Signal transduction pathway mediated by the novel regulator LoiA for

low oxygen tension induced Salmonella Typhimurium invasion

Jiang L, Feng L, Yang B, Zhang W, Wang P, Jiang X, Wang L

PLoS Pathog. (2017) Jun 2;13(6):e1006429

Speaker: Shih-Hsuan Lin (林詩璇)                               Time: 14:00~15:00, Nov. 8, 2017

Commentator: Dr. I-Hsiu Huang (黃一修老師)          Place: Room 601

Abstract:

Salmonella enterica serovars Typhimurium (S. Typhimurium) is a gram-negative, facultative anaerobic rod-shaped bacteria. Salmonella pathogenicity islands (SPIs) are known to encode many genes required for Salmonella pathogenesis. SPI-1, which encoded a type III secretion system ( (T3SS-1) is one of the most important SPIs required for Salmonella invasion. It has been shown that under low oxygen tension, SPI-1 genes expression are activated by HilA, a transcription factor also encoded on SPI-1 ⁽¹⁾. However, additional regulatory mechanisms of SPI-1 in S. Typhimurium are still unclear. A previuos study indicated that deletion of another SPI, SPI-14 in S. Gallinarum and S. Enteritidis showed reducing Salmonella invasion ⁽²⁾. Therefore, SPI-14 might also be involved in Salmonella Typhimurium virulence. In this study, the authors first demonstrated that SPI-14 indeed is required for S. Typhimurium invasion. Their results also showed that a previously uncharacterized transcriptional regulator STM14_1008 (named LoiA), was the virulence determinant in SPI-14 associated S. Typhimurium invasion in mice after oral infection. Additionally, the authors found a ArcB/ArcA two-component system can also regulate gene expression under low O₂ conditions ⁽³⁾. Further analysis using loiA, arcA and arcB mutants showed that binding of LoiA to the promoter of hilD activate hilD expression, leading to the activation of SPI-1 genes, while the positive regulation of ArcA on the loiA gene was indirect. These findings indicated that loiA of SPI-14 can induce S. Typhimurium invasion in low O₂ tension. Results from this study uncovered a novel method in which S. Typhimurium use utilize low-oxygen sensing to initiate invasion and also demonstrated that the multiple SPIs present in the pathogen has cross regulation.

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