A Comparative Study on the Faecal Bacterial Community and Potential Zoonotic Bacteria of Muskoxen (Ovibos moschatus) in Northeast Greenland, Northwest Greenland and Norway

Metabarcoding of fecal pellets in wild muskox populations reveals negative relationships between microbiome and diet alpha diversity

Microbiome diversity and diet composition concomitantly influence species health, fitness, immunity, and digestion. In environments where diet varies spatially and temporally, microbiome plasticity may promote rapid host adaptation to available resources. For northern ungulates in particular, metabarcoding of noninvasively collected fecal pellets presents unprecedented insights into their diverse ecological requirements and niches by clarifying the interrelationships of microbiomes, key to deriving nutrients, in context of altered forage availability in changing climates. Muskoxen (Ovibos moschatus) are Arctic-adapted species that experience fluctuating qualities and quantities of vegetation. Geography and seasonality have been noted to influence microbiome composition and diversity in muskoxen, yet it is unclear how their microbiomes intersect with diet. Following observations from other species, we hypothesized increasing diet diversity would result in higher microbiome diversity in muskoxen. We assessed diet composition in muskoxen using three common plant metabarcoding markers and explored correlations with microbiome data. Patterns of dietary diversity and composition were not fully concordant among the markers used, yet all reflected the primary consumption of willows and sedges. Individuals with similar diets had more similar microbiomes, yet in contrast to most literature, yielded negative relationships between microbiome and diet alpha diversity. This negative correlation may reflect the unique capacities of muskoxen to survive solely on high-fiber Arctic forage and provide insight into their resiliency to exploit changing dietary resources in a rapidly warming Arctic altering vegetation diversity.

High-Altitude Drives the Convergent Evolution of Alpha Diversity and Indicator Microbiota in the Gut Microbiomes of Ungulates

Convergent evolution is an important sector of evolutionary biology. High-altitude environments are one of the extreme environments for animals, especially in the Qinghai Tibet Plateau, driving the inquiry of whether, under broader phylogeny, high-altitude factors drive the convergent evolution of Artiodactyla and Perissodactyla gut microbiomes. Therefore, we profiled the gut microbiome of Artiodactyla and Perissodactyla at high and low altitudes using 16S rRNA gene sequencing. According to cluster analyses, the gut microbiome compositions of high-altitude Artiodactyla and Perissodactyla were not grouped together and were far from those of low-altitude Artiodactyla and Perissodactyla. The Wilcoxon’s test in high-altitude ungulates showed significantly higher Sobs and Shannon indices than in low-altitude ungulates. At the phylum level, Firmicutes and Patescibacteria were significantly enriched in the gut microbiomes of high-altitude ungulates, which also displayed a higher Firmicutes/Bacteroidetes value than low-altitude ungulates. At the family level, Ruminococcaceae, Christensenellaceae, and Saccharimonadaceae were significantly enriched in the gut microbiomes of high-altitude ungulates. Our results also indicated that the OH and FH groups shared two significantly enriched genera, Christensenellaceae_R_7_group and Candidatus_Saccharimonas. These findings indicated that a high altitude cannot surpass the order level to drive the convergent evolution of ungulate gut microbiome composition but can drive the convergent evolution of alpha diversity and indicator microbiota in the gut microbiome of ungulates. Overall, this study provides a novel perspective for understanding the adaptation of ungulates to high-altitude environments.

Muskoxen homogenise soil microbial communities and affect the abundance of methanogens and methanotrophs

Grazing herbivores may affect soil microbial communities indirectly by impacting soil structure and vegetation composition. In high arctic environments, this impact is poorly elucidated, while having potentially wide-reaching effects on the ecosystem. This study examines how a key arctic herbivore, the muskox Ovibos moschatus, affects the soil microbial community in a high arctic fen. Environmental DNA was extracted from soil samples taken from grazed control plots and from muskox exclosures established 5 years prior. We sequenced amplicons of the 16S rRNA gene to provide insight into the microbial communities. We found that in the grazed control plots, microbial communities exhibited high evenness and displayed highly similar overall diversity. In plots where muskoxen had been excluded, microbial diversity was significantly reduced, and had more uneven intra-sample populations and overall lower ecological richness and evenness. We observed that the composition of microbial communities in grazed soils were significantly affected by the presence of muskoxen, as seen by elevated relative abundances of Bacteroides and Firmicutes, two major phyla found in muskox faeces. Furthermore, an increase in relative abundance of bacteria involved in degradation of recalcitrant carbohydrates and cycling of nitrogen was observed in grazed soil. Ungrazed soils displayed increased abundances of bacteria potentially involved in anaerobic oxidation of methane, whereas some methanogens were more abundant in grazed soils. This corroborates a previous finding that methane emissions are higher in arctic fens under muskox grazing. Our results show that the presence of large herbivores stimulates soil microbial diversity and has a homogenizing influence on the inter-species dynamics in soil microbial communities. The findings of this study, thus, improve our understanding of the effect of herbivore grazing on arctic ecosystems and the derived methane cycling.

Fecal microbiota and diets of muskox female adults and calves

In mammals, the gut microbiome is vertically transmitted during maternal lactation at birth. In this study, we investigated the gut microbiome and diets of muskox, a large herbivore inhabiting in the high Arctic. We compared the microbiota composition using bacterial 16S rRNA gene sequencing and diets using stable isotope analysis of muskox feces of six female adults and four calves on Ella Island, East Greenland. Firmicutes were the most abundant bacterial phylum in both the adults and calves, comprising 94.36% and 94.03%, respectively. Significant differences were observed in the relative abundance of the two Firmicutes families. The adults were primarily dominated by Ruminococcaceae (73.90%), and the calves were dominated by both Ruminococcaceae (56.25%) and Lachnospiraceae (24.00%). Stable isotope analysis of the feces in the study area revealed that both adults and calves had similar ranges of ¹³C and ¹⁵N, likely derived from the dominant diet plants. Despite their similar diets, the different gut microbiome compositions in muskox adults and calves indicate that the gut microbiome of the calves may not be fully colonized to the extent of that of the adults.

Zoonotic pathogens in wild muskoxen (Ovibos moschatus) and domestic sheep (Ovis aries) from Greenland

The present study aimed to estimate the prevalence of zoonotic pathogens Giardia duodenalis, Cryptosporidium spp., Toxoplasma gondii and Erysipelothrix in muskoxen (Ovibos moschatus) and sheep (Ovis aries) from Greenland. In 2017 and 2018, faecal samples were collected from wild muskoxen from three distinct populations (Zackenberg, Kangerlussuaq, and Ivittuut) and from domestic sheep from southwest Greenland. Blood samples were collected from muskoxen from Kangerlussuaq and Ivittuut and from sheep. Faecal samples were tested for specific DNA of G. duodenalis and Cryptosporidium spp., and blood samples were tested for antibodies against T. gondii and Erysipelothrix. The estimated prevalence of G. duodenalis was 0% (0/58), 17% (7/41) and 0% (0/55) in muskoxen from Zackenberg, Kangerlussuaq and Ivittuut, respectively, and 37% (16/43) in sheep. The estimated prevalence of Cryptosporidium was 0% (0/58), 2% (1/41), 7% (4/55) in muskoxen from Zackenberg, Kangerlussuaq, Ivittuut, respectively, and 2% (1/43) in sheep. Neither Giardia nor Cryptosporidium were detected in winter samples (0/78). Of the positive samples, Giardia from one muskox sample only was successfully typed as G. duodenalis assemblage A, and Cryptosporidium from two muskoxen was successfully typed as C. parvum, subtype IIdA20G1e. The estimated T. gondii seroprevalence was 2% (1/44) and 0% (0/8) in muskoxen from Kangerlussuaq and Ivittuut, respectively, and 1% (1/155) in sheep. The estimated Erysipelothrix seroprevalence was 2% (1/45) and 13% (1/8) in muskoxen from Kangerlussuaq and Ivittuut, respectively, and 7% (10/150) in sheep. The results of this study add to the scarce knowledge on zoonotic pathogens in the Arctic.

Geography, seasonality, and host-associated population structure influence the fecal microbiome of a genetically depauparate Arctic mammal

The Canadian Arctic is an extreme environment with low floral and faunal diversity characterized by major seasonal shifts in temperature, moisture, and daylight. Muskoxen (Ovibos moschatus) are one of few large herbivores able to survive this harsh environment. Microbiome research of the gastrointestinal tract may hold clues as to how muskoxen exist in the Arctic, but also how this species may respond to rapid environmental changes. In this study, we investigated the effects of season (spring/summer/winter), year (2007-2016), and host genetic structure on population-level microbiome variation in muskoxen from the Canadian Arctic. We utilized 16S rRNA gene sequencing to characterize the fecal microbial communities of 78 male muskoxen encompassing two population genetic clusters. These clusters are defined by Arctic Mainland and Island populations, including the following: (a) two mainland sampling locations of the Northwest Territories and Nunavut and (b) four locations of Victoria Island. Between these geographic populations, we found that differences in the microbiome reflected host-associated genetic cluster with evidence of migration. Within populations, seasonality influenced bacterial diversity with no significant differences between years of sampling. We found evidence of pathogenic bacteria, with significantly higher presence in mainland samples. Our findings demonstrate the effects of seasonality and the role of host population-level structure in driving fecal microbiome differences in a large Arctic mammal.

Influence of Season and Diet on Fiber Digestion and Bacterial Community Structure in the Rumen of Muskoxen (Ovibos moschatus)

We studied the relationship between fiber digestion and the composition of the bacterial community in the rumen of muskoxen at the start and the end of the annual window of plant growth from spring to fall. Eight ruminally cannulated castrated males were fed brome hay or triticale straw (69.6% vs. 84.6% neutral detergent fiber, respectively) that were similar in fiber content to the sedges consumed by wild muskoxen (64.5 to 71.7% neutral detergent fiber). Muskoxen digested fiber from both forages faster and to a greater extent when straw rather than hay was consumed. Fiber digestion was therefore inducible by diet 4 in each season. We used 16S rRNA sequences from ruminal contents to study how season and diet affected the bacterial community and how the latter related to fiber digestion. We found that Bacteroidetes and Firmicutes accounted for 90% of the sequences at the level of Phylum, which is typical for the mammal gut microbiome. Using partial least square regressions, it was found that between 48% and 72% of the variation in fiber digestion was associated with 36–43 genera of bacteria. The main fibrolytic bacteria typical of domestic ruminants were generally not among the most important bacteria associated with fiber digestion in muskoxen. This reveals that muskoxen rely upon on a large suite of bacterial genera that are largely distinct from those used by other ruminants to digest the cell walls of plants that vary widely in both abundance and nutritional quality through the year.