Stringent Response Regulates the Persister Formation and Virulence of Vibrio splendidus

Vibrio splendidus is an important opportunistic pathogen that causes diseases in aquatic animals, and its persisters increase the difficulty of aquaculture disease control. The stringent response is a central pathway in bacteria for coping with environmental stress, and the signaling molecule (p)ppGpp, synthesized under the regulation of RelA/SpoT homologs, is closely associated with persister formation and virulence modulation. However, the regulatory mechanisms linking the stringent response to persister formation and virulence in V. splendidus remain unclear. In this study, the core gene deletion strains ΔrelA and ΔrelAΔspoT were constructed via homologous recombination. Combined with D₂O single-cell Raman spectroscopy, transcriptomics, and phenotypic assays, we systematically characterized the biological effects of stringent response inactivation. The results showed that the loss of relA and spoT significantly reduced persister formation and key virulence traits while enhancing biofilm formation. Single-cell Raman spectroscopy analysis indicated that persisters remained metabolically active, accompanied by changes in different cellular components. Transcriptome analysis revealed that the absence of stringent response affected multiple pathways, including ribosomal function, energy metabolism, two-component systems, and quorum sensing. Additionally, the sigma factor RpoS may potentially exert a compensatory function in ΔrelAΔspoT strain, but this requires further validation. In conclusion, the stringent response positively regulates persister formation and virulence in V. splendidus, despite the existence of complex regulatory mechanisms. This study provides a theoretical basis for the development of anti-infective strategies targeting stringent response in aquatic pathogens.