Isolation and characterization of a novel vaginal Corynebacterium strain from a patient with preeclampsia using droplet-based single-cell cultivation

The genus Corynebacterium constitutes an important component of the female reproductive tract microbiota. Increasing evidence suggests that some Corynebacterium species may have opportunistic pathogenic potential rather than acting solely as commensal colonizers. However, the cultivable diversity and potential functional roles of vaginal Corynebacterium species in pregnant women remain poorly understood. In this study, a novel Corynebacterium strain, designated strain TJG_2 T , was isolated from the vaginal secretion of a pregnant woman with preeclampsia (PE) using a droplet-based microfluidic single-cell cultivation platform. Strain TJG_2 T was Gram-stain-positive, non-spore-forming and non-motile, with short rod-shaped cells. Phylogenetic analysis based on the 16S rRNA gene sequence assigned the strain to the genus Corynebacterium . The closest validly named species was Corynebacterium freneyi ISPB 6695110 T , with 97.72% 16S rRNA gene sequence similarity. Whole-genome sequencing revealed a genome size of 2,513,377 bp and a DNA G + C content of 58.98 mol%. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain TJG_2 T and its closest relative were below the accepted species thresholds, supporting its classification as a putative novel species. Homology-based annotation identified genes assigned to carbohydrate metabolism, amino acid metabolism, energy metabolism and membrane transport categories. In vitro assays showed that live bacteria gradually reduced HTR-8/SVneo cell viability after prolonged co-culture. After 24 h of co-culture, live bacterial exposure significantly altered cell migration at the phenotypic level. However, no significant changes were detected in the expression of selected genes related to invasion or migration.