For the deletion constructs of pilC and pilQ strain FSC237 was used as template and for the pilT deletion the strain FSC155 buy R406 was used as a template. The sequence for the pilT construct is almost identical between FSC155 and FSC237 except for three substitutions upstream of the deletion in non-coding sequences, and eight substitutions in a downstream pseudogene. The PCR fragments were cloned into the suicide vector pDM4 and the resulting plasmids

pAL12 (pilC), pAL16 (pilQ), and pAL18 (pilT) (Table 2) were introduced into strain FSC237 by conjugal mating as previously described [7]. The in vitro growth rate of the different mutant strains were compared with the wild type strain by measuring OD at different time points, 0 h, 6 h and ON after dilution in Chamberlain medium. RNA isolation find more and RT-PCR Bacteria were grown for 18 h on plates, harvested and suspended in TRIzol reagent (Life Technologies). Total RNA was extracted and treated with

RNase-free DNase I (Roche), phenol extracted, and precipitated by ethanol. An aliquot of the RNA (3 μg) was used to synthesize cDNA using random hexamers (final concentration 25 ng/μl) and Superscript III reverse transcriptase as described by the manufacturer (Life Technologies). In control experiments samples processed without addition of RT enzyme were used. Animal infections F. tularensis strains were grown for 16 h on BCGA before the bacteria were suspended in phosphate buffered saline (PBS) pH 7.4 to an OD540 = 1, which normally corresponds to approximately 2 × 109 bacteria/ml. The bacterial suspension was then diluted in PBS into two doses used for challenge, around 10 and 100 bacteria in a total volume of 100 μl. All bacterial infections were initiated by subcutaneous injections of 6-8 week old C57Black/6 female mice. The study was approved by the Local Ethical Committee on Laboratory Animals in Umeå, Sweden. For competitive index (CI) infections, the mice were infected with a 50:50 mixture of mutant and wild-type strains with around 50 bacteria of each strain. Mice were culled five days post-infection, and the spleens were homogenized in 1 ml of PBS and spread on BCGA.

Individual colonies were analysed by PCR with primers specific for each mutation in order to examine the distribution of each strain. Spleens from at least three animals were click here collected for each pair of strains, Bacterial neuraminidase and at least 200 colonies were analysed by PCR. The CI was calculated for each strain by dividing the ratio of mutant/wt after infection (determined with PCR) with the ratio of mutant/wt before infection (determined by viable count). Statistical analysis was performed with a GraphPad Prism computer software program using a paired Student’s t-test (one-tailed) where P < 0.05 was regarded as significant. Gel electrophoresis and Western blotting Samples were boiled in the presence of SDS and Β-mercaptoethanol for 5 min and then separated on a 12% acrylamide gel by electrophoresis as described by Laemmli [31].