Possible Sec-mediated secretion mechanisms of C. burnetii. Genome analysis predicts a TolC homolog that could mediate type I-like secretion from the periplasm after proteins are transported across the inner membrane by the Sec translocase. C. burnetii also encodes a set of core T4P proteins. T4P are evolutionarily related to type II secretion machinery and have been shown to mediate secretion of several proteins by F. novicida. Sequestration of periplasmic or surface proteins by OMVs is a third option for release of proteins into media supernatants.
Stead et al. BMC Microbiology 2013 13:222 doi:10.1186/1471-2180-13-222