This study aims to reveal the role of Lactobacillus in the virulence of Trichomonas vaginalis, the causative agent of the most common non-viral sexually transmitted disease worldwide. The success of this infection is strictly dependent on the ability of this parasite to compete out the vaginal microbial flora. Here, expertises in Trichomonas and Lactobacillus will be combined to understand this unique microbial niche. Trichomonas might critically regulate gene expression to gain control over Lactobacillus population and the participation of these molecules will be revealed by using deep sequencing. Because Lactobacillus is the major component of the healthy vaginal microbiota, the comprehension of this interaction at molecular level will allow us to improve its probiotic activity. Moreover, this study will identify critical antigens that allow this parasite to establish a successful infection in the host which can be used for vaccine therapy.