Seasonal and Regional Dynamics of the Intestinal Microbiota in Schizothorax nukiangensis from the Nujiang River

The dynamic alterations in intestinal microbiota can provide insights into the adaptive relationships between these microorganisms and their hosts in response to environmental changes. <i>Schizothorax nukiangensis</i> is widely distributed throughout the Nujiang River and exhibits numerous unique adaptations. In this study, we collected samples of <i>S. nukiangensis</i> across different seasons and regions within the Nujiang River to comprehensively elucidate the diversity and composition of its intestinal microbiota using metagenomic technology. The results indicated that Firmicutes and Proteobacteria predominated at the phylum level, while <i>Priestia</i>, <i>Bacillus</i>, and <i>Aeromonas</i> were the most abundant genera identified. Notably, the relative abundance of these microorganisms varied significantly across different seasons and regions. From autumn through spring and into summer, the predominant microorganisms shifted from Firmicutes to Proteobacteria. Biomarker analysis revealed that Firmicutes (including the class bacilli and the genera <i>Priestia</i> and <i>Bacillus</i>) exhibited a higher relative abundance within the upstream group, where categories related to amino acid metabolism and carbohydrate metabolism were significantly enriched. Conversely, Proteobacteria (including several potential pathogens, such as <i>Saezia</i>, <i>Pantoea</i>, <i>Lelliotia</i>, and <i>Aeromonas</i> genera) showed an increased relative abundance within downstream groups, where disease-related categories exhibited significant enrichment. Our findings significantly enhance our understanding of how <i>S. nukiangensis</i> adapts to its environment, providing valuable data support for the conservation of <i>S. nukiangensis</i> and for ecological security assessment of the Nujiang River.