Short-term triphenyltin exposure alters microbial homeostasis in the silkworm ( Bombyx mori ) midgut

Triphenyltin (TPT) is a widespread synthetic chemical used in many fields and its potential risk to organisms has been comprehensively investigated using different animal models and species. Currently, little is known about the effects of TPT exposure on microbial midgut diversity, therefore we explored these effects in the lepidopterous silkworm model using 16S rDNA sequencing. In total, 5273 and 5065 operational taxonomic units (OTUs) were identified in control and TPT-exposure group samples, ranging from 424 to 728 OTUs/sample. Alpha-diversity analyses revealed that TPT exposure induced the fluctuations of gut microbial diversity and abundance while beta-diversity analyses identified a distinct impact on major gut microbiota components. In our microbiome analyses, 23 phyla and 353 genera were recognized in the control group, while 20 phyla and 358 genera were recognized in the TPT exposure group. At the genus level, midgut microbiota were composed of several predominant bacterial genera, including Muribaculaceae, Lactobacillus, and UCG-010 . In the TPT exposure group, o__Bacillales, f__Bacillaceae, and f__Caldicoprobacteraceae abundance was relatively high, while f__Oscillospiraceae, f__Fusobacteriaceae, and f__SC_I_84 abundance was relatively high in the control group. Gene function analyses in silkworm microbiota after TPT exposure showed that biosynthesis of ansamycins, fructose and mannose metabolism, glycerolipid metabolism, type II diabetes mellitus, glycolysis/gluconeogenesis, lipid metabolism, translation proteins, atrazine degradation, DNA repair and recombination proteins, nicotinate and nicotinamide metabolism were significantly increased. Collectively, our silkworm model identified gut microbial diversity risks and the adverse effects from TPT exposure, which were similar to other aquatic animals. Therefore, TPT levels in environmental samples must be monitored to prevent ecological harm.