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The fungus gardening-ant system is considered a complex, multi-tiered symbiosis, as it is composed of ants, their fungus, and microorganisms associated with either ants or fungus. We examine the bacterial microbiome of Trachymyrmex septentrionalis and Mycetomoellerius turrifex ants and their symbiotic fungus gardens, using 16S rRNA Illumina sequencing, over a region spanning approximately 350 km (east and central Texas). Typically, microorganisms can be acquired from a parent colony (vertical transmission) or from the environment (horizontal transmission). Because the symbiosis is characterized by co-dispersal of the ants and fungus, elements of both ant and fungus garden microbiome could be characterized by vertical transmission. The goals of this study were to explore how both the ant and fungus garden bacterial microbiome are acquired. The main findings were that different mechanisms appear to explain the structure the microbiomes of ants and their symbiotic fungus gardens. Ant associated microbiomes had a strong host ant signature, which could be indicative of vertical inheritance of the ant associated bacterial microbiome or an unknown mechanism of active uptake or screening. On the other hand, the bacterial microbiome of the fungus garden was more complex in that some bacterial taxa appear to be structured by the ant host species, whereas others by fungal lineage or the environment (geographic region). Thus bacteria in fungus gardens appear to be acquired both horizontally and vertically., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Feathers are the habitat of a myriad of organisms, from fungi and bacteria to lice and mites. Although most studies focus on specific taxa and their interaction with the bird host, anecdotal data glimpse feathers as holders of a system with its own ecology, what we call here the stylosphere. A major gap in our knowledge of the stylosphere is the ecology of the total abundance of microorganisms, being also rare to find studies that analyze abundance of more than one group of microorganisms at the bird interspecific level. Here, we quantified bacterial and fungi abundances through qPCR on the wing feathers of 144 birds from 24 passerine and one non-passerine bird species from three localities in Southern Spain. Bacteria and fungi abundances spanned three orders of magnitude among individual birds, but were consistent when comparing the right and the left wing feathers of individuals. Sampling locality explained ca. 14% of the variation in both bacteria and fungi abundances. Even when statistically controlling for sampling locality, microbial abundances consistently differed between birds from different species, but these differences were not explained by bird phylogeny. Finally, bird individuals and species having more bacteria also tended to held larger abundances of fungi. Our results suggest a quite complex explanation for stylosphere microorganisms' abundance, being shaped by bird individual and species traits, as well as environmental factors, and likely bacteria–fungi interactions. [ABSTRACT FROM AUTHOR]

Hibernation represents a state of fasting because hibernators cease eating in the torpid periods. Therefore, food deprivation during hibernation is expected to modify the gut microbiota of host. However, there are few reports of gut microbiota in food-storing hibernators that feed during the interbout arousals. Here we collected fecal samples of Siberian chipmunk T. sibiricus to character and examine changes in the gut microbiota at various stages relative to hibernation: pre-hibernation, early-hibernation, mid-hibernation, late-hibernation, and post-hibernation. Compared to the pre-hibernation state, alpha-diversity of gut microbiota was significantly increased during the interbout arousal periods. In addition, beta-diversity of the fecal communities from pre-hibernation and interbout arousal periods grouped together, and post-hibernation gut microbiota resembled the counterpart at late-hibernation. Hibernation significantly decreased the relative abundance of Firmicutes but increased Bacteroidetes, reflecting a shift of microbiota toward taxa in favor of host-derived substrates. The increased abundance of Ruminococcaceae_UCG-014, Lactobacillus, and Christensenellaceae_R-7_group in gut microbiota may help the chipmunks reduce intestinal inflammation and then maintain healthy bowel during hibernation. KEGG pathway indicated that hibernation altered the metabolic function of gut microflora of T. sibiricus. Our study provides evidence that the gut microbiota of food-storing hibernators, despite feeding during the interbout arousals, shows similar response to hibernation that has well documented in fat-storing counterparts, suggesting the potential for a core gut microbiota during hibernation of mammals. Importantly, these results will broaden our understanding of the effects of hibernation on gut microbiota of mammal hibernators., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Bacterial members of the coral holobiont play an important role in determining coral fitness. However, most knowledge of the coral microbiome has come from reef-building scleractinian corals, with far less known about the nature and importance of the microbiome of octocorals (subclass Octocorallia), which contribute significantly to reef biodiversity and functional complexity. We examined the diversity and structure of the bacterial component of octocoral microbiomes over summer and winter, with a focus on two temperate (Erythropodium hicksoni, Capnella gaboensis; Sydney Harbour) and two tropical (Sinularia sp., Sarcophyton sp.; Heron Island) species common to reefs in eastern Australia. Bacterial communities associated with these octocorals were also compared to common temperate (Plesiastrea versipora) and tropical (Acropora aspera) hard corals from the same reefs. Using 16S rRNA amplicon sequencing, bacterial diversity was found to be heterogeneous among octocorals, but we observed changes in composition between summer and winter for some species (C. gaboensis and Sinularia sp.), but not for others (E. hicksoni and Sarcophyton sp.). Bacterial community structure differed significantly between all octocoral species within both the temperate and tropical environments. However, on a seasonal basis, those differences were less pronounced. The microbiomes of C. gaboensis and Sinularia sp. were dominated by bacteria belonging to the genus Endozoicomonas, which were a key conserved feature of their core microbiomes. In contrast to previous studies, our analysis revealed that Endozoicomonas phylotypes are shared across different octocoral species, inhabiting different environments. Together, our data demonstrates that octocorals harbour a broad diversity of bacterial partners, some of which comprise 'core microbiomes' that potentially impart important functional roles to their hosts., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The relationships between symbionts and insects are complex, and symbionts usually have diverse ecological and evolutionary effects on their hosts. The phloem sap-sucking aphids are good models to study the interactions between insects and symbiotic microorganisms. Although aphids usually exhibit remarkable life cycle complexity, most previous studies on symbiotic diversity sampled only apterous viviparous adult females or very few morphs. In this study, high-throughput 16S rDNA amplicon sequencing was used to assess the symbiotic bacterial communities of eleven morphs or developmental stages of the social aphid Pseudoregma bambucicola. We found there were significant differences in bacterial composition in response to different morphs and developmental stages, and for the first time, we revealed male aphids hosted very different symbiotic composition featured with low abundance of dominant symbionts but high diversity of total symbionts. The relative abundance of Pectobacterium showed relatively stable across different types of samples, while that of Wolbachia fluctuated greatly, indicating the former may have a consistent function in this species and the latter may provide specific function for certain morphs or developmental stages. Our study presents new evidence of complexity of symbiotic associations and indicates strong linkage between symbiotic bacterial community and host age and morph. [ABSTRACT FROM AUTHOR]

Although tunas represent a significant part of the global fish economy and a major nutritional resource worldwide, their microbiome still remains poorly documented. Here, we conducted an analysis of the taxonomic composition of the bacterial communities inhabiting the gut, skin, and liver of two most consumed tropical tuna species (skipjack and yellowfin), from individuals caught in the Atlantic and Indian oceans. We hypothesized that each organ harbors a specific microbial assemblage whose composition might vary according to different biotic (sex, species) and/or abiotic (environmental) factors. Our results revealed that the composition of the tuna microbiome was totally independent of fish sex, regardless of the species and ocean considered. Instead, the main determinants of observed diversity were (i) tuna species for the gut and (ii) sampling site for the skin mucus layer and (iii) a combination of both parameters for the liver. Interestingly, 4.5% of all amplicon sequence variants (ASV) were shared by the three organs, highlighting the presence of a core-microbiota whose most abundant representatives belonged to the genera Mycoplasma, Cutibacterium, and Photobacterium. Our study also revealed the presence of a unique and diversified bacterial assemblage within the tuna liver, comprising a substantial proportion of potential histamine-producing bacteria, well known for their pathogenicity and their contribution to fish poisoning cases. These results indicate that this organ is an unexplored microbial niche whose role in the health of both the host and consumers remains to be elucidated. [ABSTRACT FROM AUTHOR]

The coral holobiont is comprised of a highly diverse microbial community that provides key services to corals such as protection against pathogens and nutrient cycling. The coral surface mucus layer (SML) microbiome is very sensitive to external changes, as it constitutes the direct interface between the coral host and the environment. Here, we investigate whether the bacterial taxonomic and functional profiles in the coral SML are shaped by the local reef zone and explore their role in coral health and ecosystem functioning. The analysis was conducted using metagenomes and metagenome-assembled genomes (MAGs) associated with the coral Pseudodiploria strigosa and the water column from two naturally distinct reef environments in Bermuda: inner patch reefs exposed to a fluctuating thermal regime and the more stable outer reefs. The microbial community structure in the coral SML varied according to the local environment, both at taxonomic and functional levels. The coral SML microbiome from inner reefs provides more gene functions that are involved in nutrient cycling (e.g., photosynthesis, phosphorus metabolism, sulfur assimilation) and those that are related to higher levels of microbial activity, competition, and stress response. In contrast, the coral SML microbiome from outer reefs contained genes indicative of a carbohydrate-rich mucus composition found in corals exposed to less stressful temperatures and showed high proportions of microbial gene functions that play a potential role in coral disease, such as degradation of lignin-derived compounds and sulfur oxidation. The fluctuating environment in the inner patch reefs of Bermuda could be driving a more beneficial coral SML microbiome, potentially increasing holobiont resilience to environmental changes and disease. [ABSTRACT FROM AUTHOR]

Ants have long been known for their associations with other taxa, including macroscopic fungi and symbiotic bacteria. Recently, many ant species have had the composition and function of their bacterial communities investigated. Due to its behavioral and ecological diversity, the subfamily Ponerinae deserves more attention regarding its associated microbiota. Here, we used the V4 region of the 16S rRNA gene to characterize the bacterial communities of Odontomachus chelifer (ground-nesting) and Odontomachus hastatus (arboreal), two ponerine trap-jaw species commonly found in the Brazilian savanna ("Cerrado") and Atlantic rainforest. We investigated habitat effects (O. chelifer in the Cerrado and the Atlantic rainforest) and species-specific effects (both species in the Atlantic rainforest) on the bacterial communities' structure (composition and abundance) in two different body parts: cuticle and gaster. Bacterial communities differed in all populations studied. Cuticular communities were more diverse, while gaster communities presented variants common to other ants, including Wolbachia and Candidatus Tokpelaia hoelldoblerii. Odontomachus chelifer populations presented different communities in both body parts, highlighting the influence of habitat type. In the Atlantic rainforest, the outcome depended on the body part targeted. Cuticular communities were similar between species, reinforcing the habitat effect on bacterial communities, which are mainly composed of environmentally acquired taxa. Gaster communities, however, differed between the two Odontomachus species, suggesting species-specific effects and selective filters. Unclassified Firmicutes and uncultured Rhizobiales variants are the main components accounting for the observed differences. Our study indicates that both host species and habitat act synergistically, but to different degrees, to shape the bacterial communities in these Odontomachus species. [ABSTRACT FROM AUTHOR]

Host microbial communities are increasingly seen as an important component of host health. In amphibians, the first land vertebrates that are threatened by a fungal skin disease globally, our understanding of the factors influencing the microbiome of amphibian skin remains incomplete because recent studies have focused almost exclusively on bacteria, and little information exists on fungal communities associated with wild amphibian species. In this study, we describe the effects of host phylogeny, climate, geographic distance, and infection with a fungal pathogen on the composition and structure of bacterial and fungal communities in seven tropical salamander species that occur in the Trans-Mexican Volcanic Belt of Central Mexico. We find that host phylogenetic relatedness is correlated with bacterial community composition while a composite climatic variable of temperature seasonality and precipitation is significantly associated with fungal community composition. We also estimated co-occurrence networks for bacterial and fungal taxa and found differences in the degree of connectivity and the distribution of negative associations between the two networks. Our results suggest that different factors may be responsible for structuring the bacterial and fungal communities of amphibian skin and that the inclusion of fungi in future studies could shed light on important functional interactions within the microbiome. [ABSTRACT FROM AUTHOR]

Host genotype may shape host-associated bacterial communities (commonly referred to as microbiomes). We sought to determine (a) whether bacterial communities vary among host genotypes in the water flea Daphnia galeata and (b) if this difference is driven by the genetic distance between host genotypes, by using D. galeata genotypes hatched from sediments of different time periods. We used 16S amplicon sequencing to profile the gut and body bacterial communities of eight D. galeata genotypes hatched from resting eggs; these were isolated from two distinct sediment layers (dating to 1989 and 2009) of a single sediment core of the lake Greifensee, and maintained in a common garden in laboratory cultures for 5 years. In general, bacterial community composition varied in both the Daphnia guts and bodies; but not between genotypes from different sediment layers. Specifically, genetic distances between host genotypes did not correlate with beta diversity of bacterial communities in Daphnia guts and bodies. Our results indicate that Daphnia bacterial community structure is to some extent determined by a host genetic component, but that genetic distances between hosts do not correlate with diverging bacterial communities. [ABSTRACT FROM AUTHOR]

My goal in writing this is to increase awareness of the roles played by microbial symbionts in eukaryote ecology and evolution. Most eukaryotes host one or more species of symbiotic microorganisms, including prokaryotes and fungi. Many of these have profound impacts on the biology of their hosts. For example, microbial symbionts may expand the niches of their hosts, cause rapid adaptation of the host to the environment and re-adaptation to novel conditions via symbiont swapping, facilitate speciation, and fundamentally alter our concept of the species. In some cases, microbial symbionts and multicellular eukaryote hosts have a mutual dependency, which has obvious conservation implications. Hopefully, this contribution will stimulate a reevaluation of important ecological and evolutionary concepts including niche, adaptation, the species, speciation, and conservation of multicellular eukaryotes. [ABSTRACT FROM AUTHOR]

The epidermis of Chondrichthyan fishes consists of dermal denticles with production of minimal but protein-rich mucus that collectively, influence the attachment and biofilm development of microbes, facilitating a unique epidermal microbiome. Here, we use metagenomics to provide the taxonomic and functional characterization of the epidermal microbiome of the Triakis semifasciata (leopard shark) at three time-points collected across 4 years to identify links between microbial groups and host metabolism. Our aims include (1) describing the variation of microbiome taxa over time and identifying recurrent microbiome members (present across all time-points); (2) investigating the relationship between the recurrent and flexible taxa (those which are not found consistently across time-points); (3) describing the functional compositions of the microbiome which may suggest links with the host metabolism; and (4) identifying whether metabolic processes are shared across microbial genera or are unique to specific taxa. Microbial members of the microbiome showed high similarity between all individuals (Bray–Curtis similarity index = 82.7, where 0 = no overlap, 100 = total overlap) with the relative abundance of those members varying across sampling time-points, suggesting flexibility of taxa in the microbiome. One hundred and eighty-eight genera were identified as recurrent, including Pseudomonas, Erythrobacter, Alcanivorax, Marinobacter, and Sphingopxis being consistently abundant across time-points, while Limnobacter and Xyella exhibited switching patterns with high relative abundance in 2013, Sphingobium and Sphingomona in 2015, and Altermonas, Leeuwenhoekiella, Gramella, and Maribacter in 2017. Of the 188 genera identified as recurrent, the top 19 relatively abundant genera formed three recurrent groups. The microbiome also displayed high functional similarity between individuals (Bray–Curtis similarity index = 97.6) with gene function composition remaining consistent across all time-points. These results show that while the presence of microbial genera exhibits consistency across time-points, their abundances do fluctuate. Microbial functions however remain stable across time-points; thus, we suggest the leopard shark microbiomes exhibit functional redundancy. We show coexistence of microbes hosted in elasmobranch microbiomes that encode genes involved in utilizing nitrogen, but not fixing nitrogen, degrading urea, and resistant to heavy metal. [ABSTRACT FROM AUTHOR]

Environmental conditions change rapidly along elevational gradients and have been found to affect community composition in macroscopic taxa, with lower diversity typically observed at higher elevations. In contrast, microbial community responses to elevation are still poorly understood. Specifically, the effects of elevation on vector-associated microbiota have not been studied to date, even though the within-vector microbial community is known to influence vector competence for a range of zoonotic pathogens. Here we characterize the structure and diversity of the bacterial microbiota in an important zoonotic disease vector, the sheep tick Ixodes ricinus, along replicated elevational gradient (630–1673 m) in the Swiss Alps. 16S rRNA sequencing of the whole within-tick bacterial microbiota of questing nymphs and adults revealed a decrease in Faith's phylogenetic microbial alpha diversity with increasing elevation, while beta diversity analyses revealed a lower variation in microbial community composition at higher elevations. We also found a higher microbial diversity later in the season and significant differences in microbial diversity among tick life stages and sexes, with lowest microbial alpha diversity observed in adult females. No associations between tick genetic diversity and bacterial diversity were observed. Our study demonstrates systematic changes in tick bacterial microbiota diversity along elevational gradients. The observed patterns mirror diversity changes along elevational gradients typically observed in macroscopic taxa, and they highlight the key role of environmental factors in shaping within-host microbial communities in ectotherms. [ABSTRACT FROM AUTHOR]

As corals continue to decline globally, particularly due to climate change, it is vital to understand the extent to which their microbiome may confer an adaptive resilience against environmental stress. Corals that survive on the urban reefs of Singapore are ideal candidates to study the association of scleractinians with their microbiome, which in turn can inform reef conservation and management. In this study, we monitored differences in the microbiome of Pocillopora acuta colonies reciprocally transplanted between two reefs, Raffles and Kusu, within the Port of Singapore, where corals face intense anthropogenic impacts. Pocillopora acuta had previously been shown to host distinct microbial communities between these two reefs. Amplicon sequencing (16S rRNA) was used to assess the coral microbiomes at 1, 2, 4, and 10 days post-transplantation. Coral microbiomes responded rapidly to transplantation, becoming similar to those of the local corals at the destination reef within one day at Raffles and within two days at Kusu. Elevated nitrate concentrations were detected at Raffles for the duration of the study, potentially influencing the microbiome's response to transplantation. The persistence of corals within the port of Singapore highlights the ability of corals to adapt to stressful environments. Further, coral resilience appears to coincide with a dynamic microbiome which can undergo shifts in composition without succumbing to dysbiosis. [ABSTRACT FROM AUTHOR]

In this study, we hypothesized that sympatrically grown farmed fish, i.e. fish which experience similar environmental conditions and nutritionally similar diets, would have more convergent gut microbiota. Using a "common garden" approach, we identified the core microbiota and bacterial community structure differences between five fish species farmed in the same aquaculture site on the west coast of the Aegean Sea, Greece. The investigated individuals were at similar developmental stages and reared in adjacent (< 50 m) aquaculture cages; each cage had 15 kg fish m−3. The diets were nutritionally similar to support optimal growth for each fish species. DNA from the midgut of 3–6 individuals per fish species was extracted and sequenced for the V3–V4 region of the bacterial 16S rRNA. Only 3.9% of the total 181 operational taxonomic units (OTUs) were shared among all fish. Between 5 and 74 OTUs were unique to each fish species. Each of the investigated fish species had a distinct profile of dominant OTUs, i.e. cumulative relative abundance of ≥ 80%. Co-occurrence network analysis for each fish species showed that all networks were strongly dominated by positive correlations between the abundances of their OTUs. However, each fish species had different network characteristics suggesting the differential significance of the OTUs in each of the five fish species midgut. The results of the present study may provide evidence that adult fish farmed in the Mediterranean Sea have a rather divergent and species-specific gut microbiota profile, which are shaped independently of the similar environmental conditions under which they grow. [ABSTRACT FROM AUTHOR]

Coral-associated bacteria are critical for the well-being of their host and may play essential roles during ontogeny, as suggested by the vertical transmission of some bacteria in brooding corals. Bacterial acquisition patterns in broadcast spawners remain uncertain, as 16S rRNA gene metabarcoding of coral early life stages suggests the presence of bacterial communities, which have not been detected by microscopic examinations. Here, we combined 16S rRNA gene metabarcoding with fluorescence in situ hybridization (FISH) microscopy to analyze bacterial assemblages in Acropora tenuis egg–sperm bundles, embryos, and larvae following a spawning event. Metabarcoding results indicated that A. tenuis offspring ≤ 4-day-old were associated with diverse and dynamic bacterial microbiomes, dominated by Rhodobacteraceae, Alteromonadaceae, and Oceanospirillaceae. While FISH analyses confirmed the lack of internalized bacteria in A. tenuis offspring, metabarcoding showed that even the earliest life stages examined (egg–sperm bundles and two-cell stages) were associated with a diverse bacterial community, suggesting the bacteria were confined to the mucus layer. These results can be explained by vertical transmission of certain taxa (mainly Endozoicomonas) in the mucus surrounding the gametes within bundles, or by horizontal bacterial transmission through the release of bacteria by spawning adults into the water column. [ABSTRACT FROM AUTHOR]

The effect of short-term nutrient deprivation was studied in five populations of the mite Tyrophagus putrescentiae with different microbiomes. The fresh weight, nutrient status, respiration, and population growth of the mites were observed for the five mite population-scale samples. The starvation caused the larvae and nymphs to be eliminated, resulting in a significant increase in the fresh weight of starved adult specimens. Three populations were negatively influenced by starvation, and the starved specimens were characterized by a decrease in nutrient status, respiration, and population growth. One population was not influenced or was slightly influenced by starvation, which had no effect on population growth or nutrient contents but caused a significant decrease in respiration. One population was positively influenced by starvation; the population growth increased in starved specimens, and starvation had no effect on respiration. Although starvation altered the bacterial profiles of the microbiomes, these differences were much smaller than those between the populations. The bacterial profiles of Staphylococcus, Bacillus, Kocuria, Brevibacterium, and unidentified Micrococcaceae and Enterobacteriaceae increased in starved specimens, whereas those of Bartonella and Solitalea-like genera were reduced in the starved mite populations. The profiles of the intracellular symbiont Cardinium decreased in the starved specimens, and the Wolbachia profile changes were dependent on the mite population. In mite populations, when the symbionts were rare, their profiles varied stochastically. Correlations between changes in the profiles of the bacterial taxa and mite fitness parameters, including nutrient status (lipids, proteins, saccharides, and glycogen contents), mite population growth, and respiration, were observed. Although the microbiomes were resistant to the perturbations caused by nutrition deficiency, the responses of the mites differed in terms of their population growth, respiration, and nutrient status. [ABSTRACT FROM AUTHOR]

Bamboo specialization is one of the most extreme examples of convergent herbivory, yet it is unclear how this specific high-fiber diet might selectively shape the composition of the gut microbiome compared to host phylogeny. To address these questions, we used deep sequencing to investigate the nature and comparative impact of phylogenetic and dietary selection for specific gut microbial membership in three bamboo specialists—the bamboo lemur (Hapalemur griseus, Primates: Lemuridae), giant panda (Ailuropoda melanoleuca, Carnivora: Ursidae), and red panda (Ailurus fulgens, Carnivora: Musteloideadae), as well as two phylogenetic controls—the ringtail lemur (Lemur catta) and the Asian black bear (Ursus thibetanus). We detected significantly higher Shannon diversity in the bamboo lemur (10.029) compared to both the giant panda (8.256; p = 0.0001936) and the red panda (6.484; p = 0.0000029). We also detected significantly enriched bacterial taxa that distinguished each species. Our results complement previous work in finding that phylogeny predominantly governs high-level microbiome community structure. However, we also find that 48 low-abundance OTUs are shared among bamboo specialists, compared to only 8 OTUs shared by the bamboo lemur and its sister species, the ringtail lemur (Lemur catta, a generalist). Our results suggest that deep sequencing is necessary to detect low-abundance bacterial OTUs, which may be specifically adapted to a high-fiber diet. These findings provide a more comprehensive framework for understanding the evolution and ecology of the microbiome as well as the host. [ABSTRACT FROM AUTHOR]