Determination of invasiveness HeLa S3 cell line (ATCC CCL-2.2) between passages 8 and 15 was grown in F12K medium containing 10% HI-FBS at 37°C with 5% CO2. Twenty-four hours prior to infection, the cells were suspended and cultured in 25 cm2 culture flasks (Corning, Corning, NY) at a concentration of 2 × 106 cells/flask and replaced in the incubator. Before infection, cells from 1 flask were detached and counted. For infection with B. melitensis 16 M or its

derivatives, FK506 chemical structure the medium overlying the HeLa monolayers was replaced by a bacterial inoculum grown overnight in F12K cell culture media, at a multiplicity of infection of 1,000 bacteria per cell (MOI 1,000:1). Bacteria were centrifuged onto the cells at 800 × g for

10 min, followed by 30 min of incubation at 37°C with 5% CO2. Then, cells were washed once with phosphate buffer solution (PBS) to remove extracellular bacteria and subsequently re-incubated for 1 h in F12K media supplemented with 100 μg ml-1 of gentamicin solution (Sigma, St. Louis, MO). To determine the viable number of intracellular bacteria, infected cultures were washed 3× with PBS and then lysed with 0.1% Triton X-100 (Sigma). Lysates were serially diluted and cultured on TSA learn more plates for quantification of CFU. Isolation of total RNA from B. melitensis 16 M Total RNA was isolated by phenol-chloroform extraction from 4 different cultures of B. melitensis 16 M grown in F12K supplemented with 10% HI-FBS at late-log and stationary JSH-23 in vitro growth phases, as previously described [66]. Briefly, ice-cold ethanol/phenol solution was added to the B. melitensis culture, and the bacteria were recovered by centrifugation. The media was then removed and the pellet suspended in TE buffer-lysozyme solution containing 10% SDS (Ambion, Austin, TX). After 2 min of incubation, acid water-saturated phenol (Ambion) was added to the lysate and mixed, and the sample was subsequently

incubated for 6 min at 64°C. Tubes were kept on ice for at least 2 min and then centrifuged at maximum speed. The upper layer, containing the RNA, was transferred to a new tube, mixed Ureohydrolase with an equal volume of chloroform (Sigma) and then separated by centrifugation. The aqueous phase was mixed with 100% cold ethanol and stored at -20°C. After at least one hour of incubation, RNA was pelleted by centrifugation, washed in 80% ethanol and suspended in DEPC-treated water (Ambion) containing 2% DTT and 1% RNase inhibitor (Promega, Madison, WI). Contaminant genomic DNA was removed by RNase-free DNase I treatment (Ambion) according to the manufacturer’s instructions, and samples were stored at -80°C until used. RNA concentration was quantified using the NanoDrop® ND-1000 (NanoDrop, Wilmington, DE), and quality was determined using the Agilent 2100 Bioanalyzer (Agilent, Palo Alto, CA). Isolation and labeling of B.