Phenotypic, genomic, and functional characterization of Corynebacterium sp. nov. isolated by droplet-based cultivation from vaginal swabs of a preeclampsia patient.

BACKGROUND

Members of the genus Corynebacterium are widely distributed across human mucosal surfaces and are increasingly recognized as important components of the female reproductive tract microbiota. However, their diversity is underestimated due to limitations of conventional cultivation approaches.

RESULTS

In this study, a novel bacterial strain, designated TJG_1T, was isolated from vaginal swab samples of a pregnant woman with preeclampsia (PE) using droplet-based microfluidic single-cell cultivation. Strain TJG_1T was characterized as a Gram-positive, non-spore-forming, non-motile short rod. Phylogenetic analysis based on the 16 S rRNA gene sequence placed the strain within the genus Corynebacterium, with the highest sequence similarity to Corynebacterium coyleae (97.39%). Whole-genome sequencing revealed a genome size of 2,481,283 bp with a G + C content of 61.52 mol%. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain TJG_1T and its closest relatives were below the accepted species thresholds, supporting its classification as a novel species. Functional genome annotation identified genes associated with metabolism, transport systems, putative antimicrobial resistance, and predicted host interaction-related traits. In vitro assays showed that neither bacterial metabolites nor live cells significantly affected trophoblast cell viability or oxidative stress-related gene expression under the tested conditions. Although alterations in cell migration behavior were observed following exposure to live bacteria, these changes were not accompanied by significant differences in migration-related gene expression.

CONCLUSIONS

Strain TJG_1T represents a novel species within the genus Corynebacterium. This study highlights the utility of droplet-based cultivation for recovering previously underrepresented vaginal bacteria and expands current knowledge of Corynebacterium diversity in the female reproductive tract.