Intracellular biology and virulence determinants of Francisella tularensis revealed by transcriptional profiling inside macrophages.
Summary The highly infectious bacterium Francisella tularensis is a facultative intracellular pathogen, whose virulence requires proliferation inside host cells, including macrophages. Here we have performed a global transcriptional profiling of the highly virulent F. tularensis ssp. tularensis Schu S4 strain during its intracellular cycle within primary murine macrophages, to characterize its intracellular biology and identify pathogenic determinants based on their intracellular expression profiles. Phagocytosed bacteria rapidly responded to their intracellular environment and subsequently altered their transcriptional profile. Differential gene expression profiles were revealed that correlated with specific intracellular locale of the bacteria. Upregulation of general and oxidative stress response genes was a hallmark of the early phagosomal and late endosomal stages, while induction of transport and metabolic genes characterized the cytosolic replication stage. Expression of the Francisella Pathogenicity Island (FPI) genes, which are required for intracellular proliferation, increased during the intracellular cycle. Similarly, 27 chromosomal loci encoding putative hypothetical, secreted, outer membrane proteins or transcriptional regulators were identified as upregulated. Among these, deletion of FTT0383, FTT0369c or FTT1676 abolished the ability of Schu S4 to survive or proliferate intracellularly and cause lethality in mice, therefore identifying novel determinants of Francisella virulence from their intracellular expression profile.
Wehrly
Tara D
TD
Tularemia Pathogenesis Section, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA.
Chong
Audrey
A
Virtaneva
Kimmo
K
Sturdevant
Dan E
DE
Child
Robert
R
Edwards
Jessica A
JA
Brouwer
Dedeke
D
Nair
Vinod
V
Fischer
Elizabeth R
ER
Wicke
Luke
L
Curda
Alissa J
AJ
Kupko
John J
JJ
Martens
Craig
C
Crane
Deborah D
DD
Bosio
Catharine M
CM
Porcella
Stephen F
SF
Celli
Jean
J
D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D003600:Cytosol / Q000382:microbiology; D011992:Endosomes / Q000382:microbiology; D005604:Francisella tularensis / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology*; D020869:Gene Expression Profiling; D005798:Genes, Bacterial; D044404:Genomic Islands; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D010588:Phagosomes / Q000382:microbiology; D013312:Stress, Physiological; D014774:Virulence; D037521:Virulence Factors / Q000096:biosynthesis*
D037521:Virulence Factors