tularensis strains were richly streaked on MC plates that were incubated in 37°C and 5% CO2 over night. Bacteria were harvested, serially diluted in PBS and 100 μl of a dilution estimated to give approximately 100 colony forming units per plate were evenly spread on MC plates. The plates were incubated at 37°C in an aerobic or microaerobic milieu and the colony size scored after 2, 3, and 6 days of incubation. OxyBlot assay The OxyBlot Protein Oxidation Detection Kit (Chemicon International)

is based on Tigecycline a method for detection of carbonyl groups introduced into proteins by oxidative reactions. The carbonyl groups are derivatized to 2,4-dinitrophenylhydrazone (DNP-hydrazone) by use of 2,4-dinitrophenylhydrazine (DNPH) and can thereafter be detected by immunostaining. The OxyBlot kit was used to compare the amount of oxidized proteins in LVS and ΔmglA grown in an aerobic or a microaerobic milieu. Samples were collected at an OD600 of 0.6-0.7 and the bacteria were lysed using a buffer containing 2 M thiourea, 7 M urea, 4% CHAPS (3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonate), 0.5% ASB-14 (amidosulfobetaine-14), 1.0% DTT, 0.5 × protease inhibitor, and 1% β-mercaptoethanol. The amounts of protein in the samples were determined by use of the Bradford assay (Fermentas, JAK inhibitor St. Leon-Rot, Germany). The assay was carried out according to the manufacturer’s protocol for Standard Bradford assay in microplates.

Equal amounts of proteins were taken from each sample for derivatization and synthesis of negative controls according to the manufacturer’s protocol. Briefly, samples were incubated with 1 × DNPH solution for 15 min at RT to allow derivatization Interleukin-2 receptor of carbonyl-groups to DNP-hydrazone, after which a neutralization solution was added. Negative controls were prepared as the samples with the exception that they were treated with dH2O instead of 1 × DNPH solution, and therefore lack DNP-hydrazone. Negative controls were synthesized in order to ensure the specificity of the antibodies used for detection of DNP-moieties in oxidized proteins. Samples were blotted to PVDF

membranes using a Bio-Dot Microfiltration Apparatus (BioRad), immunostained using a primary Rabbit anti-DNP antibody and a secondary Goat Anti-Rabbit IgG (HRP-conjugated) antibody; and developed with chemiluminescence to visualize the DNP-modifications, as directed by the instructions provided in the OxyBlot Kit. Samples were blotted at a concentration of 2.5 ng of protein in the first well followed by two-fold dilutions thereof. Catalase assay LVS and ΔmglA were cultivated overnight in CDM and thereafter sub-cultured in CDM. When bacteria reached logarithmic growth phase (0.4-0.7 OD600 nm), the OD600 of the cultures were measured and 20-50 μl of culture was withdrawn and transferred to a 96-well UV-clear plate (Greiner Bio-One, Frickenhausen, Germany). To each well, PBS was added to give a final volume of 200 μl.