Abstract:[Background] High salt in diet is currently a major issue in life, and the interaction between intestinal microbes and salt stress has become one of the research hotspots. [Objective] To explore the effect and the underlying mechanism of intestinal microbiota on the salt stress response using D. melanogaster model. [Methods] To evaluate intestinal bacterial load with plate counting and qPCR. To examine the fitness of Drosophila with survival rate and locomotion. To investigate roles of intestinal bacteria in salt stress by generating germ free flies with chemical reagents and antibiotic cocktails. To detect the integrity of the intestinal barrier using dye permeability test. To assess the expression levels of genes utilizing RT-PCR. [Results] High salt induced the dysbiosis of intestinal microbiota in D. melanogaster, leading to a significant increase in intestinal bacterial load. High salt compromised the survival rate and locomotion of D. melanogaster adults. Treated with 0.75 mol/L NaCl, the survival rate of GF female flies was 11% higher than that of counterparts. Additionally, bacterial depletion using antibiotics efficiently improved the survival rate of females challenged with high salt. Intestinal dysbiosis exacerbated high salt-induced intestinal barrier dysfunction with a 8% decrease in Smurf than that in control fly. At the molecular level, the expression levels of Attacin-C and Duox in GF female flies in the case of salt stress were 2.5- and 1.7-fold higher than that of CR flies, respectively. [Conclusion] Intestinal microbiota aggravate the salt stress response in D. melanogaster, resulted in intestinal barrier dysfunction and suppressed innate immune activity in the presence of salt stress.
