Larger studies in women at risk for preterm birth are needed to determine whether changes in the vaginal microbiome and/or E. coli inhibitory Tetrahydroberberine activity will provide a biomarker of risk for adverse outcomes including E. coli colonization and associated Loganin sequelae. The potential utility of E. coli inhibitory activity as a biomarker of mucosal health, however, may differ in populations where lactobacilli species are not the dominant microflora. This notion is supported by two small sub-studies of African women who were at high-risk for HIV acquisition. Moreover, in the HIV seroconverters, E. coli inhibitory activity correlated with the concentrations of several pro-inflammatory cytokines and chemokines, suggesting that the activity may be a biomarker of inflammation in high-risk women. In contrast, in the current study, there were no significant correlations between concentrations of mucosal immune mediators and the bacterial groups further indicating that perhaps host immune factors contribute li le to this antimicrobial activity in populations where the microbiome is typically dominated by protective Lactobacillus species. The current study highlights the possibility that E. coli inhibitory activity may be a functional feature of a Lactobacillus crispatus dominant healthy vaginal microbiome. In addition to studies with larger more diverse cohorts, future studies should also include proteomic and metabolomic analyses on the sample to further define the nature and origin of the molecules that contribute to the E. coli inhibitory activity. A longitudinal study in pregnancy is ongoing and will help to elucidate whether high inhibitory activity against E. coli translates to a reduction in sub-clinical or overt genital tract infection and preterm birth. These findings could promote the identification of novel strategies to enhance the antimicrobial activity of genital tract secretions. Further studies are needed to determine if introducing lactobacilli derived molecules or sustaining a L. crispatus dominant microbiome may promote a healthy vaginal environment. These approaches could lead to reduced risk of bacterial vaginosis, chorioamnionitis, preterm birth and perinatal infection and be used as a safer alternative to traditional antibiotics. The use of P. pastoris as a host offers many advantages compared with other expression systems. For example, the yeast can be used to express large amounts of extracellular proteins at relatively li le cost. The preferential secretion of recombinant proteins allows for the direct isolation of target proteins from culture media, eliminating the need for high-cost, low-yield cell disruption. Furthermore, this feature limits the toxicity issues resulting from intracellular accumulation of target proteins. In the P. pastoris expression system, signal peptides are commonly included in commercially available vectors, and so can be a ached to the recombinant protein, causing it to be exported from the cell. Because P. pastoris secretes few intrinsic proteins, the recombinant protein forms the major polypeptide species found in the extracellular growth medium, which facilitates purification of the heterologous protein. However, the P. pastoris system also has several limitations.