In C. burnetii, little is known about the T4BSS regions and the role they play in click here establishing and/or maintaining infection. Coxiella burnetii T4BSS RI contains genes arranged in three linkage groups: (1) icmWCBU1651icmX, (2) icmVdotACBU1647, and (3) icmTicmSdotDdotCdotBCBU1646. 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. Coxiella burnetii is an intracellular pathogen that exhibits a biphasic life cycle that starts with the environmentally stable small-cell variant (SCV) form and converts into the metabolically active and replicative large-cell variant (LCV) form during the first 24 h post infection (hpi) (McCaul & Williams, 1981; McCaul, 1991; Heinzen et al., 1999). Upon infection of a host cell, C. burnetii is trafficked along the endocytic pathway and eventually resides within a parasitophorous vacuole Ivacaftor concentration (PV) retaining the features of a mature
phagolysosome (Akporiaye et al., 1983; Heinzen et al., 1996; Ghigo et al., 2002; Gutierrez et al., 2005; Sauer et al., 2005; Howe & Heinzen, 2006). The early trafficking, enlargement, and maintenance of the C. burnetii PV is dependent Thiamine-diphosphate kinase on C. burnetii protein synthesis (Howe et al., 2003a, b). Infected cells treated with chloramphenicol early during infection contained small tightly bound LAMP-1-positive PVs containing single C. burnetii dispersed throughout the host cell (Howe et al., 2003a, b). However, with the removal of the chloramphenicol, vacuolar fusion resumed, resulting in spacious PVs (SPVs) containing multiple C. burnetii (Howe et al., 2003a, b). Coxiella burnetii-infected cells treated with carbenicillin or nalidixic acid were found to have mature SPVs containing multiple nonreplicating C. burnetii, suggesting that vacuolar development requires metabolically active C. burnetii and is not dependent on bacterial density for complete PV maturation (Howe et al., 2003a, b). These studies demonstrate that the expression of C. burnetii genes during the first 24 hpi of PV niche establishment is crucial for the development of a productive infection.(Coleman et al., 2004). Interestingly, during PV establishment, C.