Intracellular Salmonella Paratyphi A is motile and differs in the expression of flagella-chemotaxis, SPI-1 and carbon utilization pathways in comparison to intracellular S. Typhimurium

PLoS Pathog. 2022 Apr 5;18(4):e1010425. doi: 10.1371/journal.ppat.1010425. eCollection 2022 Apr.

Abstract

Although Salmonella Typhimurium (STM) and Salmonella Paratyphi A (SPA) belong to the same phylogenetic species, share large portions of their genome and express many common virulence factors, they differ vastly in their host specificity, the immune response they elicit, and the clinical manifestations they cause. In this work, we compared their intracellular transcriptomic architecture and cellular phenotypes during human epithelial cell infection. While transcription induction of many metal transport systems, purines, biotin, PhoPQ and SPI-2 regulons was similar in both intracellular SPA and STM, we identified 234 differentially expressed genes that showed distinct expression patterns in intracellular SPA vs. STM. Surprisingly, clear expression differences were found in SPI-1, motility and chemotaxis, and carbon (mainly citrate, galactonate and ethanolamine) utilization pathways, indicating that these pathways are regulated differently during their intracellular phase. Concurring, on the cellular level, we show that while the majority of STM are non-motile and reside within Salmonella-Containing Vacuoles (SCV), a significant proportion of intracellular SPA cells are motile and compartmentalized in the cytosol. Moreover, we found that the elevated expression of SPI-1 and motility genes by intracellular SPA results in increased invasiveness of SPA, following exit from host cells. These findings demonstrate unexpected flagellum-dependent intracellular motility of a typhoidal Salmonella serovar and intriguing differences in intracellular localization between typhoidal and non-typhoidal salmonellae. We propose that these differences facilitate new cycles of host cell infection by SPA and may contribute to the ability of SPA to disseminate beyond the intestinal lamina propria of the human host during enteric fever.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism
  • Carbon / metabolism
  • Chemotaxis*
  • Flagella / genetics
  • Flagella / metabolism
  • Intercellular Signaling Peptides and Proteins
  • Phylogeny
  • Salmonella paratyphi A* / metabolism
  • Salmonella typhimurium

Substances

  • Bacterial Proteins
  • Intercellular Signaling Peptides and Proteins
  • lambda Spi-1
  • Carbon

Grants and funding

This work was supported by the Infect-Era program, SalHostTrop project (“Understanding the Human-Restricted Host Tropism of Typhoidal Salmonella”, 2016-2020) and by the France Génomique National infrastructure, funded as part of “Investissement d’avenir” program managed by Agence Nationale pour la Recherche (ANR-10-INBS-09 contract). The work at the Gal-Mor laboratory was supported by grant numbers: 2616/18 from the joint ISF-Broad Institute program; 3-12435 from Infect-Era /Chief Scientist Ministry of Health; I-41-416.6-2018 from the German-Israeli Foundation for Scientific Research and Development (GIF, awarded to OGM and MH); and A128055 from the Research Cooperation Lower Saxony – Israel (The Volkswagen Foundation, awarded to OGM, MH and GG). The funders had no role in study design, data collection, and interpretation, or the decision to submit the work for publication.