Bacterial composition of P olygenis ( P olygenis ) bohlsi bohlsi ( W agner, 1901) ( S iphonaptera: R hopalopsyllidae) associated with T hrichomys fosteri ( R odentia: E chimyidae) in the B razilian P antanal wetland

Fleas (Insecta: Siphonaptera) are important vectors of zoonotic bacterial pathogens. However, the bacterial communities hosted by fleas remain poorly understood, especially regarding the interactions between nonpathogenic bacteria and pathogens, as well as the factors shaping these bacterial communities. This study aimed to explore the bacterial composition and diversity between female and male Polygenis ( Polygenis ) bohlsi bohlsi fleas collected from free‐living Thrichomys fosteri (Rodentia: Echimyidae) in the Nhecolândia region of central‐western Brazil. Here, bacterial profiling of fleas was performed using a Next‐Generation Sequencing approach targeting the V3–V4 hypervariable region of the 16S rRNA gene to assess community structure. Bacterial diversity in P. (P.) bohlsi bohlsi fleas varied by sex, as indicated by significant differences in alpha diversity, while beta diversity showed a trend toward separation between sexes. Pseudomonadota was the predominant phylum in the flea microbiome. Ten bacterial genera showed differentially abundance between male and female fleas, including Bartonella spp., which was detected exclusively in males, and Wolbachia spp., which was more abundant in females than in males. Phylogenetic analysis positioned Bartonella gltA sequences detected in two fleas within the same clade as Bartonella harrusi . While the Wolbachia wsp and 16S rRNA sequences detected in P. (P.) bohlsi bohlsi grouped within the supergroups S (associated with pseudoscorpions), gatB sequences grouped with V (cat flea‐related). These findings suggest sex‐associated differences in the microbiome of P. (P.) bohlsi bohlsi fleas and highlight the need for further investigation into the potential role of Wolbachia spp. in shaping flea‐associated microbial communities and their interactions with Bartonella spp.