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A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
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An intracellularly inducible gene involved in virulence and polyphosphate production in Francisella

Mark I Richards1, Stephen L Michell2, Petra C F Oyston1

  • 1Microbiology, Dstl Porton Down, Salisbury, Wiltshire SP4 0JQ, UK.

Journal of Medical Microbiology
|September 24, 2008
PubMed

Insights

Researchers identified a novel gene, FTN1472/FTT1564, crucial for Francisella tularensis intracellular growth and virulence. This gene encodes a polyphosphate kinase essential for pathogen survival within macrophages and infection in mice.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Pathogen Research

Background:

  • Francisella tularensis is an intracellular bacterium that replicates within macrophages.
  • Identifying genes upregulated during intracellular growth is key to understanding Francisella virulence.
  • Previous studies identified limited high-expression genes in intracellular Francisella.

Purpose of the Study:

  • To discover novel genes upregulated during intracellular growth of Francisella tularensis.
  • To characterize the role of a newly identified gene (FTN1472/FTT1564) in Francisella virulence.

Main Methods:

  • Development of a novel green fluorescent protein (GFP)-based expression plasmid for Francisella.
  • Screening of Francisella tularensis subsp. novicida library for intracellularly expressed genes.
  • Gene sequencing, allelic replacement mutagenesis, polyphosphate analysis, and virulence assays in macrophages and mice.

Main Results:

  • A Francisella screening system identified intracellularly upregulated genes, including known and novel targets.
  • The novel gene FTN1472/FTT1564 was identified and shown to be essential for polyphosphate production.
  • Mutants lacking FTN1472/FTT1564 exhibited impaired intracellular growth and reduced virulence in vivo.

Conclusions:

  • The gene FTN1472/FTT1564 encodes a putative polyphosphate kinase critical for Francisella intracellular survival.
  • This polyphosphate kinase plays a significant role in the virulence of Francisella tularensis.
  • The identified gene represents a potential target for therapeutic intervention against tularemia.

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