Chemotaxis and selective interactions of Trichomonas vaginalis with the vaginal bacteria
Trichomonas vaginalis is an extracellular parasite that inhabits the human genital tract, yet little is known about how it senses and responds to the vaginal microbial ecosystem. Here, we show that T. vaginalis exhibits chemotactic behavior on semisolid surfaces, forming multicellular assemblies that coordinate collective migration. Parasite colonies display both attractive and repulsive responses to diffusible signals and show strain-specific mutual avoidance. We further demonstrate that T. vaginalis is strongly attracted to acidic environments, revealing a niche-adapted pH taxis. Since vaginal bacteria shape local pH, we examined parasite responses to representative members of the vaginal microbiota. T. vaginalis preferentially migrated toward Lactobacillus gasseri over Gardnerella vaginalis and showed no attraction to Escherichia coli. This selective migration correlated with a robust response to lactic acid, a major metabolite produced by lactobacilli. In co-culture with equal numbers of L. gasseri and G. vaginalis, the parasite preferentially bound to L. gasseri and exhibited enhanced growth only in its presence. Together, these findings identify pH taxis, bacteria-directed migration, and preferential association with Lactobacillus as previously underappreciated behavioral traits of T. vaginalis.