Toxin-antitoxin of Rickettsia determines fatal addiction of the host cells

ABSTRACT: Rickettsia spp. can cause mild to severe human disease. These intracellular bacteria are associated with arthropods, nematodes and trematodes, and usually, are efficiently transmitted transovarially to the progeny of the invertebrate host. We recently demonstrated foreign gene acquisition by lateral gene transfer in Rickettsia genomes. The unexpected presence of laterally transferred toxin-antitoxin (TA) genetic elements (including vapBC) in several Rickettsia genomes has not been connected with the pathogenic process or the host-bacteria relationship. We suspect that vapBC are selfish genetic elements that addict eukaryotic hosts to Rickettsia. We identified a statistical link between the transovarial transmission of Rickettsia in invertebrate hosts and the presence of TA operons, specifically vapBC, in the Rickettsia genome. These TA are neighboring to type IV secretion genes. Tunel assays and whole-genome expression of infected cells showed that antibiotic eradication of TA-containing Rickettsia from the host in cell culture initiates a proapoptotic program. Rickettsia VapC toxins inhibit the growth of transformed Escherichia coli and Saccharomyces cerevisiae. Rickettsia toxin presents in vitro RNase activity. Annexin-V staining and time-lapse video showed that intracytoplasmic injections of VapC toxins in cells cause apoptosis. These data demonstrate that host cells may develop a dependence on Rickettsia spp. expressing the vapBC operon. This would constitute a new evolutionary M-bM-^@M-^\mafia strategyM-bM-^@M-^] of intracellular bacteria based on host addiction. Fresh cells from the human microvascular endothelial cell line (HMEC-1) [26] were infected with R. felis California-2 strain in the presence and absence of antibiotics, at a rate of 5 bacteria per eukaryotic cell. Then, we added or not antibiotics (chloramphenicol 50 M-BM-5g/ml or doxycycline to 40 M-BM-5g/ml) in both experimental (R.felis-infected) and control, mock-infected cells for 6 hours. The cells were harvested and RNA was extracted using the RNeasy Mini Kit (Qiagen). DNA contamination was removed using the Turbo DNA-free Kit (Ambion). RNA were labeled using the Quick Amp Labeling Kit One-color (Agilent) and hybridized onto a Whole Human Genome Microarray, 4x44K (Agilent) as recommended by the manufacturer. Arrays were scanned with DNA Microarray Scanner (Agilent), and data were extracted using Feature Extractor (Agilent).

ORGANISM(S): Homo sapiens

SUBMITTER: Gilles Audoly 

PROVIDER: E-GEOD-22072 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress