FTT0831c/FTL_0325 contributes to Francisella tularensis cell division, maintenance of cell shape, and structural integrity.
The Francisella FTT0831c/FTL_0325 gene encodes amino acid motifs to suggest it is a lipoprotein and that it may interact with the bacterial cell wall as a member of the OmpA-like protein family. Previous studies have suggested that FTT0831c is surface exposed and required for virulence of Francisella tularensis by subverting the host innate immune response (M. Mahawar et al., J. Biol. Chem. 287:25216-25229, 2012). We also found that FTT0831c is required for murine pathogenesis and intramacrophage growth of Schu S4, but we propose a different model to account for the proinflammatory nature of the resultant mutants. First, inactivation of FTL_0325 from live vaccine strain (LVS) or FTT0831c from Schu S4 resulted in temperature-dependent defects in cell viability and morphology. Loss of FTT0831c was also associated with an unusual defect in lipopolysaccharide O-antigen synthesis, but loss of FTL_0325 was not. Full restoration of these properties was observed in complemented strains expressing FTT0831c in trans, but not in strains lacking the OmpA motif, suggesting that cell wall contact is required. Finally, growth of the LVS FTL_0325 mutant in Mueller-Hinton broth at 37°C resulted in the appearance of membrane blebs at the poles and midpoint, prior to the formation of enlarged round cells that showed evidence of compromised cellular membranes. Taken together, these data are more consistent with the known structural role of OmpA-like proteins in linking the OM to the cell wall and, as such, maintenance of structural integrity preventing altered surface exposure or release of Toll-like receptor 2 agonists during rapid growth of Francisella in vitro and in vivo.
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Gregory T
GT
Robertson
Laboratory of Intracellular Parasites, NIAID, National Institutes of Health Rocky Mountain Laboratories, Hamilton, Montana, USA.
Elizabeth Di Russo
ED
Case
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Nicole
N
Dobbs
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Christine
C
Ingle
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Murat
M
Balaban
Laboratory of Intracellular Parasites, NIAID, National Institutes of Health Rocky Mountain Laboratories, Hamilton, Montana, USA.
Jean
J
Celli
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA Michael.Norgard@UTSouthwestern.edu.
Michael V
MV
Norgard
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D048430:Cell Shape; D005260:Female; D005604:Francisella tularensis / Q000166:cytology* / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D005816:Genetic Complementation Test; D007113:Immunity, Innate; D051379:Mice; D008809:Mice, Inbred C3H; D014406:Tularemia / Q000382:microbiology
D001426:Bacterial Proteins