Gut bacterial communities in sand fly vectors from Türkiye.

The gut microbiota of phlebotomine sand flies plays important roles in vector competence and physiology, yet the factors shaping these communities remain poorly understood. We investigated the influence of different vector species on gut bacterial communities of four sand fly species in Türkiye: Phlebotomus tobbi, P. sergenti s.l., P. papatasi, and P. major s.l. Non-blood-fed female sand flies were collected from a single locality in Manisa Province during 2023-2024. Gut samples were dissected under sterile conditions, and bacterial communities were characterized using Illumina sequencing of the V3-V4 region of the 16S rRNA gene. Operational taxonomic units were clustered at 97% similarity using QIIME2, and functional potential was predicted using PICRUSt2. All samples were screened for Leishmania spp. DNA via internal transcribed spacer-1 (ITS-1) real-time PCR. The gut microbiota was dominated by Proteobacteria (81.2%), followed by Actinobacteria, Bacteroidota, and Firmicutes. Species-specific profiles were observed: Wolbachia spp. dominated P. papatasi, Pseudomonas spp. was enriched in P. major s.l., and Bradyrhizobium spp. was abundant in P. sergenti s.l. and P. tobbi. Alpha diversity differed among species (Shannon p = 0.0286; Simpson p = 0.0154), and beta diversity revealed species-specific clustering (PERMANOVA p = 0.001). Despite taxonomic differences, predicted functional analyses indicated largely conserved metabolic profiles. One P. tobbi sample was positive for Leishmania tropica and showed a microbiota dominated by Corynebacterium spp. These findings suggests that species identity shapes gut microbiota in sympatric sand flies, while metabolic profile remains conserved. Additionally, parasite infection may be associated with shifts in microbial composition.