Briefly, bacteria were grown in 150 mL of THB in the presence of 0.05% Tween 80 and 20 mM dl-threonine until the culture reached the early-exponential phase with an OD600 nm of 0.2. The culture was chilled on ice for 30 min, and the bacteria were harvested ABT-737 in vivo by centrifugation and washed extensively with ice-cold sterile distilled water and 10% glycerol in distilled H2O. Cells from the 150 mL culture were suspended in 0.6 mL of 10% glycerol. One hundred

microliters of suspended cells were used for each electroporation, which was conducted in a chilled 2-mm Gap cuvette using a Pulser model of ECM630 (BTX, San Diego, CA) with the following settings: 2.5 kV, 25 μF capacitor and 400 Ω resistor. One milliliter of THB with 0.05% Tween 80 was added to the pulsed cells. After 2-h incubation at 37 °C, the samples were plated on TH agar plates with appropriate selective substance(s). Nine plasmid

p6Srt derivatives were created with a QuikChange site-directed mutagenesis kit (Stratagene, La Jolla, CA): H184A, H204A, F213A, Y236A, L263A, T265A, C266A, R275A and R282A using the primer sets listed in Supporting Information, Table S1. The presence of the desired mutation in each plasmid was confirmed by sequencing the mutagenized plasmids. Actinomyces oris mutants were constructed by transforming check details SrtC1-deficient strain A. orisΔSrtC1 with corresponding p6Srt derivative plasmids based on the allelic-exchange mechanism. Surface proteins were solubilized from A. oris T14V and its mutants using a procedure modified from a mutanolysin digestion method as described previously (Demuth et al., 1996). Briefly, cells from a 10-mL overnight culture were harvested by centrifugation and washed twice with sterile water. The washed cells were suspended in the extraction buffer at a ratio of 4 μL of buffer per milligram of wet cells. The extraction buffer consisted of 26% C1GALT1 melezitose, 10 mM MgCl2, 10 mM phosphate buffer (pH 7.0) and 1000 U mL−1

mutanolysin. After a 5-h incubation at 37 °C, the suspension was centrifuged (10 000 g, 10 min, 4 °C). The supernatant was dialyzed against distilled water using a 10-kDa molecular weight cut off mini Dialysis Units (Pierce, Rockford, IL) and stored at −20 °C for analyses. All chemicals used in the extraction were obtained from Sigma-Aldrich Corp. (St. Louis, MO). Extracted surface proteins were separated on 3–8% Tris-Acetate NuPAGE gels (Invitrogen) and transferred onto nitrocellulose membranes. These membranes were incubated with 1 μg mL−1 monoclonal antibody C8A4 directed against the structural subunit (FimP) of T14V type 1 fimbriae (Cisar et al., 1991). Membranes were washed, incubated with a secondary antibody and developed according to the instructions of WesternBreeze Chromogenic Immunodetection System kit (Invitrogen). Previously, we identified three essential genes (fimQ, fimP and srtC1) for the biosynthesis of type 1 fimbriae in A. oris T14V (Chen et al.