Biology subjects

Juottonen, H.

Publications and source records attributed to Juottonen, H..

4 recordsLinked to original sources

bioRxiv2025

Aridity drives global convergence of desert microbiomes and biogeochemical activities

Deserts cover a third of the worlds surface, supporting unique biomes and ecosystem services. Yet, we lack a comprehensive assessment of what defines and drives the microbial communities that dominate life in these regions. Here, we conducted a standardized field survey in contrasting cold, hot, and polar deserts across the seven continents, and observed geographically distant deserts share similar structure, function, and activities. Desert communities are dominated by genomically streamlined Actinobacteriota and Chloroflexota, and compared with non-desert soils, are significantly enriched with stress tolerance genes, mobile genetic elements, and antiviral strategies, revealing previously unknown ecological and evolutionary dynamics. Metabolically, these communities exhibit reduced capacity for carbohydrate and protein degradation, and instead are enriched for chemosynthetic carbon fixation, continuous energy harvesting using atmospheric trace gases and sunlight, and energy reserve biosynthesis. All sampled soils mediated respiration, trace gas oxidation, and carbon fixation, with detectable activity even in hyper-arid Atacama and Antarctic soils at the margins of life. Driver analyses identified aridity as the primary overriding driver of the microbial communities and biogeochemical activities. Collectively, these findings suggest that aridity selects for metabolically self-sufficient taxa capable of continuously meeting energy and carbon needs independently of vegetation-derived inputs, while enduring physicochemical stressors and potentially elevated viral pressure. These new insights are integral to forecast the future of soils amid increasing desertification. Significance statementDesert soils occupy a vast and expanding portion of Earth, yet what defines and governs their dominant microbial life remains incompletely defined. By assessing the composition, capabilities, and activities of microbial communities across deserts on all seven continents, we identify unifying signatures of life under extreme water limitation. We show microbial communities are highly self-sufficient, capable of acquiring energy and carbon even where plant inputs are minimal. This planetary-scale understanding of the desert microbiome has important ramifications for forecasting potential shifts of microbial communities and the services they provide as desertification intensifies.

microbiology↗

bioRxiv2024

Low determinism in pelagic fungal community assembly across climate zones in Scandinavian lakes

In lakes, fungi play pivotal roles in biogeochemical processes, particularly in the decomposition of organic matter. However, these organisms have been historically underrepresented and taxonomically unresolved in previous research. In this study, we employ high-resolution sequencing to delve into the fungal diversity within two distinct Scandinavian lake datasets spanning a vast latitudinal gradient, diverse climatic zones ranging from nemoral to arctic, and a wide spectrum of nutrient conditions. Utilizing eukaryotic primers, we reveal that fungi contribute, on average, 2.07% in the Norwegian and 5.4% in the Swedish sequencing dataset, with remarkable spikes of up to 55% in forested lakes. Fungal-specific sequencing identified the prevalence of several fungal phyla, including Ascomycota, Rozellomycota, Basidiomycota, Chytridiomycota, Aphelidiomycota, and Mortierellomycota. Notably, our research uncovers a striking degree of variability in fungal communities across the studied lakes, defying correlations with measured environmental factors or geographic distance. Null model analyses suggest that deterministic processes do not consistently override the influence of ecological drift in shaping these biogeographic patterns. However, signals for dispersal limitations and mass effects could be detected. These findings challenge conventional paradigms of eukaryotic communities being strongly guided by deterministic processes and underscore the complexity of fungal community assembly processes across climate zones.

microbiology↗

bioRxiv2022

Host's genetic background determines the outcome of reciprocal faecal transplantation on life-history traits and microbiome composition

BackgroundMicrobes play a role in fundamental ecological, chemical, and physiological processes of their host. Host life-history traits from defence to growth are therefore determined not only by abiotic environment and genotype but also by microbiota composition. However, the relative importance and interactive effects of these factors may vary between organisms. Such connections remain particularly elusive in Lepidoptera, which have been argued to lack a permanent microbiome and have microbiota primarily determined by their diet and environment. We tested the microbiome specificity and its influence on life-history traits of two colour genotypes of the wood tiger moth (Arctia plantaginis) that differ in several traits, including growth. All individuals were grown in the laboratory for several generations with standardised conditions. We analysed the bacterial community of the genotypes before and after a reciprocal frass (i.e., larval faeces) transplantation and followed growth rate, pupal mass, and the production of defensive secretion. ResultsAfter transplantation, the fast-growing genotype grew at a significantly slower rate compared to the controls, but the slow-growing genotype did not change its growth rate. The frass transplant also increased the volume of defensive secretions in the fast-growing genotype but did not affect pupal mass. Overall, the fast-growing genotype appeared more susceptible to the transplantation than the slow-growing genotype. Microbiome differences between the genotypes strongly suggest genotype-based selective filtering of bacteria from the diet and environment. A novel cluster of insect-associated Erysipelotrichaceae was exclusive to the fast-growing genotype, and specific Enterococcaceae were characteristic to the slow-growing genotype. These Enterococcaceae became more prevalent in the fast-growing genotype after the transplant, which suggests that the slower growth rate was potentially related to their presence. ConclusionsWe show that some genotype-specific life-history traits in a lepidopteran host can be reversed by a reciprocal frass transplantation. The results indicate that genotype-specific selective filtering can fine-tune the bacterial community at specific life stages, particularly the larval gut, even against a background of a highly variable community with stochastic assembly. Altogether, our findings suggest that the genotype of the host can influence its susceptibility to be colonized by microbiota with impact on key life-history traits.

evolutionary biology↗

bioRxiv2019

Cryptogams signify key transition of bacteria and fungi in Arctic sand dune succession

O_LIPrimary succession models focus on aboveground vascular plants. However, the prevalence of mosses and lichens, i.e. cryptogams, suggests they play a role in soil successions. Here, we explore whether effects of cryptogams on belowground microbes can facilitate progressive shifts in sand dune succession. C_LIO_LIWe linked aboveground vegetation, belowground bacterial and fungal community, and soil chemistry in six successional stages in Arctic inland sand dunes: bare sand, grass, moss, lichen, ericoid heath and mountain birch forest. C_LIO_LICompared to the bare sand and grass stages, microbial biomass and the proportion of fungi increased in the moss stage, and later stage microbial groups appeared despite the absence of their host plants. The microbial communities of the lichen stage resembled the communities in the vascular plant stages. Bacterial community correlated better with soil chemistry than with vegetation, whereas the correlation of fungi with vegetation increased with vascular vegetation. C_LIO_LIDistinct bacterial and fungal patterns of biomass, richness, and plant-microbe interaction showed that the aboveground vegetation change structured the bacterial and fungal community differently. The nonalignment of aboveground vs. belowground changes suggests that cryptogams can drive succession towards vascular plant dominance through microbially mediated facilitation in eroded Arctic soil. C_LI

ecology↗