A Microbial Piñata: Bacterial Endosymbionts of Trichomonas vaginalis Come in Different Flavors

Abstract

The protozoan parasite Trichomonas vaginalis causes trichomoniasis, a prevalent human urogenital infection with significant morbidity that is commonly associated with vaginal dysbiosis. Exacerbation of T. vaginalis pathogenicity has been related to endosymbionts, including mycoplasma, and thought for a while to be solely attributable to Mycoplasma hominis. In a recent publication, Margarita and colleagues (https://journals.asm.org/doi/10.1128/mbio.00918-22) showed that endosymbiosis extends to a second species of mycoplasma known as "Candidatus Mycoplasma girerdii." Those authors confirmed the strong association of T. vaginalis with both species of mycoplasma by reassessing clinical samples. Additionally, they showed that in vitro symbiosis of protozoa and bacteria resulted in the modulation of gene expression of T. vaginalis and enhancement of parasite cytoadhesion and hemolytic activity in culture assays. In this commentary, we portray T. vaginalis as a synergistically interacting multimicrobe organism-a "microbial piñata"-whose endosymbionts contribute significantly to the pathophysiology of this medically important protozoan parasite.

Keywords: Trichomonas vaginalis; endosymbiont; mycoplasma; sexually transmitted infections; symbiosis; trichomoniasis; vaginal microbiome.

FIG 1

Trichomonas vaginalis portrayed as a piñata. The standard drug metronidazole, upon intracellular activation, binds to DNA and metabolic proteins, killing the parasite. The burst of protozoan cells releases variants of a specific family of RNA virus or Trichomonasvirus, represented by the geometric capsids in different colors, and two species of Mycoplasma, represented by the blue and yellow oval-shaped bacterial cells with circular DNA. The association of this infection with vaginal dysbiosis, a BV-like species-diversified cervicovaginal microbiome, is represented by bacterial cells of various colors at the bottom of the figure. T. vaginalis endosymbionts contribute to the pathobiology of trichomoniasis, as reviewed by Dessi et al. (7). This has now been expanded to a new species of mycoplasma endosymbiont by Margarita et al. (https://journals.asm.org/doi/10.1128/mbio.00918-22), the study that is the focus of this commentary.