RNA-seq reveals the critical role of the Glaesserella parasuis hfq gene in stress response and virulence

Hfq protein is widely present in most bacteria and participates in regulating the expression of bacterial virulence factors in various gram-negative bacteria. Mutations in the hfq gene lead to decreased bacterial virulence in Glaesserella parasuis. However, the molecular mechanism between Hfq protein and bacterial virulence remains unknown. In this study, an hfq gene in-frame deletion mutant strain was constructed through the natural transformation method, the differences in bacterial biological characteristics between mutant and parent strains were compared, and the changes in bacterial transcriptome caused by hfq gene mutations were determined through RNA-seq. The results revealed that the hfq gene mutation did not alter the bacterial growth rate or morphology. However, the Δhfq mutant exhibited significantly reduced survival under stress conditions, including 42 °C heat shock, 100 mM H₂O₂, 8 mM HCl, and iron-deficient environments, compared with the parent strain. Moreover, the mutation led to attenuated bacterial virulence in the mouse infection model. RNA-seq results revealed that the different expressed genes are involved in the stress response, iron ion metabolism, and transcriptional regulation, and some potential virulence factors, such as sodA and rpoC in Glaesserella parasuis were downregulated. Overall, these findings provide preliminary insights into the molecular mechanism between Hfq protein, stress response, and bacterial virulence.