Triclosan exposure design.

<p>A schematic diagram of the experimental groups and triclosan exposures. Labeled tick marks represent days.</p

Triclosan Exposure Is Associated with Rapid Restructuring of the Microbiome in Adult Zebrafish

<div><p>Growing evidence indicates that disrupting the microbial community that comprises the intestinal tract, known as the gut microbiome, can contribute to the development or severity of disease. As a result, it is important to discern the agents responsible for microbiome disruption. While animals are frequently exposed to a diverse array of environmental chemicals, little is known about their effects on gut microbiome stability and structure. Here, we demonstrate how zebrafish can be used to glean insight into the effects of environmental chemical exposure on the structure and ecological dynamics of the gut microbiome. Specifically, we exposed forty-five adult zebrafish to triclosan-laden food for four or seven days or a control diet, and analyzed their microbial communities using 16S rRNA amplicon sequencing. Triclosan exposure was associated with rapid shifts in microbiome structure and diversity. We find evidence that several operational taxonomic units (OTUs) associated with the family Enterobacteriaceae appear to be susceptible to triclosan exposure, while OTUs associated with the genus <i>Pseudomonas</i> appeared to be more resilient and resistant to exposure. We also found that triclosan exposure is associated with topological alterations to microbial interaction networks and results in an overall increase in the number of negative interactions per microbe in these networks. Together these data indicate that triclosan exposure results in altered composition and ecological dynamics of microbial communities in the gut. Our work demonstrates that because zebrafish afford rapid and inexpensive interrogation of a large number of individuals, it is a useful experimental system for the discovery of the gut microbiome’s interaction with environmental chemicals.</p></div

Triclosan exposure is associated with alterations in microbial correlation networks.

<p>Interaction networks for microbial communities in (A) unexposed, (B) four-day exposure and (C) seven-day exposure groups. Network communities (subgraphs) are identified by colored polygons and the vertices (OTUs) that comprise these communities are colored identically to indicate network community membership. Each line represents an abundance correlation between two OTUs. The size of each vertex is proportional to its degree. Edges between different network communities are colored red and those within a community are black. (D) Venn diagram of shared vertices between networks. (E) Degree and (F) betweenness centrality distribution for all vertices in network. *** p < 0.001.</p

Triclosan exposure is associated with altered microbial community structure.

<p>(A) Phyla level taxa plot of the most abundant taxa in zebrafish gut microbiomes across exposure groups. (B) Non-metric multidimensional scaling analysis of unexposed (red dots), four-day (blue dots) and seven-day (green dots) exposure group’s microbial communities. Colored ellipses represent the 99.9% confidence interval for standard error of each group. (C) Comparisons of within group Bray-Curtis dissimilarity between groups. (D) Shannon entropy between exposure groups. Significant p-values (p < 0.05) are denoted with an asterisk.</p

Triclosan exposure is associated with unique indicator OTUs.

<p>Indicator values for significant (p < 0.05, q < 0.20) indicator taxa in (A) unexposed and (B) triclosan exposed fish. The size of each point is proportional to its class-wide relative abundance, and its color is proportional to its class-wide frequency.</p

Triclosan exposure is associated with significant alterations in OTU abundance.

<p>Fold change values for OTUs that were significantly altered in abundance in the (A) four-day, and (B) seven day exposure groups. Genus level taxonomic assignments are provided and corresponding OTU IDs indicated inside parentheses.</p