Integrative single-cell characterization of a frugivorous and an insectivorous bat kidney and pancreas.

Frugivory evolved multiple times in mammals, including bats. However, the cellular and molecular components driving it remain largely unknown. Here, we use integrative single-cell sequencing (scRNA-seq and scATAC-seq) on insectivorous (Eptesicus fuscus; big brown bat) and frugivorous (Artibeus jamaicensis; Jamaican fruit bat) bat kidneys and pancreases and identify key cell population, gene expression and regulatory differences associated with the Jamaican fruit bat that also relate to human disease, particularly diabetes. We find a decrease in loop of Henle and an increase in collecting duct cells, and differentially active genes and regulatory elements involved in fluid and electrolyte balance in the Jamaican fruit bat kidney. The Jamaican fruit bat pancreas shows an increase in endocrine and a decrease in exocrine cells, and differences in genes and regulatory elements involved in insulin regulation. We also find that these frugivorous bats share several molecular characteristics with human diabetes. Combined, our work provides insights from a frugivorous mammal that could be leveraged for therapeutic purposes.

The genome sequence of Molossusnigricans (Chiroptera, Molossidae; Miller, 1902).

We present a genome assembly from an individual male Molossus nigricans (Chordata; Mammalia; Chiroptera; Molossidae). The genome sequence is 2.41 gigabases in span. The majority of the assembly is scaffolded into 24 chromosomal pseudomolecules, with the X sex chromosome assembled.

Integrative single-cell characterization of frugivory adaptations in the bat kidney and pancreas.

Frugivory evolved multiple times in mammals, including bats. However, the cellular and molecular components driving it remain largely unknown. Here, we used integrative single-cell sequencing on insectivorous and frugivorous bat kidneys and pancreases and identified key cell population, gene expression and regulatory element differences associated with frugivorous adaptation that also relate to human disease, particularly diabetes. We found an increase in collecting duct cells and differentially active genes and regulatory elements involved in fluid and electrolyte balance in the frugivore kidney. In the frugivorous pancreas, we observed an increase in endocrine and a decrease in exocrine cells and differences in genes and regulatory elements involved in insulin regulation. Combined, our work provides novel insights into frugivorous adaptation that also could be leveraged for therapeutic purposes.

An Environmental DNA Primer for Microbial and Restoration Ecology.

Environmental DNA (eDNA) sequencing-DNA collected from the environment from living cells or shed DNA-was first developed for working with microbes and has greatly benefitted microbial ecologists for decades since. These tools have only become increasingly powerful with the advent of metabarcoding and metagenomics. Most new studies that examine diverse assemblages of bacteria, archaea, protists, fungi, and viruses lean heavily into eDNA using these newer technologies, as the necessary sequencing technology and bioinformatic tools have become increasingly affordable and user friendly. However, eDNA methods are rapidly evolving, and sometimes it can feel overwhelming to simply keep up with the basics. In this review, we provide a starting point for microbial ecologists who are new to DNA-based methods by detailing the eDNA methods that are most pertinent, including study design, sample collection and storage, selecting the right sequencing technology, lab protocols, equipment, and a few bioinformatic tools. Furthermore, we focus on how eDNA work can benefit restoration and what modifications are needed when working in this subfield.

Cascading effects of habitat loss on ectoparasite-associated bacterial microbiomes.

Suitable habitat fragment size, isolation, and distance from a source are important variables influencing community composition of plants and animals, but the role of these environmental factors in determining composition and variation of host-associated microbial communities is poorly known. In parasite-associated microbial communities, it is hypothesized that evolution and ecology of an arthropod parasite will influence its microbiome more than broader environmental factors, but this hypothesis has not been extensively tested. To examine the influence of the broader environment on the parasite microbiome, we applied high-throughput sequencing of the V4 region of 16S rRNA to characterize the microbiome of 222 obligate ectoparasitic bat flies (Streblidae and Nycteribiidae) collected from 155 bats (representing six species) from ten habitat fragments in the Atlantic Forest of Brazil. Parasite species identity is the strongest driver of microbiome composition. To a lesser extent, reduction in habitat fragment area, but not isolation, is associated with an increase in connectance and betweenness centrality of bacterial association networks driven by changes in the diversity of the parasite community. Controlling for the parasite community, bacterial network topology covaries with habitat patch area and exhibits parasite-species specific responses to environmental change. Taken together, habitat loss may have cascading consequences for communities of interacting macro- and microorgansims.

You are more than what you eat: potentially adaptive enrichment of microbiome functions across bat dietary niches.

BACKGROUND: Animals evolved in a microbial world, and their gut microbial symbionts have played a role in their ecological diversification. While many recent studies report patterns of phylosymbiosis between hosts and their gut bacteria, fewer studies examine the potentially adaptive functional contributions of these microbes to the dietary habits of their hosts. In this study, we examined predicted metabolic pathways in the gut bacteria of more than 500 individual bats belonging to 60 species and compare the enrichment of these functions across hosts with distinct dietary ecologies. RESULTS: We found that predicted microbiome functions were differentially enriched across hosts with different diets. Using a machine-learning approach, we also found that inferred microbiome functions could be used to predict specialized host diets with reasonable accuracy. We detected a relationship between both host phylogeny and diet with respect to microbiome functional repertoires. Because many predicted functions could potentially fill nutritional gaps for bats with specialized diets, we considered pathways discriminating dietary niches as traits of the host and fit them to comparative phylogenetic models of evolution. Our results suggest that some, but not all, predicted microbiome functions may evolve toward adaptive optima and thus be visible to the forces of natural selection operating on hosts over evolutionary time. CONCLUSIONS: Our results suggest that bats with specialized diets may partially rely on their gut microbes to fulfill or augment critical nutritional pathways, including essential amino acid synthesis, fatty acid biosynthesis, and the generation of cofactors and vitamins essential for proper nutrition. Our work adds to a growing body of literature suggesting that animal microbiomes are structured by a combination of ecological and evolutionary processes and sets the stage for future metagenomic and metabolic characterization of the bat microbiome to explore links between bacterial metabolism and host nutrition.

Differential effects of elevated nest temperature and parasitism on the gut microbiota of wild avian hosts.

BACKGROUND: Changes in wild animal gut microbiotas may influence host health and fitness. While many studies have shown correlations between gut microbiota structure and external factors, few studies demonstrate causal links between environmental variables and microbiota shifts. Here, we use a fully factorial experiment to test the effects of elevated ambient temperature and natural nest parasitism by nest flies (Protocalliphora sialia) on the gut microbiotas of two species of wild birds, the eastern bluebird (Sialia sialis) and the tree swallow (Tachycineta bicolor). RESULTS: We find that bacterial communities from the nestlings of each host species show idiosyncratic responses to both heat and parasitism, with gut microbiotas of eastern bluebirds more disrupted by heat and parasitism than those of tree swallows. Thus, we find that eastern bluebirds are unable to maintain stable associations with their gut bacteria in the face of both elevated temperature and parasitism. In contrast, tree swallow gut microbiotas are not significantly impacted by either heat or nest parasitism. CONCLUSIONS: Our results suggest that excess heat (e.g., as a result of climate change) may destabilize natural host-parasite-microbiota systems, with the potential to affect host fitness and survival in the Anthropocene.

Molecular diet analysis of neotropical bats based on fecal DNA metabarcoding.

Bat communities in the Neotropics are some of the most speciose assemblages of mammals on Earth, with regions supporting more than 100 sympatric species with diverse feeding ecologies. Because bats are small, nocturnal, and volant, it is difficult to directly observe their feeding habits, which has resulted in their classification into broadly defined dietary guilds (e.g., insectivores, carnivores, and frugivores). Apart from these broad guilds, we lack detailed dietary information for many species and therefore have only a limited understanding of interaction networks linking bats and their diet items. In this study, we used DNA metabarcoding of plants, arthropods, and vertebrates to investigate the diets of 25 bat species from the tropical dry forests of Lamanai, Belize. Our results report some of the first detection of diet items for the focal bat taxa, adding rich and novel natural history information to the field of bat ecology. This study represents a comprehensive first effort to apply DNA metabarcoding to bat diets at Lamanai and provides a useful methodological framework for future studies testing hypotheses about coexistence and niche differentiation in the context of modern high-throughput molecular data.

16S rRNA Amplicon Sequencing of Urban Prokaryotic Communities in the South Bronx River Estuary.

Biodiversity monitoring is an essential component of restoration efforts. We sequenced 16S rRNA gene amplicons from sediments and waters of Hunts Point Riverside Park and Soundview Park, located in a historically degraded but recovering urban estuary in New York. In total, 16,165 unique amplicon sequence variants were recovered, and Proteobacteria was the dominant phylum.

Habitat fragmentation is associated with dietary shifts and microbiota variability in common vampire bats.

Host ecological factors and external environmental factors are known to influence the structure of gut microbial communities, but few studies have examined the impacts of environmental changes on microbiotas in free-ranging animals. Rapid land-use change has the potential to shift gut microbial communities in wildlife through exposure to novel bacteria and/or by changing the availability or quality of local food resources. The consequences of such changes to host health and fitness remain unknown and may have important implications for pathogen spillover between humans and wildlife. To better understand the consequences of land-use change on wildlife microbiotas, we analyzed long-term dietary trends, gut microbiota composition, and innate immune function in common vampire bats (Desmodus rotundus) in two nearby sites in Belize that vary in landscape structure. We found that vampire bats living in a small forest fragment had more homogenous diets indicative of feeding on livestock and shifts in microbiota heterogeneity, but not overall composition, compared to those living in an intact forest reserve. We also found that irrespective of sampling site, vampire bats which consumed relatively more livestock showed shifts in some core bacteria compared with vampire bats which consumed relatively less livestock. The relative abundance of some core microbiota members was associated with innate immune function, suggesting that future research should consider the role of the host microbiota in immune defense and its relationship to zoonotic infection dynamics. We suggest that subsequent homogenization of diet and habitat loss through livestock rearing in the Neotropics may lead to disruption to the microbiota that could have downstream impacts on host immunity and cross-species pathogen transmission.

Bats Are an Untapped System for Understanding Microbiome Evolution in Mammals.

Mammals evolved in a microbial world, and consequently, microbial symbionts have played a role in their evolution. An exciting new subdiscipline of metagenomics considers the ways in which microbes, particularly those found in the gut, have facilitated the ecological and phylogenetic radiation of mammals. However, the vast majority of such studies focus on domestic animals, laboratory models, or charismatic megafauna (e.g., pandas and chimpanzees). The result is a plethora of studies covering few taxa across the mammal tree of life, leaving broad patterns of microbiome function and evolution unclear. Wildlife microbiome research urgently needs a model system in which to test hypotheses about metagenomic involvement in host ecology and evolution. We propose that bats (Order: Chiroptera) represent a model system ideal for comparative microbiome research, affording opportunities to examine host phylogeny, diet, and other natural history characteristics in relation to the evolution of the gut microbiome.

The Antifungal Properties of Epidermal Fatty Acid Esters: Insights from White-Nose Syndrome (WNS) in Bats.

Numerous free fatty acids (FFAs) are known to have potent antifungal effects. The mammalian epidermis contains both FFAs and multiple classes of fatty acid esters, including 1-monoacylglycerols and wax esters. We thus hypothesized that wax esters and 1-monoacylglycerols composed of antifungal fatty acids would also have antifungal properties. We tested this hypothesis by examining the effects of 1-monoacylglycerols, 1,3-diacylglycerols, and wax esters on the growth of Pseudogymnoascus destructans (Pd), the fungus that causes White-nose Syndrome (WNS) in North American bats by invading their epidermis. Laboratory experiments with Pd cultures demonstrated that: (a) three 1-monoacylglycerols (1-monopalmitolein, 1-monoolein, and 1-monolinolein), as well as, (b) two wax esters, behenyl oleate and behenyl palmitoleate, profoundly inhibit Pd growth. The normal growth cycle of Pd was interrupted by addition of two cholesterol esters to the media as well. A bat species resistant to cutaneous Pd infections has these 1-monoacylglycerols in the epidermis, and another Pd resistant bat species has these wax esters in the sebum, thus cutaneous lipid composition is one factor which enables some bats to avoid WNS. Our experiments also revealed that the fatty acid esters which inhibit Pd growth are not hydrolyzed by the lipases secreted by this fungus, whereas the esters that do not inhibit Pd growth are hydrolyzed.

Comparing Microbiome Sampling Methods in a Wild Mammal: Fecal and Intestinal Samples Record Different Signals of Host Ecology, Evolution.

The gut microbiome is a community of host-associated symbiotic microbes that fulfills multiple key roles in host metabolism, immune function, and tissue development. Given the ability of the microbiome to impact host fitness, there is increasing interest in studying the microbiome of wild animals to better understand these communities in the context of host ecology and evolution. Human microbiome research protocols are well established, but wildlife microbiome research is still a developing field. Currently, there is no standardized set of best practices guiding the collection of microbiome samples from wildlife. Gut microflora are typically sampled either by fecal collection, rectal swabbing, or by destructively sampling the intestinal contents of the host animal. Studies rarely include more than one sampling technique and no comparison of these methods currently exists for a wild mammal. Although some studies have hypothesized that the fecal microbiome is a nested subset of the intestinal microbiome, this hypothesis has not been formally tested. To address these issues, we examined guano (feces) and distal intestinal mucosa from 19 species of free-ranging bats from Lamanai, Belize, using 16S rRNA amplicon sequencing to compare microbial communities across sample types. We found that the diversity and composition of intestine and guano samples differed substantially. In addition, we conclude that signatures of host evolution are retained by studying gut microbiomes based on mucosal tissue samples, but not fecal samples. Conversely, fecal samples retained more signal of host diet than intestinal samples. These results suggest that fecal and intestinal sampling methods are not interchangeable, and that these two microbiotas record different information about the host from which they are isolated.

The effects of epidermal fatty acid profiles, 1-oleoglycerol, and triacylglycerols on the susceptibility of hibernating bats to Pseudogymnoascus destructans.

White Nose Syndrome (WNS) greatly increases the over-winter mortality of little brown (Myotis lucifugus), Indiana (M. sodalis), northern (M. septentrionalis), and tricolored (Perimyotis subflavus) bats, and is caused by cutaneous infections with Pseudogymnoascus destructans (Pd). Big brown bats (Eptesicus fuscus) are highly resistant to Pd infections. Seven different fatty acids (myristic, pentadecanoic, palmitic, palmitoleic, oleic, and, linoleic acids) occur in the wing epidermis of both M. lucifugus and E. fuscus, 4 of which (myristic, palmitoleic, oleic, and, linoleic acids) inhibit Pd growth. The amounts of myristic and linoleic acids in the epidermis of M. lucifugus decrease during hibernation, thus we predicted that the epidermal fatty acid profile of M. lucifugus during hibernation has a reduced ability to inhibit Pd growth. Laboratory Pd growth experiments were conducted to test this hypothesis. The results demonstrated that the fatty acid profile of M. lucifugus wing epidermis during hibernation has a reduced ability to inhibit the growth of Pd. Additional Pd growth experiments revealed that: a) triacylglycerols composed of known anti-Pd fatty acids do not significantly affect growth, b) pentadecanoic acid inhibits Pd growth, and c) 1-oleoglycerol, which is found in the wing epidermis of E. fuscus, also inhibits the growth of this fungus. Analyses of white adipose from M. lucifugus also revealed the selective retention of oleic and linoleic acids in this tissue during hibernation.

The Effects of Cutaneous Fatty Acids on the Growth of Pseudogymnoascus destructans, the Etiological Agent of White-Nose Syndrome (WNS).

White Nose Syndrome (WNS) greatly increases the over-winter mortality of little brown (Myotis lucifugus), Indiana (Myotis sodalis), northern (Myotis septentrionalis), and tricolored (Perimyotis subflavus) bats. It is caused by a cutaneous infection with the fungus Pseudogymnoascus destructans (Pd). Big brown bats (Eptesicus fuscus) are much more resistant to cutaneous infection with Pd, however. We thus conducted analyses of wing epidermis from hibernating E. fuscus and M. lucifugus to determine their fatty acid compositions, and laboratory Pd culture experiments at 4.0-13.4°C to determine the effects of these fatty acids on Pd growth. Our analyses revealed that the epidermis of both bat species contain the same 7 fatty acid types (14:0, 15:0, 16:0. 16:1, 18:0, 18:1, & 18:2), but the epidermis of M. lucifugus contains: a) more stearic (18:0) acid, b) less palmitoleic (16:1) acid, c) less myristic (14:0) acid, and, d) less oleic (18:1) acid than that of E. fuscus. The growth of Pd was inhibited by: a) myristic and stearic acids at 10.5-13.4°C, but not at 4.0-5.0°C, b) oleic acid at 5.0-10.6°C, c) palmitoleic acid, and, d) linoleic (18:2) acid at 5.0-10.6°C. One set of factors that enables E. fuscus to better resist cutaneous P. destructans infections (and thus WNS) therefore appears to be the relatively higher myristic, palmitoleic, and oleic acid contents of the epidermis.