Elucidating Bacterial Interactions in the Vaginal Microbiome Using Microfluidic Droplet Technology

Elucidating Bacterial Interactions in the Vaginal Microbiome Using Microfluidic Droplet Technology

Corine Jackman¹ (corinemj@umich.edu), Xiaoxia (Nina) Lin^1,2 (ninalin@umich.edu)

¹Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109

²Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109

There is increasing evidence suggesting that the bacteria in the human vagina, referred to collectively as the vaginal microbiome (VMB), plays fundamental roles in womenÕs health and susceptibility to diseases. For instance, bacterial vaginosis (BV), the most common vaginal infection in women of reproductive age in the United States, is characterized by disturbances in the VMB where lactic acid bacteria level is reduced dramatically by an overgrowth of various other bacteria. BV is associated with an increased risk of preterm birth, which has accounted for approximately 75 percent of perinatal deaths in the United States¹. Women with BV also have an increased susceptibility for contracting sexually transmitted infections, such as HIV. The question of how the diverse microorganisms in VMB interact with one another and with their host functionally remains largely unanswered. This is due in part to the immense ecological complexity and the challenge in isolating microbes using conventional cultivation methods.

Microfluidic droplet technology has emerged as a new approach for compartmentalizing cells from microbial communities to perform assays, measure growth, and detect interactions in individual nano- or pico-liter droplets. Advantages of this approach include high-throughput experimentation, and reduced space, time, chemical reagent and labor requirement. In this work, we use microfluidic droplet co-cultivation to investigate pairwise interaction between two vaginal bacteria, specifically Gardnerella vaginalis and a Lactobacillus species. G. vaginalis is associated with BV and Lactobacillus species are believed to promote health by producing lactic acid and reducing pH in the vagina. A previous study demonstrated a severe killing effect on G. vaginalis after incubation in supernatant of Lactobacilli. We investigate this interaction by co-cultivating these species in micro-droplets and comparing growth in the bi-culture verses monocultures. Droplets after incubation under appropriate condition are analyzed through Fluorescent In Situ Hybridization (FISH) using specific probes that hybridize to the 16s rRNA of targeted species. More cell growth in droplets with monocultures in comparison to droplets with bi-cultures indicate a negative interaction. This work demonstrates the effectiveness of using droplet co-cultivation for investigating microbial interactions in the VMB.

Reference:

1. McCormick, Marie C. "The contribution of low birth weight to infant mortality and childhood morbidity." New England journal of medicine 312.2 (1985): 82-90.