Dysbiosis of Gut Microbiome Aggravated Male Infertility in Captivity of Plateau Pika.

Captivity is an important and efficient technique for rescuing endangered species. However, it induces infertility, and the underlying mechanism remains obscure. This study used the plateau pika (Ochotona curzoniae) as a model to integrate physiological, metagenomic, metabolomic, and transcriptome analyses and explore whether dysbiosis of the gut microbiota induced by artificial food exacerbates infertility in captive wild animals. Results revealed that captivity significantly decreased testosterone levels and the testicle weight/body weight ratio. RNA sequencing revealed abnormal gene expression profiles in the testicles of captive animals. The microbial α-diversity and Firmicutes/Bacteroidetes ratio were drastically decreased in the captivity group. Bacteroidetes and Muribaculaceae abundance notably increased in captive pikas. Metagenomic analysis revealed that the alteration of flora increased the capacity for carbohydrate degradation in captivity. The levels of microbe metabolites' short-chain fatty acids (SCFAs) were significantly high in the captive group. Increasing SCFAs influenced the immune response of captivity plateau pikas; pro-inflammatory cytokines were upregulated in captivity. The inflammation ultimately contributed to male infertility. In addition, a positive correlation was observed between Gastranaerophilales family abundance and testosterone concentration. Our results provide evidence for the interactions between artificial food, the gut microbiota, and male infertility in pikas and benefit the application of gut microbiota interference in threatened and endangered species.

Plant Secondary Compounds Promote White Adipose Tissue Browning via Modulation of the Gut Microbiota in Small Mammals.

The browning of white adipose tissue (WAT) is a promising area of research for treating metabolic disorders and obesity in the future. However, studies on plant secondary compounds promoting WAT browning are limited. Herein, we explored the effects of swainsonine (SW) on gut microbiota and WAT browning in captive pikas. SW inhibited body mass gain, increased brown adipose tissue (BAT) mass, and induced WAT browning in pikas. The 16S rDNA sequencing revealed a significant reduction in the alpha diversity and altered community structure of the gut microbiota in captive pikas. However, the addition of SW to the diet significantly increased the alpha diversity of gut microbiota and the relative abundance of Akkermansia, Prevotella, and unclassified_f__Lachnospiraceae, along with the complexity of the microbial co-occurrence network structure, which decreased in the guts of captive pikas. Functional profiles showed that SW significantly decreased the relative abundances of energy metabolism, lipid metabolism, and glycan biosynthesis and metabolism, which were enriched in captive pikas. Furthermore, SW decreased deterministic processes of gut microbiota assembly in July and increased them in November. Finally, the genera Prevotella and unclassified_f__Prevotellaceae were positively correlated with BAT mass. Our results highlighted that plant secondary compounds promote WAT browning by modulating the gut microbiota in small mammals.

Stochastic Processes Derive Gut Fungi Community Assembly of Plateau Pikas (Ochotona curzoniae) along Altitudinal Gradients across Warm and Cold Seasons.

Although fungi occupy only a small proportion of the microbial community in the intestinal tract of mammals, they play important roles in host fat accumulation, nutrition metabolism, metabolic health, and immune development. Here, we investigated the dynamics and assembly of gut fungal communities in plateau pikas inhabiting six altitudinal gradients across warm and cold seasons. We found that the relative abundances of Podospora and Sporormiella significantly decreased with altitudinal gradients in the warm season, whereas the relative abundance of Sarocladium significantly increased. Alpha diversity significantly decreased with increasing altitudinal gradient in the warm and cold seasons. Distance-decay analysis showed that fungal community similarities were significantly and negatively correlated with elevation. The co-occurrence network complexity significantly decreased along the altitudinal gradients as the total number of nodes, number of edges, and degree of nodes significantly decreased. Both the null and neutral model analyses showed that stochastic or neutral processes dominated the gut fungal community assembly in both seasons and that ecological drift was the main ecological process explaining the variation in the gut fungal community across different plateau pikas. Homogeneous selection played a weak role in structuring gut fungal community assembly during the warm season. Collectively, these results expand our understanding of the distribution patterns of gut fungal communities and elucidate the mechanisms that maintain fungal diversity in the gut ecosystems of small mammals.

Temporal and geographic distribution of gut microbial enterotypes associated with host thermogenesis characteristics in plateau pikas.

IMPORTANCE: The gut microbiotas of small mammals play an important role in host energy homeostasis. However, it is still unknown whether small mammals with different enterotypes show differences in thermogenesis characteristics. Our study confirmed that plateau pikas with different bacterial enterotypes harbored distinct thermogenesis capabilities and employed various strategies against cold environments. Additionally, we also found that pikas with different fungal enterotypes may display differences in coprophagy.

Dietary Fiber Influences Bacterial Community Assembly Processes in the Gut Microbiota of Durco × Bamei Crossbred Pig.

Several studies have shown that dietary fiber can significantly alter the composition and structure of the gut bacterial community in humans and mammals. However, few researches have been conducted on the dynamics of the bacterial community assembly across different graded levels of dietary fiber in different gut regions. To address this, 24 Durco × Bamei crossbred pigs were randomly assigned to four experimental chows comprising graded levels of dietary fiber. Results showed that the α-and ß-diversity of the bacterial community was significantly different between the cecum and the jejunum. Adding fiber to the chow significantly increased the α-diversity of the bacterial community in the jejunum and cecum, while the ß-diversity decreased. The complexity of the bacterial network increased with the increase of dietary fiber in jejunal content samples, while it decreased in cecal content samples. Furthermore, we found that stochastic processes governed the bacterial community assembly of low and medium dietary fiber groups of jejunal content samples, while deterministic processes dominated the high fiber group. In addition, deterministic processes dominated all cecal content samples. Taken together, the variation of gut community composition and structure in response to dietary fiber was distinct in different gut regions, and the dynamics of bacterial community assembly across the graded levels of dietary fiber in different gut regions was also distinct. These findings enhanced our knowledge on the bacterial community assembly processes in gut ecosystems of livestock.

The plant secondary compound swainsonine reshapes gut microbiota in plateau pikas (Ochotona curzoniae).

Plants produce various plant secondary compounds (PSCs) to deter the foraging of herbivorous mammals. However, little is known about whether PSCs can reshape gut microbiota and promote gut homeostasis of hosts. Using 16S rDNA sequencing to investigate the effects of PSCs on the gut microbiota of small herbivorous mammals, we studied plateau pikas (Ochotona curzoniae) fed diets containing swainsonine (SW) extracted from Oxytropis ochrocephala. Our results showed that both long- and short-term treatment of a single artificial diet in the laboratory significantly reduced alpha diversity and significantly affected beta diversity, core bacteria abundance, and bacterial functions in pikas. After SW was added to the artificial diet, the alpha diversity significantly increased in the long-term treatment, and core bacteria (e.g., Akkermansiaceae) with altered relative abundances in the two treatments showed no significant difference compared with pikas in the wild. The complexity of the co-occurrence network structure was reduced in the artificial diet, but it increased after SW was added in both treatments. Further, the abundances of bacteria related to altered alanine, aspartate, and glutamate metabolism in the artificial diet were restored in response to SW. SW further decreased the concentration of short-chain fatty acids (SCFAs) in both treatments. Our results suggest that PSCs play a key role in regulating gut microbiota community and intestinal homeostasis, thereby maintaining host health. KEY POINTS: • Swainsonine improves the intestinal bacterial diversity of plateau pikas. • Swainsonine promotes the recovery of core bacterial abundances in the gut of plateau pikas. • Swainsonine promotes the restoration of intestinal bacterial functions of plateau pikas.

Gastrointestinal Tract and Dietary Fiber Driven Alterations of Gut Microbiota and Metabolites in Durco × Bamei Crossbred Pigs.

Gastrointestinal tract and dietary fiber (DF) are known to influence gut microbiome composition. However, the combined effect of gut segment and long-term intake of a high fiber diet on pig gut microbiota and metabolite profiles is unclear. Here, we applied 16S rRNA gene sequencing and untargeted metabolomics to investigate the effect of broad bean silage on the composition and metabolites of the cecal and jejunal microbiome in Durco × Bamei crossbred pigs. Twenty-four pigs were allotted to four graded levels of DF chow, and the content of jejunum and cecum were collected. Our results demonstrated that cecum possessed higher α-diversity and abundance of Bacteroidetes, unidentified Ruminococcaceae compared to jejunum, while jejunum possessed higher abundance of Lactobacillus, Streptococcus. DF intake significantly altered diversity of the bacterial community. The abundance of Bacteroidetes and Turicibacter increased with the increase of DF in cecum and jejunum respectively. Higher concentrations of amino acids and conjugated bile acids were detected in the jejunum, whereas free bile acids and fatty acids were enriched in the cecum. The concentrations of fatty acids, carbohydrate metabolites, organic acids, 2-oxoadipic acid, and succinate in cecum were higher in the high DF groups. Overall, the results indicate that the composition of bacteria and the microbiota metabolites were distinct in different gut segments. DF had a significant influence on the bacterial composition and structure in the cecum and jejunum, and that the cecal metabolites may further affect host health, growth, and slaughter performance.

Taxonomy and phylogenetic relationship of zokors.

Zokor (Myospalacinae) is one of the subterranean rodents, endemic to east Asia. Due to the convergent and parallel evolution induced by its special lifestyles, the controversies in morphological classification of zokor appeared at the level of family and genus. To resolve these controversies about taxonomy and phylogeny, the phylogenetic relationships of 20 species of Muroidea and six species of zokors were studied based on complete mitochondrial genome and mitochondrial Cytb gene, respectively. Phylogeny analysis of 20 species of Muroidea indicated that the zokor belonged to the family Spalacidae, and it was closer to mole rat rather than bamboo rat. Besides, by investigating the phylogenetic relationships of six species of zokors, the status of two genera of Eospalax and Myospalax was affirmed because the two clades differentiated in phylogenetic tree represented two types of zokors, convex occiput type and flat occiput type, respectively. In addition, the two origins in Eospalax were found diverged at 3.71 million years ago (Ma) based on estimation of divergence time. It is suggested that the climate and ecology changes caused by the Qinghai-Tibet Plateau uplift event in 3.6 Ma led to the inner divergence of Eospalax. The intraspecific phylogenetic relationships of partial zokors were well resolved, the two clades of Eospalax cansus represented two geographical populations, respectively, and the divergent pattern of Eospalax baileyi was characterized by allopatric divergence spatially. In this study, we explored the taxonomic status and phylogenetic relationships of Myospalacinae at the molecular level. These works would be significant to understanding the evolutionary process and to clarify the mechanism of differentiation of Myospalacinae.