Fecal transplants in zebrafish reveal effects of diet and microbiome on intestinal gene expression and enzyme activity.

This study examined the functional response of a host (zebrafish) to implantation of a conspecific or allospecific (goldfish) gastrointestinal (GIT) microbiome followed by diet manipulation and the repercussions of these manipulations on host GIT physiology. Implantation of a native zebrafish biome successfully reintroduced wildtype (WT) communities with the exception of several rare, phylogenetically distant species. Implantation of a foreign goldfish biome created communities that were distinct from WT, suggesting that the seeding community created substantial differences from the native host communities. A mismatched ?natural? diet and an implanted allospecific biome enriched for rarer and more phylogenetically diverse bacteria. Transcriptional changes within the GIT clustered in relationship to biome treatments, mirroring clustering of biome implants. Implantation of an allospecific biome along with an altered diet markedly down-regulated approximately 70% of the transcripts involved in cholesterol biosynthesis, while tissue content analysis revealed an increase in total tissue cholesterol. Furthermore, transcripts involved in lipogenesis pathways were significantly downregulated and correlated with a striking decrease in intestinal lipase activity driven by both biome and diet. Glucose-6P dehydrogenase (G6PD) activities increased during dietary manipulations regardless of biome, while the allospecific biome down-regulated transcripts involved in gluconeogenesis and altered glucokinase (GK) and hexokinase (HK) activities regardless of diet. However, growth rates did not reveal an impact of these responses. Adult zebrafish are unable to reform proportional representation within bacterial communities following transplantation of an allospecific biome resulting in transcriptional and enzymatic alterations for lipid and carbohydrate metabolism that did not affect overall animal homeostasis. The intestinal microbiome of zebrafish was manipulated either through removal and reintroduction or through removal and introduction of another specie's intestinal microbiome (goldfish). The diet was also manipulated, either maintaining the original zebrafish diet or switching to a goldfish diet.