Dysbiosis of gut microbiota by actual long-term exposure to textile wastewater treatment plant effluents in adult zebrafish (Danio rerio) using aquatic microcosm systems

In the future, textile industry wastewater may create greater possibilities of releasing emerging contaminants into aquatic environments. Research on textile dyeing wastewater has focused on its adverse effects on biota. However, the effects of textile wastewater on gut microbiome and host health have not yet been elucidated, especially for the toxic assessment of combined pollutants under receiving water environment conditions. During this study, adult zebrafish were exposed to realistic textile wastewater treatment plant (TWTP) effluents in aquatic microcosm systems (AMS) for six months, a histopathological examination was performed, after which 16S rRNA and metagenomic sequencing of the intestinal microbiota was conducted and fish growth performance was also examined. As a result of exposure to TWTP effluents, adult zebrafish growth was significantly inhibited, the condition factor was exacerbated, and mortality was significantly increased. Also, significant alterations were observed in zebrafish guts after chronic exposure, which are the opportunistic pathogens Flavobacterium, Aeromonas, and Escherichia. The chronic effects of increased probiotic Cetobacterium, Bacteroides, and Planctomyces deserve further attention. Metagenomic sequencing also showed that genes of core metabolism pathways were affected by TWTP effluent exposure. The study has, for the first time, demonstrated gut microbiota's susceptibility and host health of adult zebrafish to TWTP effluents using aquatic microcosm systems, which are assumed to be clean, thus warranting additional research to reveal their mode of toxicity.