Genomic Diversity of Vaginal Lactobacillus crispatus Prophages from South African Women

Abstract

Lactobacillus crispatus is widely associated with optimal sexual and reproductive health outcomes. While L. crispatus genomes commonly harbor prophages, little is known about their genomic diversity and potential inducibility by clinically relevant compounds. We induced and characterized four bacteriophages from four L. crispatus strains isolated from vaginal secretions of South African adolescents. Sequenced viral DNA from induced phages was assembled, and their respective genomes were annotated and compared to bacteriophage reference genomes. All the phage genomes range in size from 42.9 to 48.3 kbp. Of the four phages, UC101 and UC164 shared <90% pairwise intergenomic similarity to reference phages, suggesting that they represent new species. To explore factors potentially associated with prophage activation, L. crispatus strains were exposed to physiological concentrations of copper ions and tenofovir, selected based on their common use by women in Africa and reported associations with altered vaginal bacterial community composition. The presence of phage-like particles following exposure to copper ions (2.0 × 10−6 M–3.0 × 10−6 M) and tenofovir (500 ng/mL) was observed by transmission electron microscopy, suggesting possible prophage activation under these conditions. This study provides new insights into the genomic diversity of inducible L. crispatus phages and presents hypothesis-generating evidence regarding their potential inducibility using copper ions and tenofovir.