Biology subjects

Haberkorn, C.

Publications and source records attributed to Haberkorn, C..

9 recordsLinked to original sources

bioRxiv2026

Strong habitat-associated differentiation of microbial communities across a fine-scale land-water interface

Microbial communities can remain strongly differentiated across environmental boundaries despite their potential for widespread dispersal. However, the extent to which habitat differences structure microbial communities at fine spatial scales remains poorly understood. Here, we investigated bacterial and fungal communities across a 350-m land-water interface in Lake Vanern, Sweden, including mainland soil, two small terrestrial islands and lake water. Using 16S and ITS amplicon sequencing, we compared microbial diversity and community composition across habitats and with increasing distance from the shoreline. Both bacterial and fungal communities showed pronounced habitat-associated differentiation, with the strongest contrasts between terrestrial and aquatic samples. Despite being surrounded by lake water, island communities were compositionally more similar to mainland soil communities, suggesting that geographic proximity alone does not necessarily lead to microbial community homogenization. Fungal, but not bacterial community composition varied significantly with shoreline position within both terrestrial and aquatic habitats, indicating contrasting spatial patterns between the two groups. Fungal genera also showed greater taxonomic overlap between terrestrial and aquatic habitats than bacterial genera, although overall community composition remained distinct. Taxonomically inferred functional profiles and ecological guilds further reflected habitat-associated differences. Together, our findings reveal strong microbial community differentiation across a fine-scale land-water interface and highlight how habitat identity and spatial context are associated with distinct patterns of bacterial and fungal community assembly.

microbiology↗

bioRxiv2026

Mitochondrial inheritance as an important parameter for the rational design of synthetic yeast polyploids

Synthetic allopolyploidization is a powerful strategy for generating strains with novel industrially relevant traits. During the design of select, hybridize, evolved and learn cycle, the mitochondrial inheritance is considered neutral and most studies overcome their phenotypic impact. Here, we generated 168 synthetic allotetraploid strains representing all pairwise parental combinations of eight wild Saccharomyces species, and systematically controlled mitochondrial inheritance in these crosses. These allopolyploids were phenotyped across 31 environmental conditions relevant to biotechnology. In ~50% of all condition-strain combinations conditions, allotetraploids exhibited mid-parent heterosis. In approximately 25% of conditions, we found crosses with hybrid vigor, particularly in combinations involving Saccharomyces arboricola x Saccharomyces mikatae . However, allotetraploids were highly unstable and rapidly sporulated. Our analyses revealed that environmental conditions accounted for the largest effects, follow by its interaction with mitotype. However, mitotype alone showed small effects but significantly affected 42% of the tested conditions, underscoring the importance of mitochondrial inheritance as a key determinant of allopolyploid performance. These findings demonstrate that mitochondrial inheritance is a key, environment-dependent determinant of allopolyploid fitness and should be considered alongside nuclear genome composition in the rational design of industrial allopolyploid strains

microbiology↗

bioRxiv2026

Repeated heat waves trigger divergent transcriptional responses in cold- and warm-adapted yeast species

Extreme climatic events such as heat waves pose major challenges to species survival and have profound impacts on evolutionary processes. Plasticity is thought to buffer organismal stress, yet the molecular mechanisms underlying plastic responses remain poorly understood. In particular, the role of transcriptional plasticity and stress memory in responding to repeated stress events remains unresolved. Here, we experimentally exposed clonal populations of eight divergent Saccharomyces yeast species with different thermal tolerances to repeated heat waves. We compared their phenotypic and transcriptomic profiles after a few generations of mitotic growth, reflecting transcriptional changes. Warm-adapted species maintained higher growth than cold-adapted species across heat wave exposures. Thermo-generalist species showed intermediate outcomes with one species improving growth across repeated heat waves. To interpret transcriptomic results, we used a conceptual framework separating no-memory (gene expression independent from prior exposure) from memory-associated responses (expression modulated by prior exposure). No-memory responses showed conserved transcriptomic signatures of proteostasis induction, and reduced expression of ribosome biogenesis and translation upon repeated heat waves. Memory-associated responses were more rare and highly species-specific, showing opposite patterns of (de)sensitization in ribosomal and translational pathways in species at the two extremes of thermal tolerance. Together, our results show that thermal resilience can arise through alternative transcriptional changes and suggests that warm- and cold-temperature specialists adopt divergent gene regulatory strategies upon repeated heat waves. With climate change projections indicating more frequent and intense heat waves, understanding plastic responses across species with ecologically and genetically different backgrounds is crucial.

evolutionary biology↗

bioRxiv2025

Divergent ecological selection causes partial reproductive isolation and vast genomic instability in yeast

Populations evolving independently in divergent environments accumulate genetic differences and potentially evolve reproductive isolation as a by-product of divergence. The speed and mechanisms underlying this process are difficult to investigate because we rarely get the opportunity to witness them in natural settings, and histories of selection and gene flow between populations are often unknown. Here, we experimentally evolved yeast for 1000 generations of evolution in both divergent and parallel environments. At regular time points during experimental evolution, we made crosses between parallel- and divergent-evolving populations to measure postzygotic reproductive isolation (gamete viability). We used whole genome population sequencing to determine the mutational load, the number and types of structural variation, and other genomic features of the parent, F1, and F2 intraspecific hybrids. We found evidence for large scale phenotypic and genome-wide differentiation in response to divergent laboratory selection. Divergent-selected populations produced hybrids with reduced gamete viability - a classic signature of postzygotic reproductive isolation in the form of hybrid breakdown. Parallel-selected populations on the other hand remained more reproductively compatible (with exceptions). We found that F2 hybrid genomes contained vast genomic instability, i.e., new structural variants (especially insertions, deletions, and interchromosomal translocations) that were not observed in parent and F1 genomes, which is likely a result of chromosome missegregation and recombination errors in hybrid meiosis. Our results provide phenotypic and genomic evidence that partial reproductive isolation evolved due to adaptation to divergent environments, consistent with predictions of ecological speciation theory.

evolutionary biology↗

bioRxiv2025

Fermentative yeast diversity at the northern range limit of their oak tree hosts

Fermentative yeasts play important roles in both ecological and industrial processes but their distribution and abundance in natural environments is not well understood. We investigated the diversity of yeast species associated with oak trees (Quercus spp.) in the northern range limit of oak in Sweden, and identified climatic and ecological conditions governing their distribution. We isolated yeasts from oak bark collected from 28 forests and identified them to the species level using metabarcoding. Most communities were dominated by species in the Saccharomycetaceae family, especially by species of Saccharomyces, Kluyveromyces, and Pichia. Each of these genera showed a distinct latitudinal and longitudinal distribution, and both temperature and precipitation metrics predicted significant variation in their abundance. Consistent with this, laboratory assays revealed significant effects of temperature on the growth of strains collected from different longitudes and latitudes. We further found that older trees harbour more diverse and more balanced microbial communities with more evenly distributed species abundances, and that communities across trees were more similar when sharing a common dominant genus. This work provides a baseline for future studies on the impact of climate change on the microbial biodiversity of temperate forests in northern latitudes, and contributes to a growing collection of fermentative yeasts isolated from the wild with potential for biotechnological applications.

microbiology↗

bioRxiv2024

A genomic duplication spanning multiple P450s contributes to insecticide resistance in the dengue mosquito Aedes aegypti

Resistance of mosquitoes to insecticides is one example of rapid adaptation to anthropogenic selection pressures having a strong impact on human health and activities. Target-site modification and increased insecticide detoxification are the two main mechanisms underlying insecticide resistance in mosquitoes. While target-sites mutations are well characterised and often used to track resistance in the field, the genomic events associated with insecticide detoxification remain partially characterised. Recent studies evidenced the key role of gene duplications in the over-expression of detoxification enzymes and their potential use to track metabolic resistance alleles in the field. However, such genomic events remain difficult to characterise due to their complex genomic architecture and their co-occurrence with other resistance alleles. In this concern, the present work investigated the role of a large genomic duplication affecting a cluster of detoxification enzymes in conferring resistance to the pyrethroid insecticide deltamethrin in the mosquito Aedes aegypti. Two isofemale lines originating from French Guiana and being deprived from major target-site mutations showed distinct insecticide resistance levels. Combining RNA-seq and whole genome pool-seq identified a 220 Kb genomic duplication enhancing the expression of multiple contiguous cytochrome P450s in the resistant line. The genomic architecture of the duplicated loci was elucidated through long read sequencing, evidencing its transposon-mediated evolutionary origin. The involvement of this P450 duplication in deltamethrin survival was supported by a significant phenotypic response to the P450 inhibitor piperonyl butoxide together with genotype-phenotype association and RNA interference. Experimental evolution suggested that this P450 duplication is associated with a significant fitness cost, potentially affecting its adaptive value in presence of other resistance alleles. Overall, this study supports the importance of genomic duplications affecting detoxification enzymes in the rapid adaptation of mosquitoes to insecticides. Deciphering their genomic architecture provides new insights into the evolutionary processes underlying such rapid adaptation. Such findings provide new tools for the surveillance and management of resistance in the field.

evolutionary biology↗

bioRxiv2024

Transcriptomic response to pyrethroid treatment in closely related bed bug strains varying in resistance

The common bed bug, Cimex lectularius, is one of the main human parasites. The world-wide resurgence of this pest is mainly due to globalization, and the spread of insecticide resistance. A few studies have compared the transcriptomes of susceptible and resistant strains. However, these studies usually relied on strains originating fromdistant locations, possibly explaining their extended candidate gene lists. Here, we compared the transcriptomes of two strains originating from the same location and showing low overall genetic differentiation (FST =0.018) but varying in their susceptibility to pyrethroids, before and after insecticide exposure. In sharp contrast with previous studies, only 24 genes showing constitutive differential expression between the strainswere identified. Interestingly, most of the genes with increased expression in the resistant strain encoded cuticular proteins. However, those changes were not associated with significant difference in cuticular thickness, suggesting that they might be involved in qualitative changes in the cuticle. In contrast, insecticide exposure induced the expression of a multitude of genes, mostly involved in detoxification. Finally, our set of transcriptome candidate loci showed little overlap with a set of loci strongly genetically differentiated in a previous study using the same strains. Several hypothesis explaining this discrepancy are discussed.

evolutionary biology↗

bioRxiv2023

A major 6 Mb superlocus is involved in pyrethroid resistance in the common bed bug Cimex lectularius

In the last few years, the bed bug Cimex lectularius has been an increasing problem world-wide, mainly due to the development of insecticide resistance to pyrethroids. The characterization of resistance alleles is a prerequisite to improve surveillance and resistance management. To identify genomic variants associated with pyrethroid resistance in Cimex lectularius, we compared the genetic composition of two recent and resistant populations with that of two ancientsusceptible strains using a genome-wide pool-seq design. We identified a large 6 Mb "superlocus" showing particularly high genetic differentiation and association with the resistance phenotype. This superlocus contained several clustered resistance genes, and was also characterized by a high density of structural variants (inversions, duplications). The possibility that this superlocus constitutes a resistance "supergene" that evolved after the clustering of alleles adapted to insecticide and after reduction in recombination is discussed.

evolutionary biology↗

bioRxiv2020

A novel assay for tracking carboxylesterase gene amplifications conferring organophosphate resistance in the mosquito Aedes aegypti: from experimental evolution to field application

By altering gene expression and creating paralogs, genomic amplifications represent a key component of short-term adaptive processes. In insects, the use of insecticides can select gene amplifications causing an increased expression of detoxification enzymes, supporting the usefulness of these DNA markers for monitoring the dynamics of resistance alleles in the field. In this context, the present study aims to characterise a genomic amplification event associated with resistance to organophosphate insecticides in the mosquito Aedes aegypti and to develop a molecular assay to monitor the associated resistance alleles in the field. An experimental evolution experiment using a composite population from Laos supported the association between the over-transcription of multiple contiguous carboxylesterase genes on chromosome 2 and resistance to multiple organophosphate insecticides. Combining whole genome sequencing and qPCR on specific genes confirmed the presence of a ~100 Kb amplification spanning at least five carboxylesterase genes at this locus with the co-existence of multiple structural duplication haplotypes. Field data confirmed their circulation in South-East Asia and revealed high copy number polymorphism among and within populations suggesting a trade-off between this resistance mechanism and associated fitness costs. A dual-colour multiplex TaqMan assay allowing the rapid detection and copy number quantification of this amplification event in Ae. aegypti was developed and validated on field populations. The routine use of this novel assay will improve the tracking of resistance alleles in this major arbovirus vector.

evolutionary biology↗