Effects of thallium exposure on intestinal microbial community and organ functions in Zebrafish (Danio rerio)

Thallium (Tl) is a highly toxic trace metal widely distributed in water environments,which may threaten the water quality and aquatic organisms at an excessive level dueto increased anthropogenic activities. This study investigated the changes inmicrobiota communities of intestine and organs of zebrafish, toxic responseassessment including intestinal microbiota composition and the histopathology of gilland liver tissues under exposure of Tl at environmental-relevant levels. Theresults supported that the intestinal microbial community of zebrafish greatly changedunder a relatively high Tl concentration (1000 ng/L). A significant increase ofpathogenic intestinal bacteria such as Mycobaterium in intestine of zebrafish exposedat Tl levels over 500 ng/L was found. Additionally, gill and liver tissues displayeddifferent degrees of damage under Tl exposure, which possibly leads to matingbehaviors change and death of zebrafish. The overall results indicated that lowdoses of Tl in the aquatic environment induce highly toxicity to zebrafish and may posepathological threats to the gill, liver, with the changing of community structure ofintestinal microorganisms.