Genomic Analyses Identify Manganese Homeostasis as a Driver of Group B Streptococcal Vaginal Colonization.

Group B Streptococcus (GBS) is associated with severe infections and in newborn populations, including pneumonia, sepsis, and meningitis. GBS vaginal colonization of the pregnant mother is an important prerequisite for transmission to the newborn and the development of neonatal invasive disease; however, our understanding of the factors required for GBS persistence and ascension in the female reproductive tract (FRT) remains limited. Here, we utilized a GBS transposon () mutant library previously developed by our group and identified underrepresented mutations in 535 genes that contribute to survival within the vaginal lumen and colonization of vaginal, cervical, and uterine tissues. From these mutants, we identified 47 genes that were underrepresented in all samples collected, including , a component of the locus, encoding a putative manganese (Mn)-dependent ATP-binding cassette transporter. RNA sequencing analysis of GBS recovered from the vaginal tract also revealed a robust increase of expression during vaginal colonization. We engineered an Δ mutant strain and found by using inductively coupled plasma mass spectrometry that it exhibited decreased concentrations of intracellular Mn, confirming its involvement in Mn acquisition. The Δ mutant was significantly more susceptible to the metal chelator calprotectin and to oxidative stressors, including both HO and paraquat, than wild-type (WT) GBS. We further observed that the Δ mutant strain exhibited a significant fitness defect in comparison to WT GBS by using a murine model of vaginal colonization. Taken together, these data suggest that Mn homeostasis is an important process contributing to GBS survival in the FRT. Morbidity and mortality associated with GBS begin with colonization of the female reproductive tract (FRT). To date, our understanding of the factors required for GBS persistence in this environment remain limited. We identified several necessary systems for initial colonization of the vaginal lumen and penetration into the reproductive tissues via transposon mutagenesis sequencing. We determined that mutations in , the gene encoding a protein putatively involved in manganese (Mn) transport, were significantly underrepresented in all samples collected. We also show that contributes to Mn acquisition and GBS survival during metal limitation by calprotectin, a metal-chelating protein complex. We further demonstrate that a mutant lacking is hypersusceptible to oxidative stress induced by both HO and paraquat and has a severe fitness defect compared to WT GBS in the murine vaginal tract. This work reveals the importance of Mn homeostasis at the host-pathogen interface in the FRT.