Effect of Silver Nanoparticles on Gut Microbiota Composition of Striped Dwarf Catfish (Mystus vittatus): A Metagenomic Analysis

This study was initiated to investigate the impact of dietary silver nanoparticles (AgNPs) on the gut microbiota of Mystus vittatus using metagenomic analysis. Fish were fed a regular diet and an AgNPs-supplemented diet (50 mg/kg) for 75 days, and the gut content was collected for microbial profiling using short-read sequencing of the hypervariable V3-V4 region of the 16S rRNA gene. The sequencing results identified 18 phyla, 25 classes, 67 orders, 92 families, and 107 genera, clustering into 361 amplicon sequence variants (ASVs). Fish in the AgNPs-fed group showed higher microbial richness, diversity, and evenness, as indicated by increased Chao1 and Shannon index values, whereas Simpson`s dominance index was lower. However, both alpha and beta diversity showed no significant difference (P>0.05). Taxonomic analysis revealed Proteobacteria, Fusobacteriota, and Firmicutes as the dominant phyla in both groups. Particularly, the AgNPs-fed fish showed an increased abundance of Bacillus, suggesting a potential probiotic-promoting effect of AgNPs. Moreover, the exclusive presence of Ralstonia and Candidatus Arthromitus in the AgNPs group was identified as potential genus-based biomarkers. These results indicate that dietary AgNPs influence gut microbiota in M. vittatus, with potential benefits for fish health and aquaculture nutrition.