Low Shear Modeled Microgravity Induces Unexpected Motility Phenotypes in Salmonella Typhimurium

Authors

Yang, J., Barrila, J., Banken, L., Franco Melendez, K. P., Castro, C. L., Kang, B. Y., Gangaraju, S., Davis, R. R., Ott, C. M., McLean, R. J., Nickerson, C. A.

Abstract

Bacteria routinely exhibit unexpected phenotypic and molecular changes in response to spaceflight and spaceflight-analogue conditions, yet the mechanisms by which they sense and respond to these low fluid shear environments are not fully elucidated. We previously demonstrated that spaceflight and low shear modeled microgravity (LSMMG) altered motility and chemotaxis gene expression in Salmonella enterica serovar Typhimurium (S. Typhimurium), raising the possibility that flagella mediate responses of the pathogen to these environments. Herein, we investigated whether LSMMG culture alters S. Typhimurium motility and examined the role of flagella in regulating pathogenesis-associated stress and infection phenotypes. LSMMG enhanced the swimming motility of wild-type S. Typhimurium relative to 1xg controls; a trend which persisted even in the absence of the global stress response regulators Hfq and RpoS. This finding was unexpected, as {Delta}hfq mutants are typically defective for motility under conventional culture conditions. Motility was also observed in the flagella-deficient {Delta}flhDC mutant following LSMMG and 1xg culture, although the relative motility pattern differed relative to wild-type. Collectively, these results indicate that flagella contribute to LSMMG-enhanced motility, but are not strictly required under these conditions. Conditioned supernatant exchange demonstrated that LSMMG-induced motility changes are cell-intrinsic rather than mediated by extracellular factors. While flagella were dispensable for many pathogenesis-related phenotypes tested, their deletion selectively altered the magnitude of LSMMG-associated thermal stress and intracellular survival in human intestinal epithelial cells. Together, these findings demonstrate that motility and pathogenesis-related responses in S. Typhimurium are governed by multiple regulatory pathways that differentially respond to LSMMG and 1xg conditions.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 20 Jun 2026.

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