Comparative genomics of Sneathia species: insights into pathogenicity and adaptation to the human niche.

Sneathia are urogenital anaerobes linked to bacterial vaginosis, preterm birth, chorioamnionitis, urethritis, and HPV-mediated cervical carcinogenesis. Two species have been identified: Sneathia vaginalis and Sneathia sanguinegens. Yet, due to their fastidious nature, our knowledge of their pathogenicity is limited. Comparative genomic analysis of 12 Sneathia genomes, including two newly sequenced via whole-genome sequencing, was used to evaluate the pathogenic potential of S. vaginalis and S. sanguinegens. Sneathia species have small genomes (1.25-1.35 Mbp) with low (26.7-29.0%) GC content. The genomes of both species harbor a similar number of subsystems, mostly related to protein processing, metabolism, and energy. Both species encode subsystems for glycogen utilization and lactic and mixed acid fermentation. The genomes of S. vaginalis exhibit a higher potential for carbohydrate and carbohydrate derivative metabolism (gluconate and ascorbic acid catabolism, the Entner-Doudoroff pathway) providing a competitive advantage in nutrient-limited environments. S. sanguinegens genomes show a higher potential for amino sugar (hyaluronic acid and N-acetylneuraminic acid catabolism) and sulfur-containing amino acid metabolism. Sneathia species also encode unique subsystems related to stress response, including oxidative stress, heat shock, and antibiotic resistance. Finally, Sneathia genomes encode both core (shared by all strains) and accessory (specific for species or strains) virulence factors, including exotoxin, additional hemolysins, O-sialoglycoprotein endopeptidase, and adhesins. Both S. vaginalis and S. sanguinegens are highly adapted to the urogenital niche and exhibit high pathogenic capacities. Genomic information revealed potential mechanisms by which these pathogens enhance their competitiveness within the urogenital tract and likely facilitate microbe-microbe cooperation in polymicrobial communities.