wide variety of environments, P. pseudopriestleyi was found in environments with challenging conditions, the Neosynechococcus was only found in Antarctica, and the Leptolyngbya and Pseudanabaena MAGs were found in Antarctic and other cold environments. The findings based on metagenome matches and global comparisons suggest that these Antarctic cyanobacteria have distinct distribution patterns ranging from locally restricted to global distribution across the cold biosphere and other climatic zones.

microbiology↗

bioRxiv2021

Fungal taste for minerals: the ectomycorrhizal fungus Paxillus involutus triggers specific genes when extracting potassium from different silicates

Silicates make up about 90% of the Earths crust and constitute the main source of mineral nutrients for microorganisms and plants. Fungi can actively weather silicates to extract nutrients. However, it is unclear whether they are able to obtain the same amounts of nutrients and use the same mechanisms when tapping into different mineral sources. We performed a microcosm experiment using the ectomycorrhizal basidiomycetes Paxillus involutus and the silicates K-vermiculite, muscovite and phlogopite as only potassium sources, as they show a different resistance for the removal of K cations from the mineral structure. A combination of transcriptomic, elemental and SEM analyses showed that different minerals stimulated specific weathering mechanisms and led to a change in fungal genes expression. The differential expression of the fungal genes generated alternative chemical attacks on the minerals, resulting in a tailored dissolution and selective uptake of chemical elements according to the leachability of K from the silicate mineral. The K uptake capacity of the fungus was highest with vermiculite in comparison to growth on phlogopite and muscovite. The findings provide new insights into fungal-mineral interactions that will help to interpret key processes for the homeostasis of soil environments.

microbiology↗

bioRxiv2020

Environmental controls and habitat connectivity of phototrophic microbial mats and bacterioplankton communities in an Antarctic freshwater system

Freshwater ecosystems are considered hotspots of biodiversity in Antarctic polar deserts. Anticipated warming is expected to change the hydrology of these systems due to increased meltwater and reduction of ice cover, with implications for environmental conditions and physical connectivity between habitats. Using 16S rRNA sequencing, we evaluated the structure of microbial mat and planktonic communities within a connected watershed in the McMurdo Wright Valley, Antarctica to determine the roles of connectivity and habitat conditions in controlling microbial assemblage composition. We examined benthic and planktonic samples from glacial Lake Brownworth, the perennially ice-covered Lake Vanda, and the Onyx River, which connects the two. In Lake Vanda, we found distinct microbial assemblages occupying sub-habitats at different lake depths, while the communities from Lake Brownworth and Onyx River were structurally similar between them. Despite the higher connectivity between bacterial communities in the shallow parts of the system, environmental filtering dominated over dispersal in driving bacterial community structure. Functional metagenomics predictions identified genes related to degradation of halogenated aromatic compounds in surface microbial mats exposed to changes in water regimes, which progressively disappeared with increasing depth. Shifting environmental conditions due to increasing connectivity, rather than dispersal, may become the dominant drivers of bacterial diversity and functioning in Antarctic freshwater ecosystems.

ecology↗

bioRxiv2019

Long-term warming effects on the microbiome and nitrogen fixation associated with the moss Racomitrium lanuginosum in a subarctic alpine heathland

O_LIBacterial communities form the basis of biogeochemical processes and determine plant growth and health. Mosses, an abundant plant group in Arctic ecosystems, harbour diverse bacterial communities that are involved in nitrogen fixation and carbon cycling. Global climate change is causing changes in aboveground plant biomass and shifting species composition in the Arctic, but little is known about the response of moss microbiomes. C_LIO_LIHere, we studied the total and potentially active bacterial community associated with Racomitrium lanuginosum, in response to 20-year in situ warming in an Icelandic heathland. We evaluated the effect of warming and warming-induced shrub expansion on the moss bacterial community composition and diversity, nifH gene abundance and nitrogen-fixation rates. C_LIO_LIWarming changed both the total and the potentially active bacterial community structure, while litter abundance only affected the total bacterial community structure. The relative abundance of Proteobacteria increased, while the relative abundance of Cyanobacteria and Acidobacteria decreased. NifH gene abundance and nitrogen-fixation rates were negatively affected by litter and Betula nana abundance, respectively. We also found shifts in the potentially nitrogen-fixing community, with Nostoc decreasing and non-cyanobacterial diazotrophs increasing in relative abundance. Our data suggests that the moss microbial community including the potentially nitrogen-fixing taxa is sensitive to future warming. C_LIO_LISynthesis. Long-term warming led to a shift in moss-associated bacterial community composition, while the abundance of nitrogen-fixing bacteria and nitrogen-fixation rates were negatively affected by increased litter and Betula nana abundance respectively. Warming and increased shrub abundance as a result of warming can affect moss-associated bacterial communities and nitrogen fixation rates in tundra ecosystems. C_LI

microbiology↗

bioRxiv2019

Energetic and Environmental Constraints on the Community Structure of Benthic Microbial Mats in Lake Fryxell, Antarctica

Ecological communities are commonly thought to be controlled by the dynamics of energy flow through environments. Two of the most important energetic constraints on all communities are photosynthetically active radiation (PAR) and oxygen concentration ([O2]). Microbial mats growing on the bottom of Lake Fryxell, Antarctica, span environmental gradients in PAR and [O2], which we used to test the extent to which each controls community structure. Metagenomic analyses showed variation in the diversity and relative abundances of Archaea, Bacteria, and Eukaryotes across three [O2] and PAR conditions. Where [O2] saturated the mats or was absent from the overlying water, PAR structured the community. Where [O2] varied within mats, microbial communities changed across covarying PAR and [O2] gradients. Diversity negatively correlated with [O2] and PAR through mat layers in each habitat suggesting that, on the millimeter-scale, communities are structured by the optimization of energy use. In contrast, [O2] positively correlated with diversity and affected the distribution of dominant populations across the three habitats, suggesting that meter-scale diversity is structured by energy availability. The benthic microbial communities in Lake Fryxell are thus structured by energy flow in a scale-dependent manner.

microbiology↗