Gardnerella vaginalis is the only species in the genus Gardnerella. This bacterium is classified as gram-variable because its small coccobacilli yield inconsistent Gram stain results. Based on its genome, G. vaginalis belongs to the high G+C gram-positive group. While it can be a normal part of the vaginal microbiota, its overgrowth causes bacterial vaginosis, which typically presents with mild or undetectable symptoms but can cause pregnancy complications.