Biology subjects

Eckhardt, S.

Publications and source records attributed to Eckhardt, S..

4 recordsLinked to original sources

bioRxiv2026

Virus-host interactions on volcanic ash from Mount Etna

Volcanic ash represents an extreme and dynamic habitat, yet it hosts diverse microbial communities with largely unexplored viral diversity. This study investigated bacterial and viral populations in volcanic ash from Mount Etna (Italy) collected during the eruption, focusing on microbial novelty, activity, and virus-host interactions. Taxonomic profiling revealed that Pseudomonas and Telluria were the dominant bacterial genera, both frequently detected in airborne environments. In contrast, enrichment cultures with volcanic ash were dominated by spore-forming members of the phylum Bacillota, highlighting their resilience under harsh conditions. Metagenomic analysis recovered 19 high-quality metagenome-assembled genomes, including four previously undescribed bacterial species. Replication rate estimates showed that certain taxa were metabolically active, particularly at one sampling site. The presence of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) systems with spacers matching viral sequences suggested viral predation pressure on volcanic ash. A total of 1139 viral operational taxonomic units (vOTUs) were identified, of only around half (660 vOTUs) showed similarities to known phages, underscoring the presence of novel viruses. Shared vOTUs across sites revealed the presence of both a core virome and site-specific viral populations. Virus-host predictions indicated frequent interactions with hosts from multiple Gammaproteobacterial genera. Additionally, a 336 kb jumbo phage genome exhibited extensive metabolic capabilities and genetic autonomy. Experimental work identified a unique lytic Bacillus-infecting phage ("Phoenix") with limited propagation capacity. Furthermore, prophage induction experiments revealed active, morphologically diverse temperate phages across multiple bacterial host strains. Overall, these findings highlight volcanic ash as a reservoir of microbial and viral diversity, shaped by environmental extremes and dynamic ecological interactions. HighlightsMetagenomic and cultivation experiments were used to study viruses on volcanic ash Novelty of viral and bacterial species was detected Viral-bacterial interactions in metagenomes from volcanic ash were detected Cultivatable bacteria were mainly spore-forming Bacilli species and harbored inducible prophages

microbiology↗

bioRxiv2026

Virus-host interactions and viral population dynamics across atmospheric cloud events

BackgroundCloud water harbors diverse microbial communities despite its extreme oligotrophic conditions. However, the ecological and evolutionary dynamics of viruses in these transient atmospheric habitats remain poorly understood. Clouds have traditionally been regarded primarily as passive carriers of microorganisms rather than as active ecological environments supporting microbial interactions. In this study, cloud water was sampled at Mount Verde, Cape Verde Islands (744 m a.s.l.). We performed metagenomic analyses of iron-flocculated cloud water alongside genome analyses of a bacterial isolate and metagenome-assembled genomes using established bioinformatic approaches. Viral diversity, virus-host interactions, metabolic functions, genetic adaptations, and viral population dynamics across cloud events were investigated. In addition, UV-B resistance experiments were conducted for a novel cloud-water isolate. ResultsWe isolated 24 cloud water bacteria, including four novel species lineages, and recovered 62 high-quality metagenome-assembled genomes, including 10 novel species lineages. We identified 458 viral operational taxonomic units and 237 virus-host linkages across diverse prokaryotic hosts, revealing active viral predation across diverse bacterial taxa. In addition, CRISPR spacer matches from isolates of novel bacterial lineages such as Deinococcus nubigenus MPC36 were found. Viruses carried genes involved in host adaptation to environmental stressors, including cold-shock response, UV radiation resistance, and osmotic stress. In addition, viral populations exhibited SNP-level microdiversity and shifts in single-nucleotide variant composition across temporally proximate cloud events, indicating rapid population turnover. Experimental characterization of the cloud isolate Curtobacterium nubigenum MPC39 further revealed pronounced resistance to UV-B radiation and the presence of an inducible prophage, Curtobacterium phage vB_CnuS_Cirrus1 assigned to the new viral family Nebulaviridae, which could be validated in transmission electron microscopy. Reconstructed genomes from cloud-associated bacteria encoded carbon monoxide dehydrogenase genes and UV resistance genes, suggesting trace gas metabolism and enhanced UV protection as survival strategies in oligotrophic cloud droplets. In silico replication rates estimated using iRep were consistent with active bacterial replication at the time of sampling. ConclusionsTogether, these findings demonstrate that clouds are not merely passive carriers of microorganisms, but dynamic atmospheric ecosystems in which virus-host interactions shape microbial diversity and contribute to microbial turnover, atmospheric dispersal, and cloud-water biogeochemistry.

microbiology↗

bioRxiv2024

Tree growth is better explained by absorptive fine roots than transport fine roots

O_LIQuantifying plant trait variation yields insights into trade-offs inherent in the ecological strategies of plants and is the basis for a trait-based prediction of plant performance and ecosystem functioning. Although the interest in root traits has increased in recent years, we still have limited knowledge of i) whether functionally different fine roots--absorptive versus transport roots--have similar trait coordination and ii) how they help to explain plant performance, such as growth. C_LIO_LIWe measured traits of 25 European broadleaved tree species growing in a research arboretum to study i) the coordination of root traits within absorptive and transport fine roots and ii) the degree of trait-tree growth relationships. To do so, we combined a suite of morphological (root diameter, specific root length and root tissue density) and anatomical (cortex to stele ratio and arbuscular mycorrhizal colonization rate) traits for each of the absorptive and transport roots and also leaf traits (leaf mass per area, dry matter content and toughness). C_LIO_LIDespite remarkable differences in average trait values between absorptive and transport roots, our study shows that trait coordination within absorptive and transport roots is relatively equivalent. Our results also show that, for the traits we studied, tree growth is better explained by absorptive root traits than by transport root traits and is higher in species with a thinner root diameter. This suggests that variation primarily in absorptive roots affects the uptake of soil-based resources like nutrients and water and directly influences tree growth. C_LIO_LIThe significant relationship between absorptive roots and tree growth and the lack of such a relationship for transport roots highlights that roots mostly involved with resource absorption are more important in explaining tree growth than roots involved in transport. C_LI

ecology↗

bioRxiv2022

Neighbourhood species richness and drought-tolerance traits modulate tree growth and δ13C responses to drought

O_LIMixed-species forests are promoted as a forest management strategy for climate change adaptation, but whether they are more resistant to drought than monospecific forests remains contested. Particularly, the trait-based mechanisms driving the role of tree diversity under drought remain elusive. C_LIO_LIUsing tree cores from a large-scale biodiversity experiment, we investigated tree growth and physiological stress responses (i.e. increase in wood carbon isotopic ratio; {delta}13C) to changes in climate-induced water availability (wet to dry years) along gradients in neighbourhood tree species richness and drought-tolerance traits. We hypothesized that neighbourhood species richness increases growth and decreases {delta}13C and that these relationships are modulated by the abiotic (i.e. climatic conditions) and the biotic context. We characterized the biotic context using drought-tolerance traits of focal trees and their neighbours. These traits are related to cavitation resistance vs resource acquisition and stomatal control. C_LIO_LITree growth increased with neighbourhood species richness. However, we did not observe a universal relief of water stress in species-rich neighbourhoods. Neighbourhood species richness effects on growth and {delta}13C did not strengthen from wet to dry years. Instead, richness-growth and richness-{delta}13C relationships were modulated by climatic conditions and the traits of trees and their neighbours. At either end of each drought-tolerance gradient, species responded in opposing directions during drought and non-drought years. C_LIO_LIWe show that species drought-tolerance traits can explain the strength and nature of biodiversity-ecosystem functioning relationships in experimental tree communities experiencing drought. Mixing tree species can increase growth but may not universally relieve drought stress. C_LI One-sentence summaryThe drought-tolerance traits of trees and their neighbours determine biodiversity-ecosystem functioning relationships in experimental tree communities.

ecology↗