Chronic stress and captivity alter the cloacal microbiome of a wild songbird.

There are complex interactions between an organism's microbiome and its response to stressors, often referred to as the 'gut-brain axis'; however, the ecological relevance of this axis in wild animals remains poorly understood. Here, we used a chronic mild stress protocol to induce stress in wild-caught house sparrows (Passer domesticus), and compared microbial communities among stressed animals, those recovering from stress, captive controls (unstressed) and a group not brought into captivity. We assessed changes in microbial communities and abundance of shed microbes by culturing cloacal samples on multiple media to select for aerobic and anaerobic bacteria and fungi. We complemented this with cultivation-independent 16S and ITS rRNA gene amplification and sequencing, pairing these results with host physiological and immune metrics, including body mass change, relative spleen mass and plasma corticosterone concentrations. We found significant effects of stress and captivity on the house sparrow microbiomes, with stress leading to an increased relative abundance of endotoxin-producing bacteria - a possible mechanism for the hyperinflammatory response observed in captive avians. While we found evidence that the microbiome community partially recovers after stress cessation, animals may lose key taxa, and the abundance of endotoxin-producing bacteria persists. Our results suggest an overall link between chronic stress, host immune system and the microbiome, with the loss of potentially beneficial taxa (e.g. lactic acid bacteria), and an increase in endotoxin-producing bacteria due to stress and captivity. Ultimately, consideration of the host's microbiome may be useful when evaluating the impact of stressors on individual and population health.

Sugar-seeking insects as a source of diverse bread-making yeasts with enhanced attributes.

Insects represent a particularly interesting habitat in which to search for novel yeasts of value to industry. Insect-associated yeasts have the potential to have traits relevant to modern food and beverage production due to insect-yeast interactions, with such traits including diverse carbohydrate metabolisms, high sugar tolerance, and general stress tolerance. Here, we consider the potential value of insect-associated yeasts in the specific context of baking. We isolated 63 yeast strains from 13 species of hymenoptera from the United States, representing 37 yeast species from 14 genera. Screening for the ability to ferment maltose, a sugar important for bread production, resulted in the identification of 13 strains of Candida, Lachancea, and Pichia species. We assessed their ability to leaven dough. All strains produced baked loaves comparable to a commercial baking strain of Saccharomyces cerevisiae. The same 13 strains were also grown under various sugar and salt conditions relevant to osmotic challenges experienced in the manufacturing processes and the production of sweet dough. We show that many of these yeast strains, most notably strains of Lachancea species, grow at a similar or higher rate and population size as commercial baker's yeast. We additionally assessed the comparative phenotypes and genetics of insect-associated S. cerevisiae strains unable to ferment maltose and identified baking-relevant traits, including variations in the HOG1 signaling pathway and diverse carbohydrate metabolisms. Our results suggest that non-conventional yeasts have high potential for baking and, more generally, showcase the success of bioprospecting in insects for identifying yeasts relevant for industrial uses.

A review of sourdough starters: ecology, practices, and sensory quality with applications for baking and recommendations for future research.

The practice of sourdough bread-making is an ancient science that involves the development, maintenance, and use of a diverse and complex starter culture. The sourdough starter culture comes in many different forms and is used in bread-making at both artisanal and commercial scales, in countries all over the world. While there is ample scientific research related to sourdough, there is no standardized approach to using sourdough starters in science or the bread industry; and there are few recommendations on future directions for sourdough research. Our review highlights what is currently known about the microbial ecosystem of sourdough (including microbial succession within the starter culture), methods of maintaining sourdough (analogous to land management) on the path to bread production, and factors that influence the sensory qualities of the final baked product. We present new hypotheses for the successful management of sourdough starters and propose future directions for sourdough research and application to better support and engage the sourdough baking community.

Growsafe: A Chemical Method To Deactivate Cultivated Microorganisms Using Low-Cost Kitchen Supplies.

One limitation to engaging K-12 students and the public with microorganisms is the inability to cultivate and dispose of bacterial and fungal samples safely without expensive equipment or services. This barrier has been amplified with remote learning modalities and laboratory closures driven by safety precautions due to the COVID-19 pandemic. At-home lab kits are being used to bring hands-on experience in microorganism cultivation to students learning remotely, but these kits often fail to take into full consideration the safety aspects or the costs associated with microorganism disposal, limiting which experiments can be performed at home. Here, we outline a method that makes cultivating and deactivating microorganisms accessible to the public through low-cost and readily available equipment. This method reduces exposure to microorganisms by forgoing the need to open petri plates for chemical deactivation with sanitizing reagents. This technique may benefit remote K-12 and postsecondary students, students wishing to get hands-on microbiology research experience, and members of the public interested in cultivating microorganisms to contribute to citizen science efforts or for creative art applications.

The diversity and function of sourdough starter microbiomes.

Humans have relied on sourdough starter microbial communities to make leavened bread for thousands of years, but only a small fraction of global sourdough biodiversity has been characterized. Working with a community-scientist network of bread bakers, we determined the microbial diversity of 500 sourdough starters from four continents. In sharp contrast with widespread assumptions, we found little evidence for biogeographic patterns in starter communities. Strong co-occurrence patterns observed in situ and recreated in vitro demonstrate that microbial interactions shape sourdough community structure. Variation in dough rise rates and aromas were largely explained by acetic acid bacteria, a mostly overlooked group of sourdough microbes. Our study reveals the extent of microbial diversity in an ancient fermented food across diverse cultural and geographic backgrounds.

Sourdough bread is an ancient fermented food that has sustained humans around the world for thousands of years. It is made from a sourdough 'starter culture' which is maintained, portioned, and shared among bread bakers around the world. The starter culture contains a community of microbes made up of yeasts and bacteria, which ferment the carbohydrates in flour and produce the carbon dioxide gas that makes the bread dough rise before baking. The different acids and enzymes produced by the microbial culture affect the bread's flavor, texture and shelf life. However, for such a dependable staple, sourdough bread cultures and the mixture of microbes they contain have scarcely been characterized. Previous studies have looked at the composition of starter cultures from regions within Europe. But there has never been a comprehensive study of how the microbial diversity of sourdough starters varies across and between continents. To investigate this, Landis, Oliverio et al. used genetic sequencing to characterize the microbial communities of sourdough starters from the homes of 500 bread bakers in North America, Europe and Australasia. Bread makers often think their bread's unique qualities are due to the local environment of where the sourdough starter was made. However, Landis, Oliverio et al. found that geographical location did not correlate with the diversity of the starter cultures studied. The data revealed that a group of microbes called acetic acid bacteria, which had been overlooked in past research, were relatively common in starter cultures. Moreover, starters with a greater abundance of this group of bacteria produced bread with a strong vinegar aroma and caused dough to rise at a slower rate. This research demonstrates which species of bacteria and yeast are most commonly found in sourdough starters, and suggests geographical location has little influence on the microbial diversity of these cultures. Instead, the diversity of microbes likely depends more on how the starter culture was made and how it is maintained over time.

History and Domestication of Saccharomyces cerevisiae in Bread Baking.

The yeast Saccharomyces cerevisiae has been instrumental in the fermentation of foods and beverages for millennia. In addition to fermentations like wine, beer, cider, sake, and bread, S. cerevisiae has been isolated from environments ranging from soil and trees, to human clinical isolates. Each of these environments has unique selection pressures that S. cerevisiae must adapt to. Bread dough, for example, requires S. cerevisiae to efficiently utilize the complex sugar maltose; tolerate osmotic stress due to the semi-solid state of dough, high salt, and high sugar content of some doughs; withstand various processing conditions, including freezing and drying; and produce desirable aromas and flavors. In this review, we explore the history of bread that gave rise to modern commercial baking yeast, and the genetic and genomic changes that accompanied this. We illustrate the genetic and phenotypic variation that has been documented in baking strains and wild strains, and how this variation might be used for baking strain improvement. While we continue to improve our understanding of how baking strains have adapted to bread dough, we conclude by highlighting some of the remaining open questions in the field.

Influences of Ingredients and Bakers on the Bacteria and Fungi in Sourdough Starters and Bread.

Sourdough starters are naturally occurring microbial communities in which the environment, ingredients, and bakers are potential sources of microorganisms. The relative importance of these pools remains unknown. Here, bakers from two continents used a standardized recipe and ingredients to make starters that were then baked into breads. We characterized the fungi and bacteria associated with the starters, bakers' hands, and ingredients using 16S and internal transcribed spacer (ITS) rRNA gene amplicon sequencing and then measured dough acidity and bread flavor. Starter communities were much less uniform than expected, and this variation manifested in the flavor of the bread. Starter communities were most similar to those found in flour but shared some species with the bakers' skin. While humans likely contribute microorganisms to the starters, the reverse also appears to be true. This bidirectional exchange of microorganisms between starters and bakers highlights the importance of microbial diversity on bodies and in our environments as it relates to foods.IMPORTANCE Sourdough starters are complex communities of yeast and bacteria which confer characteristic flavor and texture to sourdough bread. The microbes present in starters can be sourced from ingredients or the baking environment and are typically consistent over time. Herein, we show that even when the recipe and ingredients for starter and bread are identical, different bakers around the globe produce highly diverse starters which then alter bread acidity and flavor. Much of the starter microbial community comes from bread flour, but the diversity is also associated with differences in the microbial community on the hands of bakers. These results indicate that bakers may be a source for yeast and bacteria in their breads and/or that bakers' jobs are reflected in their skin microbiome.

Azteca ants maintain unique microbiomes across functionally distinct nest chambers.

The microbiome of built structures has considerable influence over an inhabitant's well-being, yet the vast majority of research has focused on human-built structures. Ants are well-known architects, capable of constructing elaborate dwellings, the microbiome of which is underexplored. Here, we explore the bacterial and fungal microbiomes in functionally distinct chambers within and outside the nests of Azteca alfari ants in Cecropia peltata trees. We predicted that A. alfari colonies (1) maintain distinct microbiomes within their nests compared to the surrounding environment, (2) maintain distinct microbiomes among nest chambers used for different functions, and (3) limit both ant and plant pathogens inside their nests. In support of these predictions, we found that internal and external nest sampling locations had distinct microbial communities, and A. alfari maintained lower bacterial richness in their 'nurseries'. While putative animal pathogens were suppressed in chambers that ants actively inhabited, putative plant pathogens were not, which does not support our hypothesis that A. alfari defends its host trees against microbial antagonists. Our results show that ants influence microbial communities inside their nests similar to studies of human homes. Unlike humans, ants limit the bacteria in their nurseries and potentially prevent the build-up of insect-infecting pathogens. These results highlight the importance of documenting how indoor microbiomes differ among species, which might improve our understanding of how to promote indoor health in human dwellings.

Metagenomic analyses reveal previously unrecognized variation in the diets of sympatric Old World monkey species.

Insectivory, or the consumption of insects and other arthropods, is a significant yet cryptic component of omnivorous primate diets. Here, we used high-throughput DNA sequencing to identify arthropods from fecal DNA and assess variation in insectivory by closely-related sympatric primates. We identified arthropod prey taxa and tested the hypothesis that variation in insectivory facilitates niche differentiation and coexistence among closely-related species with high dietary overlap. We collected 233 fecal samples from redtail (Cercopithecus ascanius; n = 118) and blue monkeys (C. mitis; n = 115) and used a CO1 metabarcoding approach to identify arthropod DNA in each fecal sample. Arthropod DNA was detected in 99% of samples (N = 223 samples), and a total of 68 families (15 orders) were identified. Redtails consumed arthropods from 54 families, of which 12 (21.8%) were absent from blue monkey samples. Blue monkeys consumed arthropods from 56 families, of which 14 (24.6%) were absent from redtail samples. For both species, >97% of taxa present belonged to four orders (Araneae, Diptera, Hymenoptera, Lepidoptera). Redtail samples contained more Lepidoptera taxa (p<0.05), while blue monkey samples contained more Araneae (p<0.05). Blue monkeys consumed a greater diversity of arthropod taxa than redtail monkeys (p<0.05); however, the average number of arthropod families present per fecal sample was greater in the redtail monkey samples (p<0.05). These results indicate that while overlap exists in the arthropod portion of their diets, 20-25% of taxa consumed are unique to each group. Our findings suggest that variation in arthropod intake may help decrease dietary niche overlap and hence facilitate coexistence of closely-related primate species.

The ecology of insect-yeast relationships and its relevance to human industry.

Many species of yeast are integral to human society. They produce many of our foods, beverages and industrial chemicals, challenge us as pathogens, and provide models for the study of our own biology. However, few species are regularly studied and much of their ecology remains unclear, hindering the development of knowledge that is needed to improve the relationships between humans and yeasts. There is increasing evidence that insects are an essential component of ascomycetous yeast ecology. We propose a 'dispersal-encounter hypothesis' whereby yeasts are dispersed by insects between ephemeral, spatially disparate sugar resources, and insects, in turn, obtain the benefits of an honest signal from yeasts for the sugar resources. We review the relationship between yeasts and insects through three main examples: social wasps, social bees and beetles, with some additional examples from fruit flies. Ultimately, we suggest that over the next decades, consideration of these ecological and evolutionary relationships between insects and yeasts will allow prediction of where new yeast diversity is most likely to be discovered, particularly yeasts with traits of interest to human industry.

The emerging contribution of social wasps to grape rot disease ecology.

Grape sour (bunch) rot is a polymicrobial disease of vineyards that causes millions of dollars in lost revenue per year due to decreased quality of grapes and resultant wine. The disease is associated with damaged berries infected with a community of acetic acid bacteria, yeasts, and filamentous fungi that results in rotting berries with high amounts of undesirable volatile acidity. Many insect species cause the initial grape berry damage that can lead to this disease, but most studies have focused on the role of fruit flies in facilitating symptoms and vectoring the microorganisms of this disease complex. Like fruit flies, social wasps are abundant in vineyards where they feed on ripe berries and cause significant damage, while also dispersing yeasts involved in wine fermentation. Despite this, their possible role in disease facilitation and dispersal of grape rots has not been explored. We tested the hypothesis that the paper wasp Polistes dominulus could facilitate grape sour rot in the absence of other insect vectors. Using marker gene sequencing we characterized the bacterial and fungal community of wild-caught adults. We used a sterilized foraging arena to determine if these wasps transfer viable microorganisms when foraging. We then tested if wasps harboring their native microbial community, or those inoculated with sour rot, had an effect on grape sour rot incidence and severity using a laboratory foraging arena. We found that all wasps harbor some portion of the sour rot microbial community and that they have the ability to transfer viable microorganisms when foraging. Foraging by inoculated and uninoculated wasps led to an increase in berry rot disease symptom severity and incidence. Our results indicate that paper wasps can facilitate sour rot diseases in the absence of other vectors and that the mechanism of this facilitation may include both increasing host susceptibility and transmitting these microbial communities to the grapes. Social wasps are understudied but relevant players in the sour rot ecology of vineyards.

The diversity of arthropods in homes across the United States as determined by environmental DNA analyses.

We spend most of our lives inside homes, surrounded by arthropods that impact our property as pests and our health as disease vectors and producers of sensitizing allergens. Despite their relevance to human health and well-being, we know relatively little about the arthropods that exist in our homes and the factors structuring their diversity. As previous work has been limited in scale by the costs and time associated with collecting arthropods and the subsequent morphological identification, we used a DNA-based method for investigating the arthropod diversity in homes via high-throughput marker gene sequencing of home dust. Settled dust samples were collected by citizen scientists from both inside and outside more than 700 homes across the United States, yielding the first continental-scale estimates of arthropod diversity associated with our residences. We were able to document food webs and previously unknown geographic distributions of diverse arthropods - from allergen producers to invasive species and nuisance pests. Home characteristics, including the presence of basements, home occupants and surrounding land use, were more useful than climate parameters in predicting arthropod diversity in homes. These noninvasive, scalable tools and resultant findings not only provide the first continental-scale maps of household arthropod diversity, but our analyses also provide valuable baseline information on arthropod allergen exposures and the distributions of invasive pests inside homes.

Microbes Should Be Central to Ecological Education and Outreach.

Our planet is changing rapidly, and responding to the ensuing environmental challenges will require an informed citizenry that can understand the inherent complexity of ecological systems. However, microorganisms are usually neglected in the narratives that we use to understand nature. Here, we advocate for the inclusion of microbial ecology across education levels and delineate the often neglected benefits of incorporating microbes into ecology curricula. We provide examples across education levels, from secondary school (by considering one's self as a microbial ecosystem), to higher education (by incorporating our knowledge of the global ecological role and medical application of microbes), to the general public (by engagement through citizen-science projects). The greater inclusion of microbes in ecological education and outreach will not only help us appreciate the natural world we are part of, but will ultimately aid in building a citizenry better prepared to make informed decisions on health and environmental policies.

Actinomycetes with antimicrobial activity isolated from paper wasp (Hymenoptera: Vespidae: Polistinae) nests.

Actinomycetes-a group of antimicrobial producing bacteria-have been successfully cultured and characterized from the nest material of diverse arthropods. Some are symbionts that produce antimicrobial chemicals found to protect nest brood and resources from pathogenic microbes. Others have no known fitness relationship with their associated insects, but have been found to produce antimicrobials in vitro. Consequently, insect nest material is being investigated as a new source of novel antimicrobial producing actinomycetes, which could be harnessed for therapeutic potential. To extend studies of actinomycete-insect associations beyond soil-substrate dwelling insects and wood boring excavators, we conducted a preliminary assessment of the actinomycetes within the nests of the paper wasp, Polistes dominulus (Christ). We found that actinomycetes were readily cultured from nest material across multiple invasive P. dominulus populations-including members of the genera Streptomyces, Micromonospora, and Actinoplanes. Thirty of these isolates were assayed for antimicrobial activity against the challenge bacteria Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Serratia marcescens, and Bacillus subtilis. Sixty percent of isolates inhibited the growth of at least one challenge strain. This study provides the first assessment of bacteria associated with nests of P. dominulus, and the first record of antimicrobial producing actinomycetes isolated from social wasps. We provide a new system to explore nest associated actinomycetes from a ubiquitous and cosmopolitan group of insects.

Sex-related differences in alkaloid chemical defenses of the dendrobatid frog Oophaga pumilio from Cayo Nancy, Bocas del Toro, Panama.

Poison frogs contain an alkaloid-based chemical defense that is sequestered directly from a diet of alkaloid-containing arthropods. Geographic and temporal variation in alkaloid defense is common in poison frogs and is generally attributed to differences in the availability of alkaloid-containing arthropods. Variable chemical defense in poison frogs may have important consequences for predator-prey interactions, requiring a full understanding of the factors involved in explaining such variation. In the present study, we examine alkaloid variation in the dendrobatid poison frog Oophaga pumilio between males and females on Cayo Nancy (Isla Solarte), located in the Bocas del Toro archipelago of Panama. On average, females contained a significantly larger number and quantity of alkaloids when compared to males. Alkaloid composition varied significantly between males and females, illustrating that chemical defense in this population of O. pumilio is sex-dependent. The variation in alkaloids between sexes is attributed to differences in feeding and behavior between males and females. The majority of alkaloids present in the skin of O. pumilio appear to be of oribatid mite origin, supporting the importance of these dietary arthropods in the chemical defense of poison frogs.

Neocitreamicins I and II, novel antibiotics with activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci.

Two novel antibiotics, neocitreamicins I and II, were isolated from a fermentation broth of a Nocardia strain. This producing strain was obtained using an in situ diffusion chamber that facilitates the cultivation of soil microorganisms. The structures of neocitreamicins I and II were elucidated using UV, MS, and NMR data, and found to be related to the polycyclic xanthone antibiotics of the citreamicin class. The neocitreamicins showed in vitro activity against Gram-positive bacteria including strains of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis.