The Xenogeneic Silencer Histone-Like Nucleoid-Structuring Protein Mediates the Temperature and Salinity-Dependent Regulation of the Type III Secretion System 2 in Vibrio parahaemolyticus

• Published in: Journal of bacteriology Vol. 205; no. 1; p. e0026622
• Main Authors: Pratama, Andre, Ishii, Eiji, Kodama, Toshio, Iida, Tetsuya, Matsuda, Shigeaki
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 26-01-2023
• Subjects: Bacteria; Bacterial Proteins - metabolism; Bacteriology; Binding sites; Deoxyribonucleic acid; Diarrhea; DNA; Gene deletion; Gene expression; Gene Expression Regulation, Bacterial; Gene regulation; Histones; Histones - genetics; Histones - metabolism; Humans; Mutation; Pathogenicity; Pathogens; Proteins; Regulatory sequences; Research Article; Salinity; Salinity effects; Seafood; Secretion; Temperature; Temperature dependence; Transcription activation; Type III Secretion Systems - genetics; Type III Secretion Systems - metabolism; Vibrio parahaemolyticus; Vibrio parahaemolyticus - genetics; Virulence; Virulence Factors - genetics; Virulence Factors - metabolism; Vibrio parahaemolyticus; histone-like proteins; virulence regulation; xenogeneic silencing; pathogenicity islands; type III secretion system
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/jb.00266-22

The marine bacterium Vibrio parahaemolyticus is a major seafood-borne pathogen that causes acute diarrhea in humans. A crucial virulence determinant of V. parahaemolyticus is the type III secretion system 2 (T3SS2), which is encoded on the Vibrio parahaemolyticus pathogenicity island (Vp-PAI), in which gene expression is dependent on environmental cues, such as temperature and salinity. This characteristic may implicate the adaptation of V. parahaemolyticus from its natural habitat to the human body environment during infection; however, the underlying mechanism remains unknown. Here, we describe the regulatory role of the histone-like nucleoid-structuring protein (H-NS), which is a xenogeneic silencing protein, in T3SS2 gene expression through the conditional silencing of the gene encoding a master regulator of Vp-PAI, VtrB. The
deletion canceled the temperature- and salinity-dependent differential T3SS2 gene expression. H-NS bound to the
promoter containing AT-rich sequences, and the binding sites partially overlapped the binding sites of two positive regulators of
(i.e., VtrA and ToxR), which may block the transcriptional activation of
. H-NS-family proteins multimerize along the DNA strand, forming stiffened filament and/or bridging DNA duplexes for its target silencing. In V. parahaemolyticus, mutations at conserved residues that are required for the multimerization of H-NS abolished the repressive activity on VtrB expression, supporting the contention that H-NS multimerization is also critical for
silencing in V. parahaemolyticus. Taken together, these findings demonstrate the principal role of H-NS as a thermal and salt switch with sensory and regulatory properties for ensuring T3SS2 gene regulation in V. parahaemolyticus.
In the major seafood-borne pathogen Vibrio parahaemolyticus, the type III secretion system 2 (T3SS2) is a major virulence factor that is responsible for the enterotoxicity of this bacterium. The expression of T3SS2 varies according to changes in temperature and salinity, but the mechanism via which T3SS2 expression is regulated in response to such physical cues remains unknown. Here, we report that H-NS, a xenogeneic silencer that is widespread in Gram-negative bacteria, modulates the entirety of T3SS2 gene expression through the transcriptional silencing of the gene encoding the T3SS2 master regulator VtrB in a temperature- and salinity-dependent manner. Thus, our findings provide insights into how this pathogen achieves the appropriate control of the expression of virulence genes in the transition between aquatic and human environments.