Wastewater treatment works change the intestinal microbiomes of insectivorous bats

Viromes of arthropod parasites and their hosts: The case of bats and bat ectoparasites

Blood feeding ectoparasites of bats have been found to contain insect-specific and vertebrate-infecting viruses of agricultural and medical importance. While it is plausible that some of these are of bat origin, those would be sourced either from the bat exterior or their blood meal. Bats, in addition to their regular diets, consume numerous ectoparasites during grooming. All microbes on and in the ectoparasites would then be introduced into the bat gut upon ingestion of the ectoparasites. To investigate the potential impact of bat ectoparasite viromes on the gut viral microbiome of bats, we compared virus sequences from bats and their blood feeding ectoparasites collected from Yunnan Province, China. Although all the co-occurring viruses were bacteriophages, we observed that bats contained a larger set of viruses than their ectoparasites, and that the set of predicted viruses present in the bats were more diverse than those present in bat ectoparasites. Our analysis suggests that despite a heavy influx of ectoparasites into the digestive tract of bats through consumption, there are only few co-occurring/shared viruses between bats and their ectoparasites, and that these ectoparasites may not be a major driver of bat virome diversity. Our findings provide necessary preliminary data for the evaluation of bat ectoparasites as a potential source of bat infecting viruses.

Shift in diet composition of a riparian predator along a stream pollution gradient

Terrestrial insectivores in riparian areas, such as spiders, can depend on emergent aquatic insects as high-quality prey. However, chemical pollution entering streams from agricultural and urban sources can alter the dynamics and composition of aquatic insect emergence, which may also affect the riparian food web. Few studies have examined the effects of stressor-induced alterations in aquatic insect emergence on spiders, especially in terms of chemical pollution and diet composition. We used DNA metabarcoding of gut content to describe the diet of Tetragnatha montana spiders collected from 10 forested streams with differing levels of pesticide and wastewater pollution. We found that spiders consumed more Chironomidae and fewer other aquatic Diptera, including Tipulidae, Ptychopteridae and Culicidae, at more polluted streams. Pollution-related effects were mainly observed in the spider diet, and were not significant for the number nor composition of flying insects trapped at each site. Our results indicate that the composition of riparian spider diets is sensitive to stream pollution, even in the absence of a change in the overall proportion of aquatic prey consumed. A high reliance on aquatic prey at polluted streams may give spiders an increased risk of dietary exposure to chemical pollutants retained by emergent insects.

Increased bat hunting at polluted streams suggests chemical exposure rather than prey shortage

Streams and their riparian areas are important habitats and foraging sites for bats feeding on emergent aquatic insects. Chemical pollutants entering freshwater streams from agricultural and wastewater sources have been shown to alter aquatic insect emergence, yet little is known about how this impacts insectivorous bats in riparian areas. In this study, we investigate the relationships between the presence of wastewater effluent, in-stream pesticide toxicity, the number of emergent and flying aquatic insects, and the activity and hunting behaviour of bats at 14 streams in southwestern Germany. Stream sites were located in riparian forests, sheltered from direct exposure to pollutants from agricultural and urban areas. We focused on three bat species associated with riparian areas: Myotis daubentonii, M. cf. brandtii, and Pipistrellus pipistrellus. We found that streams with higher pesticide toxicity and more frequent detection of wastewater also tended to be warmer and have higher nutrient and lower oxygen concentrations. We did not observe a reduction of insect emergence, bat activity or hunting rates in association with pesticide toxicity and wastewater detections. Instead, the activity and hunting rates of Myotis spp. were higher at more polluted sites. The observed increase in bat hunting at more polluted streams suggests that instead of reduced prey availability, chemical pollution at the levels measured in the present study could expose bats to pollutants transported from the stream by emergent aquatic insects.

Characterization of the bacterial microbiome of non-hematophagous bats and associated ectoparasites from Brazil

Introduction

Bats, along with their ectoparasites, harbor a wide diversity of symbiotic and potential pathogenic bacteria. Despite the enormous diversity of bats (181 species), few studies aimed to investigate the bacterial microbiome of Brazilian chiropterans and associated ectoparasites. This study aimed to characterize the bacterial microbiome of non-hematophagous bats and associated Streblidae flies and Macronyssidae and Spinturnicidae mites in the state of Mato Grosso do Sul, midwestern Brazil.

Methods

Oral and rectal swabs were collected from 30 bats (Artibeus lituratus [n = 13], Artibeus planirostris [n  =  9], Eptesicus furinalis [n = 5], Carollia perspicillata [n = 2], and Platyrrhinus lineatus [n = 1]). In addition, a total of 58 mites (15 Macronyssidae and 43 Spinturnicidae) and 48 Streblidae bat flies were collected from the captured bats. After DNA extraction and purification, each sample's bacterial composition was analyzed with metagenomic sequencing.

Results

The microbiome composition of both oral and rectal bat swab samples showed that Gammaproteobacteria was the most abundant bacterial class. Spiroplasma, Wolbachia and Bartonella represented the most abundant genera in Streblidae flies. While Wolbachia (Alphaproteobacteria) was the most abundant genus found in Spinturnicidae, Arsenophonus (Gammaproteobacteria) was found in high abundance in Macronyssidae mites. In addition to characterizing the microbiome of each sample at the class and genus taxonomic levels, we identified medically significant bacteria able to infect both animals and humans in oral (Streptococcus and Anaplasma) and rectal swabs (Enterobacter, Klebsiella, Escherichia, Enterococcus, Streptococcus), Macronyssidae (Anaplasma, Bartonella, Ehrlichia) and Spinturnicidae (Anaplasma, Bartonella) mites as well as Streblidae flies (Spiroplasma, Bartonella).

Discussion and conclusion

Besides expanding the knowledge on the bacterial microbiome of non-hematophagous bats and Streblidae flies from Brazil, the present work showed, for the first time, the bacterial community of bat-associated Macronyssidae and Spinturnicidae mites.

Effects of anthropogenic stress on hosts and their microbiomes: Treated wastewater alters performance and gut microbiome of a key detritivore (Asellus aquaticus)

Human activity is a major driver of ecological and evolutionary change in wild populations and can have diverse effects on eukaryotic organisms as well as on environmental and host-associated microbial communities. Although host-microbiome interactions can be a major determinant of host fitness, few studies consider the joint responses of hosts and their microbiomes to anthropogenic changes. In freshwater ecosystems, wastewater is a widespread anthropogenic stressor that represents a multifarious environmental perturbation. Here, we experimentally tested the impact of treated wastewater on a keystone host (the freshwater isopod Asellus aquaticus) and its gut microbiome. We used a semi-natural flume experiment, in combination with 16S rRNA amplicon sequencing, to assess how different concentrations (0%, 30%, and 80%) of nonfiltered wastewater (i.e. with chemical toxicants, nutrients, organic particles, and microbes) versus ultrafiltered wastewater (i.e. only dissolved pollutants and nutrients) affected host survival, growth, and food consumption as well as mid- and hindgut bacterial community composition and diversity. Our results show that while host survival was not affected by the treatments, host growth increased and host feeding rate decreased with nonfiltered wastewater - potentially indicating that A. aquaticus fed on organic matter and microbes available in nonfiltered wastewater. Furthermore, even though the midgut microbiome (diversity and composition) was not affected by any of our treatments, nonfiltered wastewater influenced bacterial composition (but not diversity) in the hindgut. Ultrafiltered wastewater, on the other hand, affected both community composition and bacterial diversity in the hindgut, an effect that in our system differed between sexes. While the functional consequences of microbiome changes and their sex specificity are yet to be tested, our results indicate that different components of multifactorial stressors (i.e. different constituents of wastewater) can affect hosts and their microbiome in distinct (even opposing) manners and have a substantial impact on eco-evolutionary responses to anthropogenic stressors.

Bats and pollution: Genetic approaches in ecotoxicology

Environmental pollution drives the decline of species and, as flying mammals, bats can be considered to be excellent indicators of environmental quality, and the analysis of genetic biomarkers in these animals can provide important parameters for the assessment of environmental health. This review verifies the trends in pollution research, in particular, the use of genetic markers in the study of bats, based on a literature search of the Web of Science and Scopus platforms. Sixteen publications were identified during the search, which focused on the timeframe between 1996 and March 2022, including investigations of the effects of heavy metals, agricultural pesticides, and radiation. The studies were based primarily on the application of biomarkers for genotoxic analysis, including the comet assay, micronucleus test, and the Polymerase Chain Reaction (PCR). Only 55 bat species have been investigated up to now, that is, 4% of the 1447 currently recognized. In general, bats exposed to polluted environments presented a higher frequency of genotoxic and mutagenic damage than those sampled in clean environments. Given the importance of the diverse ecological functions provided by bats, including pest control, pollination, and seed dispersal, it is increasingly necessary to investigate the damage caused to the health of these animals exposed to areas with high concentrations of contaminants. Although genetic biomarkers have been used to investigate physiological parameters in bats for more than two decades, then, many knowledge gaps remain, worldwide, in terms of the number of species and localities investigated.

Altered microbiomes of aquatic macroinvertebrates and riparian spiders downstream of municipal wastewater effluents

Municipal wastewater treatment plants (WWTPs) contain numerous contaminants, including antimicrobials, that could affect the composition of the beneficial bacterial communities associated with host aquatic organisms. There is also potential for these effects to transfer to terrestrial predators. Riparian spiders and five families of aquatic macroinvertebrates were collected from sites upstream and downstream of two WWTPs, Waterloo and Kitchener, discharging to the Grand River, Ontario, Canada. Whole-body microbiota were analyzed following the extraction, PCR amplification, and sequencing of bacterial DNA using the V3-V4 hypervariable regions of the 16S rRNA genetic barcode. Changes in the relative abundance of major microbiome phyla were observed in all downstream aquatic insects except Hydropsychidae caddisflies, which exhibited little site variation. Shannon alpha diversity differed among sites for Tetragnathidae spiders, Perlidae, Hydropsychidae, and Heptageniidae. Downstream of the Waterloo WWTP alpha diversity decreased in spiders, while downstream of the Kitchener WWTP this measure decreased in Perlidae and increased in spiders. Bray-Curtis beta diversity was dissimilar among sites in all invertebrate taxa; upstream sites differed from those downstream of Waterloo in spiders, Perlidae, and Hydropsychidae, and from those downstream of Kitchener in spiders, Perlidae, and Hydropsychidae. Finally, effluent-derived bacteria were found in the microbiomes of downstream spiders and aquatic insects and not upstream. Overall, results indicated that the microbiomes of invertebrates collected downstream differed from those collected upstream of WWTPs, which has implications for altered host health and transport of WWTP-derived bacteria through aquatic ecosystems.