biostudies-literatureSaleh DODeutscher Akademischer AustauschdienstEuropean Research CouncilVolkswagen FoundationMinistry of Scientific Research, Egypte1011451https://www.ebi.ac.uk/biostudies/studies/S-EPMC10298799biostudies-literatureUnknown19(6)Both the bacterial flagellum and the evolutionary related injectisome encoded on the Salmonella pathogenicity island 1 (SPI-1) play crucial roles during the infection cycle of Salmonella species. The interplay of both is highlighted by the complex cross-regulation that includes transcriptional control of the flagellar master regulatory operon flhDC by HilD, the master regulator of SPI-1 gene expression. Contrary to the HilD-dependent activation of flagellar gene expression, we report here that activation of HilD resulted in a dramatic loss of motility, which was dependent on the presence of SPI-1. Single cell analyses revealed that HilD-activation triggers a SPI-1-dependent induction of the stringent response and a substantial decrease in proton motive force (PMF), while flagellation remaiPLoS pathogensSPI-1 virulence gene expression modulates motility of Salmonella Typhimurium in a proton motive force- and adhesins-dependent manner.PMC1029879986497191705821Saleh DOErhardt MKlotzsch EWeber WGiralt-Zuniga MDurairaj ACKaganovitch EStrowig THorstmann JAfalseSPI-1 virulence gene expression modulates motility of Salmonella Typhimurium in a proton motive force- and adhesins-dependent manner.Both the bacterial flagellum and the evolutionary related injectisome encoded on the Salmonella pathogenicity island 1 (SPI-1) play crucial roles during the infection cycle of Salmonella species. The interplay of both is highlighted by the complex cross-regulation that includes transcriptional control of the flagellar master regulatory operon flhDC by HilD, the master regulator of SPI-1 gene expression. Contrary to the HilD-dependent activation of flagellar gene expression, we report here that activation of HilD resulted in a dramatic loss of motility, which was dependent on the presence of SPI-1. Single cell analyses revealed that HilD-activation triggers a SPI-1-dependent induction of the stringent response and a substantial decrease in proton motive force (PMF), while flagellation remai2023-01-01T00:00:00Z2023 Jun2025-04-26T04:54:45.55Z2025-04-06T11:14:21.607ZS-EPMC102987993731510610.1371/journal.ppat.1011451