Coxiella burnetii type IVB secretion system region i genes are expressed early during the infection of host cells

John K. Morgan, Brandon E. Luedtke, Herbert A. Thompson, Edward I. Shaw

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Analysis of the Coxiella burnetii RSA 493 (Nine Mile phase I strain) genome revealed ORFs with significant homology to the type IVB secretion system (T4BSS) of Legionella pneumophila. The T4BSS genes exist primarily at two loci, designated regions I (RI) and II. In C. burnetii, little is known about the T4BSS regions and the role they play in establishing and/or maintaining infection. Coxiella burnetii T4BSS RI contains genes arranged in three linkage groups: (1) icmW→CBU1651→icmX, (2) icmV→dotA→CBU1647, and (3) icmT→icmS→dotD→dotC→dotB→CBU1646. We used reverse transcriptase (RT)-PCR to demonstrate transcriptional linkage within the groups, and that icmX, icmV, and icmT are transcribed de novo by 8 h post infection (hpi). We then examined the transcript levels for icmX, icmW, icmV, dotA, dotB, and icmT during the first 24 h of an infection using quantitative RT-PCR. The expression initially increased for each gene, followed by a decrease at 24 hpi. Subsequently, we analyzed IcmT protein levels during infection and determined that the expression increases significantly from 8 to 24 hpi and then remains relatively constant. These data demonstrate temporal changes in the RNA of several C. burnetii T4SS RI homologs and the IcmT protein. These changes correspond to early stages of the C. burnetii infectious cycle.

Original languageEnglish (US)
Pages (from-to)61-69
Number of pages9
JournalFEMS Microbiology Letters
Issue number1
StatePublished - Oct 2010
Externally publishedYes


  • Coxiella
  • gene expression
  • obligate intracellular
  • type IV secretion system

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology
  • Genetics


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