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Abstract We previously showed that the physiological concentration of 17β-estradiol in the vaginal environment is sufficient to affect the membrane dynamics and adhesion phenotype of the Lactobacillus crispatus strain CIP104459. However, L. crispatus is a heterogeneous species. Here, we investigated the effect of 17β-estradiol on the recently isolated L. crispatus vaginal strain V4, related to a cluster distant from CIP104459 and at the limit of being a different subspecies. Grown in the same medium, the two strains expressed a highly similar pool of proteins. However, in contrast to CIP104459, L. crispatus V4 showed high aggregation potential and 17β-estradiol promoted this phenotype. This effect was associated with large changes in cell-surface polarity and Lewis acid/base properties. In addition, we observed no effect on the membrane dynamics, contrary to CIP104459. These results can be explained by differences in the properties and organization of the S layer between the two strains. However, as for CIP104459, 17β-estradiol increased biosurfactant production of L. crispatus V4 and their adhesion to vaginal cells. This suggests that 17β-estradiol agonists would be valuable tools to favor a stable re-implantation of L. crispatus in the vaginal mucosa.

Abstract Lactobacilli and estrogens play essential roles in vaginal homeostasis. We investigated the potential direct effect of 17β-estradiol on a vaginal strain of Lactobacillus crispatus, the major bacterial species of the vaginal microbiota. 17β-estradiol (10–6 to 10–10 M) had no effect on L. crispatus growth, but markedly affected the membrane dynamics of this bacterium. This effect appeared consistent with a signal transduction process. The surface polarity and aggregation potential of the bacterium were unaffected by exposure to 17β-estradiol, but its mean size was significantly reduced. 17β-estradiol also promoted biosurfactant production by L. crispatus and adhesion to vaginal VK2/E6E7 cells, but had little effect on bacterial biofilm formation activity. Bioinformatic analysis of L. crispatus identified a membrane lipid raft–associated stomatin/prohibitin/flotillin/HflK domain containing protein as a potential 17β-estradiol binding site. Overall, our results reveal direct effects of 17β-estradiol on L. crispatus. These effects are of potential importance in the physiology of the vaginal environment, through the promotion of lactobacillus adhesion to the mucosa and protection against pathogens.