Responses of diverse gut microbiota affect the host's nutrient metabolism and disease immunity. However, giant pandas (Ailuropoda melanoleuca) have a low diversity of gut microbiota, and the reasons for this low diversity and its impact are poorly understood. In this study, we aimed to investigate the effects of diet on the diversity of gut microbiota in giant pandas. To analyze the functional genes of the gut microbiota, we employed PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states), a computational method for predicting the functional composition of genomes. A multispecies comparison was conducted, involving 66 individuals from 34 species including giant panda. Our comparative analysis revealed that a high-fiber diet significantly reduced the diversity of gut microbiota in giant pandas. Furthermore, we observed that the metabolic function of giant pandas, particularly in terms of energy families and amino acid metabolism, was significantly lower than in other species. During the high-fiber diet, the gut microbiota of giant pandas exhibited a greater abundance of genes involved in carbohydrate metabolism, amino acid metabolism, and transport functions. These findings suggest that a high-fiber bamboo (Poaceae) diet is associated with lower diversity and altered metabolic function of gut microbiota in giant pandas. Therefore, the gut microbiota of giant pandas undergoes functional adaptive changes in response to the consumption of a high-fiber bamboo diet.

The gut microbiota plays an important role in host nutrient absorption, immune function, and behavioral patterns. Much research on the gut microbiota of wildlife has focused on feces samples, so the microbial composition along the gastrointestinal tract of wildlife is not well reported. To address this gap, we performed high-throughput sequencing of 16s rRNA genes and ITs rRNA genes in the gastrointestinal contents of a wild adult male Chinese muntjac (Muntiacus reevesi) to comparatively analyze the microbial diversity of different gastrointestinal regions. The results showed that the dominant bacterial phyla were Firmicutes (66.19%) and Bacteroidetes (22.7%), while the dominant fungal phyla were Ascomycetes (72.81%). The highest bacterial diversity was found in the stomach, and the highest fungal diversity was found in the cecum. The microbial communities of the large intestine and small intestine were of similar structures, which were distinct from that of the stomach. These results would facilitate the continued exploration of the microbial composition and functional diversity of the gastrointestinal tract of wild Chinese muntjacs and provide a scientific basis for microbial resource conservation of more wildlife.

Nickel is a widespread ubiquitous environmental contaminant whose short-term impacts on the gut microbiota-metabolite-immune axis remains poorly defined. In this study, mice were exposed to nickel chloride every alternate day for 15 days via gavage, intraperitoneal injection, or nasal drop. Subsequently, the microbial, metabolic, and immunological responses were assessed. Additionally, 16S rRNA sequencing revealed route-dependent dysbiosis, characterized by the depletion of commensal taxa such as Prevotellaceae UCG-001, Rikenellaceae_RC9, and Alistipes, as well as the enrichment of opportunistic bacteria, including Helicobacter, Enterobacter, and Alloprevotella, particularly in the gavage and intraperitoneal groups. Functional predictions (PICRUSt2) indicated enrichment of immune-related pathways-notably, NOD-like receptor signalling, Th17 cell differentiation, and MAPK (Mitogen-Activated Protein Kinase) signalling-thereby implicating innate and adaptive inflammatory responses. Targeted metabolomics revealed significant elevations of acetate and propionate in the gavage and intraperitoneal groups, whereas butyrate displayed a transient increase associated with Clostridium sensu stricto 1 enrichment. In contrast, administration of nasal drops reduced isobutyrate and isovalerate, suggesting impaired proteolytic fermentation. Despite the increase in short-chain fatty acids (SCFAs), serum tumour necrosis factor-α (TNF-α) levels were significantly elevated, which was consistent with an overriding pro-inflammatory drive. These findings demonstrate that acute nickel exposure perturbs the gut microbiota and alters SCFA metabolism in a route-dependent manner. Concurrently, functional predictions and inflammatory readouts suggest engagement of the NOD-MAPK-Th17 axes. Consequently, this study highlights the complex interplay between microbial adaptation and host inflammation under acute heavy metal stress.