Environmental Changes Driving Shifts in the Structure and Functional Properties of the Symbiotic Microbiota of Daphnia

Symbiotic microbiota significantly influence the development, physiology, and behavior of their hosts, and therefore, they are widely studied. However, very few studies have investigated the changes in symbiotic microbiota across generations. <i>Daphnia magna</i> originating from the Qinghai-Tibetan Plateau were cultured through seven generations in our laboratory, and the symbiotic microbiota of <i>D. magna</i> were sequenced using a 16S rRNA amplicon to analyze changes in the structure and functional properties of the symbiotic microbiota of <i>D. magna</i> from a harsh environment to an ideal environment. We detected substantial changes in the symbiotic microbiota of <i>D. magna</i> across generations. For example, the genus <i>Nevskia</i>, a member of the gamma-subclass Proteobacteria, had the highest abundance in the first generation (G1), followed by a decrease in abundance in the fourth (G4) and seventh (G7) generations. The gene functions of the microbiota in different generations of <i>D. magna</i> also changed significantly. The fourth generation was mainly rich in fatty acyl-CoA synthase, acetyl-CoA acyltransferase, phosphoglycerol phosphatase, etc. The seventh generation was mainly rich in osmotic enzyme protein and ATP-binding protein of the ABC transport system. This study confirms that the alterations in the structure and functional properties of the symbiotic microbiota of <i>D. magna</i> under changing environments are typical responses of <i>D. magna</i> to environmental changes.