LAUSR

SlyA is a well-known transcription factor that plays important roles in the regulation of diverse physiological functions including virulence and stress response in various bacterial species. The biological effects of slyA have species-specific characteristics. In this study, a phenotype assay showed that slyA gene deletion in Aeromonas hydrophila (ahslyA) decreased biofilm formation capability but did not affect bacterial hemolytic activity or acid stress response. The differentially expressed proteins between ΔahslyA and wild-type strains were compared by label-free quantitative proteomics to further understand the effects of AhSlyA on biological functions. Bioinformatics assays showed that ΔahslyA may be involved in the regulation of several intracellular metabolic pathways such as galactose metabolism, arginine biosynthesis, and sulfur metabolism. A further phenotypic assay confirmed that AhSlyA plays an important role in the regulation of sulfur and phosphate metabolism. Moreover, ahslyA also directly or indirectly regulated at least eight outer membrane proteins involved in the maintenance of cell permeability. Overall, the results provide insights into the functions of ahslyA and demonstrate its importance in A. hydrophila. BIOLOGICAL SIGNIFICANCE: In this study, we compared the DEPs between the transcriptional regulator slyA-deleted and the wild-type A. hydrophila strains using a label-free quantitative proteomics method. The bioinformatics analysis showed that slyA may be involved in the regulation of several metabolic pathways. Subsequent phenotype and growth assays confirmed that ΔahslyA affected sulfur and phosphate metabolism, and OM permeability. Finally, a ChIP-PCR assay further confirmed that AhSlyA directly binds to the promoters of several candidate genes, including sulfur metabolism-related genes. These results indicated that slyA plays an important regulatory role in pleiotropic physiological functions of A. hydrophila, and these functions may be different from those identified in previous reports from other bacterial species.