Biology subjects

Dunn, R. R.

Publications and source records attributed to Dunn, R. R..

10 recordsLinked to original sources

bioRxiv2026

Insights from sourdough redefine the domestication landscape of baker's yeast

While the domestication of plants and animals is widely recognized for its role in the rise of human civilization, humans have also cultivated microbes over millennia to produce food and beverages. One microbe in particular, Saccharomyces cerevisiae, is associated with a wide variety of human-fermentation environments, including wine, beer, and notably bread, such that it is often referred to as "bakers yeast." To better illuminate the domestication history of baking associated yeast, we isolated 38 Saccharomyces cerevisiae strains from sourdough starters donated by bakers throughout North America and compared them to thousands of S. cerevisiae isolates from a variety of wild and human-fermentation environments. We identified 6 major clades with two primary domestication hubs, Mediterranean liquid-state fermentation and Asian solid-state fermentation, diverging across Eurasia that gave rise to human-associated lineages. Population genomic analyses demonstrate that S. cerevisiae strains found in sourdough starters are genetically distinct from commercial baking strains and do not come from the surrounding wild environment. Our results show that sourdough yeast strains are closely related to each other and have shared ancestry with strains isolated from various Asian solid state grain fermentations such Japanese sake, Asian rice wines, Chinese distilled spirits (baijiu), and Chinese steamed bread (mantou). We found evidence of significant admixture throughout S. cerevisiae populations, including baking-associated lineages, likely facilitated by human activity. Pangenome gene content largely captures S. cerevisiae traditional genomic sequence-based population structure and reflects human cultural practices, with differences in gene content and copy number between baking associated strains and other groups. Overall, we show that many generalized hallmarks of domestication, such as genome contraction, loss of genetic diversity, and lack of niche expansion, are not universal features of S. cerevisiae domestication, and that baking-associated yeasts have a complex evolutionary history heavily shaped by human culture.

evolutionary biology↗

bioRxiv2025

Does Fermentation Enhance Beverage Safety? Kombucha's Resistance to Microbial Invasion Suggests a Protective Role

Does fermentation enhance the safety of beverages? This study investigates kombuchas resilience to microbial invasion from human hands. Kombucha, an ancient fermented tea, relies on a biofilm known as a symbiotic community of bacteria and yeast (SCOBY) and a starter culture to ferment sweet tea, producing various metabolites including gluconic acid, acetic acid, ethanol, and carbon dioxide. While fermented foods have been historically associated with potential health benefits, direct evidence comparing the prevalence of human pathogens in fermented versus non-fermented beverages has been lacking. To address this, we conducted a citizen science experiment at Arizona State University, introducing swabs from peoples palms into both kombucha and a sweet tea control. Over 30 days, we monitored the bacterial and fungal composition using 16S and ITS rRNA sequencing. Our findings reveal that kombucha maintained a relatively stable microbial profile and physical appearance, with a typical SCOBY biofilm developing. In stark contrast, the sweet tea experienced a dramatic change in microbial composition and was visibly compromised by rapidly growing microorganisms. Importantly, this suggests that the complex microbial ecosystem of kombucha can limit the growth of foreign microbes introduced from human hands. Given that human pathogens were absent from the kombucha while present in the tea samples, our results indicate that the antimicrobial properties of fermentation byproducts and the physical barrier of the SCOBY may contribute to this resilience. Further research is warranted to fully elucidate the mechanisms underlying kombuchas resistance to microbial invasion.

microbiology↗

bioRxiv2025

Evolutionary genomics reveals plant origins of acetic acid bacteria in fermented food

Humans have historically relied on acetic acid bacteria (AAB) for food fermentation, yet their origins must trace back to free-living species outside of human environments. In nature, plants, fruit flies, and social insects host AAB. However, the evolutionary transitions of AAB from symbiotic hosts to fermented foods remain ambiguous. Here, we conduct a comprehensive phylogenomic analysis of 570 publicly available AAB genomes. We find that the [~]170My evolutionary history of this group is concordant with the rise of angiosperms, corbiculate bees, and the consequential accelerated availability of environmental carbohydrates. Unlike other ferment-associated microbes, ferment-associated AAB have exclusively evolved from clades inhabiting flowers and fruits, but not insect hosts. Genomic features are similar in plant- and ferment-associated AAB, yet markers of early adaptation to ferments are also present. Conversely, social insect-associated AAB have reduced genome sizes, which may have limited their functional capability to disperse into ferments. Plant- and ferment-associated AAB coincide in the ability to metabolise diverse plant carbohydrates, though both have adapted to produce habitat-specific carbohydrate-active enzymes. In contrast, metabolic capacity is reduced in social insect-associated AAB. By tracing the phylogenomics of this clade, we understand how evolution forged AAB capable of performing metabolic work for humans, shaping the history and potential futures of fermentation.

evolutionary biology↗

bioRxiv2024

Making yogurt with the ant holobiont uncovers bacteria, acids, and enzymes for food fermentation

Milk fermentation has a rich history in which food culture, the environment, and microbes intersect. However, the biocultural origins of fermentation practices and microbes have largely been replaced by industrial processes. Here, we consider a historical fermentation originating from Turkey and Bulgaria - ant yogurt. We revisit the traditional practices and modern gastronomic applications that use red wood ants (Formica rufa group) to initiate milk fermentation. Subsequently, we characterize the ants and experimental ant-derived yogurts. We uncover that the ant holobiont, which consists of the ants and their microbes, contributes key acids and enzymes to fermentation. Metabarcoding and culturing revealed that lactic and acetic acid bacteria, including species related to conventional sourdough, originate from the live ants and proliferate in the milk. The ants and bacteria consequently introduce formic, lactic, and acetic acid, advantageous for yogurt acidification and coagulation. Last, proteases with the potential to act on casein may alter yogurt texture and are produced by the ants and bacteria. The ant holobiont thus catalyses fermentation akin to the microbial consortia in other ferments. Our findings highlight the value of integrating traditional, gastronomic, and biological frameworks to uncover the origins and applications of microbes for fermented foods.

microbiology↗

bioRxiv2022

Quantifying the Human Cost of Global Warming

The costs of climate change are often estimated in monetary terms1,2 but this raises ethical issues3. Here we express them in terms of numbers of people left outside the human climate niche4 - defined as the historically highly-conserved distribution of relative human population density with respect to mean annual temperature (MAT). We show that climate change has already put [~]8% of people (>500 million) outside this niche. By end-of-century (2080-2100), current policies leading to around 2.7 {degrees}C global warming5-9 could leave one third (21-42% or 2-4 billion) of a future 9.5 billion population outside the niche. Limiting global warming to 1.5 {degrees}C could halve this exposure, reducing it by [~]1.5 billion people. For the two countries with the most people affected - India and Nigeria - reducing global warming from 2.7 to 1.5 {degrees}C results in a >6-fold decrease in the population exposed to unprecedented temperatures, MAT [≥]29 {degrees}C. The lifetime emissions of [~]3.5 global average citizens today (or [~]1.2 average US citizens) expose 1 future person to MAT [≥]29 {degrees}C by end-of-century. That person comes from a place where emissions today are around half of the global average. These results highlight the need for more decisive policy action to limit the human costs and inequities of climate change.

ecology↗

bioRxiv2021

Understanding the Evolution of Nutritive Taste in Animals: Insights from Biological Stoichiometry and Nutritional Geometry

A major conceptual gap in taste biology is the lack of a general framework for understanding the evolution of different taste modalities among animal species. We turn to two complementary nutritional frameworks, biological stoichiometry theory and nutritional geometry, to develop hypotheses for the evolution of different taste modalities in animals. We describe how the attractive tastes of Na, Ca, P, N and C containing compounds are consistent with principles of both frameworks based on their shared focus on nutritional imbalances and consumer homeostasis. Specifically, we suggest that the evolution of multiple nutritive taste modalities can be predicted by identifying individual elements that are typically more concentrated in the tissues of animals than plants. Additionally, we discuss how consumer homeostasis can inform our understanding of why some taste compounds (i.e., Na, Ca and P salts) can be either attractive or aversive depending on concentration. We also discuss how these complementary frameworks can help to explain the phylogenetic distribution of different taste modalities and improve our understanding of the mechanisms that lead to loss of taste capabilities in some animal lineages. The ideas presented here will stimulate research that bridges the fields of evolutionary biology, sensory biology and ecology.

evolutionary biology↗

bioRxiv2020

Detecting flying insects using mega-nets and meta-barcoding

Insect diversity and abundance are increasingly reported as being under pressure. However, monitoring insects across space and time is challenging, due to their vast taxonomic and functional diversity. This study demonstrates how nets mounted on rooftops of cars (car nets) and DNA metabarcoding can be applied to sample flying insect diversity across a large spatial scale within a limited time period. During June 2018, 365 car net samples were collected by 151 volunteers during two daily time intervals on 218 routes in Denmark. Insect bulk samples were processed with a DNA metabarcoding protocol to estimate taxonomic composition, and the results were compared to known flying insect diversity and occurrence data. We detected 15 out of 19 flying insect orders present in Denmark. Diptera. Psocoptera and Thysanoptera were overrepresented, while Hymenoptera, Coleoptera, Lepidoptera, Trichoptera, Odonata, Neuroptera and Plecoptera were underrepresented, compared to Danish estimates. We detected 319 species not known for Denmark. Our results indicate that this method can assess the flying insect fauna to a wide extent, but may be, like other methods, biased towards certain insect orders. Furthermore, car net sampling and DNA metabarcoding can update species records for Denmark while preserving specimens for natural history collections.

ecology↗

bioRxiv2020

Contrasting impacts of urban and farmland cover on flying insect biomass

Recent studies report declines in biomass, abundance and diversity of terrestrial insect groups. While anthropogenic land use is one likely contributor to this decline, studies assessing land cover as a driver of insect dynamics are rare and mostly restricted in spatial scale and types of land cover. In this study, we used rooftop-mounted car nets in a citizen science project ( InsectMobile) to allow for large-scale geographic sampling of flying insects across Denmark and parts of Germany. Citizen scientists sampled insects along 278 10 km routes in urban, farmland and semi-natural (grassland, wetland and forest) landscapes in the summer of 2018. We assessed the importance of local to landscape-scale effects and land use intensity by relating insect biomass to land cover in buffers of 50, 250, 500 and 1000 m along the routes. We found a negative association of urban cover and a positive association of farmland on insect biomass at a landscape-scale (1000 m buffer) in both countries. In Denmark, we also found positive effects of all semi-natural land covers, i.e. grassland (largest at the landscape-scale, 1000 m), forests (largest at intermediate scales, 250 m), and wetlands (largest at the local-scale, 50 m). The negative association of insect biomass with urban land cover and positive association with farmland were not clearly modified by any variable associated with land use intensity. Our results show that land cover has an impact on flying insect biomass with the magnitude of this effect varying across spatial scales. Since we consistently found negative effects of urban land cover, our findings highlight the need for the conservation of semi-natural areas, such as wetlands, grasslands and forests, in Europe.

ecology↗

bioRxiv2020

Urban warming inverse contribution on risk of dengue transmission in the southeastern North America

O_LIPreventing diseases from becoming a problem where they are not is a common ground for disease ecology. The expectation for vector-borne diseases, especially those transmitted by mosquitos, is that warm and wet conditions favor vector traits increasing transmission potential. The advent of urbanization altering inner climate conditions hazards to increase mosquitos transmission potential on "disease-free" cooler areas as a consequence of a warming urban heat island (UHI) effect. C_LIO_LIWe assessed the realism of the anticipated dengue transmission potential into the southern United States in a causal pathway with the ongoing UHI effect, vectors spatial distribution patterns, and exogenous environment; We also measured the climatic niche similarity between both dengue vectors species. C_LIO_LIOur path model revealed that the UHI effect presents negative or no relation with dengue transmission potential. Instead, the surrounding non-urban temperature was rather suitable for the expected mosquitos transmission potential. C_LIO_LIBoth dengue vectors occurrence revealed to be more aggregated then expected by chance. These mosquitos density patterns were responsive to the warming effect of UHI-especially Aedes Aegypti-but not a reliable predictor for the anticipated dengue transmission potential pattern. The climatic niches of both vectors are not equivalent. Although currently highly overlapped, there is a wide space of their climatic niche still to be filled. C_LIO_LIPolicy implications. We highlight that the warming UHI effect on urban sites is not congruent with the expected suitability for dengue transmission. Instead, non-urban areas would be a better focus for dengue hazards into the southern United States. Our study also highlights the need for including low scale temperature on further mosquito-borne disease transmission models and track vectors niche filling under anthropogenic changes. C_LI

ecology↗

bioRxiv2018

American Gut: an Open Platform for Citizen-Science Microbiome Research

Although much work has linked the human microbiome to specific phenotypes and lifestyle variables, data from different projects have been challenging to integrate and the extent of microbial and molecular diversity in human stool remains unknown. Using standardized protocols from the Earth Microbiome Project and sample contributions from over 10,000 citizen-scientists, together with an open research network, we compare human microbiome specimens primarily from the USA, UK, and Australia to one another and to environmental samples. Our results show an unexpected range of beta-diversity in human stool microbiomes as compared to environmental samples, demonstrate the utility of procedures for removing the effects of overgrowth during room-temperature shipping for revealing phenotype correlations, uncover new molecules and kinds of molecular communities in the human stool metabolome, and examine emergent associations among the microbiome, metabolome, and the diversity of plants that are consumed (rather than relying on reductive categorical variables such as veganism, which have little or no explanatory power). We also demonstrate the utility of the living data resource and cross-cohort comparison to confirm existing associations between the microbiome and psychiatric illness, and to reveal the extent of microbiome change within one individual during surgery, providing a paradigm for open microbiome research and education.\n\nImportanceWe show that a citizen-science, self-selected cohort shipping samples through the mail at room temperature recaptures many known microbiome results from clinically collected cohorts and reveals new ones. Of particular interest is integrating n=1 study data with the population data, showing that the extent of microbiome change after events such as surgery can exceed differences between distinct environmental biomes, and the effect of diverse plants in the diet which we confirm with untargeted metabolomics on hundreds of samples.

microbiology↗