Abstract: 【Aim】 Wolbachia is a genus of maternally inherited Gram-negative bacteria, which is one of the most common symbiotic bacteria in insects and can affect host reproduction and behavior in various ways. But the mechanisms of Wolbachia’s influences on hosts are still unclear. This study aims to characterize the effects of the infection of wMelPop, a high toxic Wolbachia strain, on the gut bacteria in male Drosophila melanogaster. 【Methods】 The whole guts of male adults of wMelPop-infected (Pop+) and uninfected (Pop-) D. melanogaster were dissected, from which the total DNA was extracted, respectively. The V3-V4 regions of the 16S rDNA genes of the gut bacteria were sequenced using Illumina NovaSeq platform. The composition, abundance, and α-diversity of the gut bacteria of Pop+ and Pop- were analyzed and compared, and the validity of high-throughput sequencing data of six gut microbial species from three genera with significant differences in expression level was confirmed by qPCR. 【Results】 α-Diversity analysis indicated that wMelPop infection resulted in increased abundance, but decreased diversity of gut bacteria in male D. melanogaster. In the gut of Pop-， the dominant bacterial genera were Acinetobacter, Pseudomonas, Acetobacter and Halomonas. In the gut of Pop+, the relative abundance of Pseudomonas was significantly decreased, while that of Acetobacter and Lactobacillus was significantly increased as compared to those of Pop-. qPCR analysis result revealed that the expression level of the 16S rDNA gene of the total gut bacteria of Pop+ was extremely significantly upregulated as compared to that of Pop-. The expression level of the 16S rDNA gene of A. pomorum in the gut of Pop+ was downregulated to 0.7-fold of that of Pop-, and that of A. tropicalis in the gut of Pop+ was upregulated by about 3 700-fold of that of Pop-. The expression levels of the 16S rDNA genes of L. frutivorans, L. plantarum and L. brevis in the gut of Pop+ were significantly higher than those of Pop-, with that of L. frutivorans showing the highest upregulation level of about 23 000-fold of that of Pop- and that of P. alkaligenes showing downregulation level of about 0.6-fold of that of Pop-. These results were consistent with the trends of the 16S rDNA sequencing results.【Conclusion】The infection of wMelPop significantly affects the relative abundance of gut bacteria in male D. melanogaster, with a significant increase in gut microbiota load of Acetobacter and Lactobacillus. This may be at least one of the mechanisms by which wMelPop infection affects the reproduction and behavior of insect hosts.

Key words: Drosophila melanogaster; wMelPop, males, gut bacteria； Acetobacter, Lactobacillus