Subsequent to mutagenesis, cells were plated on M9-glucose Sepantronium price minimal medium including the supplements described above

and mutants click here containing transposon-insertions in the chromosome were resistant to kanamycin. Plates were incubated for 2 days at 37°C under a H2/CO2 (90%/10%) atmosphere (gas-generating kit, Oxoid) and kanamycin-resistant colonies were analysed via a soft-agar overlay technique with benzyl viologen (BV) at a final concentration of 0.5 mM and in a hydrogen atmosphere as described [15]. Colonies with a wild type hydrogenase phenotype developed a dark violet colour while hydrogenase-negative mutants remained creamy white. After purification of putative hydrogenase-negative colonies on LB agar the mutation was transduced into MC4100 using P1kc according to Miller [30] and the phenotype verified. In order to determine the transposon insertion site,

chromosomal DNA was isolated from the mutants [26], digested with KpnI, EcoRI or BamHI and religated. BIIB057 The ligation mixture was PCR amplified using primers KAN-2 FP-1 5′-ACC TAC AAC AAA GCT CTC ATC AAC C-3′ and R6Kan-2 RP-1 5′-CTA CCC TGT GGA ACA CCT ACA-3′ and the PCR product sequenced to determine the precise site of insertion. Preparation of cell extracts and determination of enzyme activity Anaerobic cultures were harvested at an OD600 nm of approximately 0.8. Cells from cultures were harvested by centrifugation at 4,000 × g for 10 min at 4°C, resuspended in 2-3 ml of 50 mM MOPS pH 7.0 buffer and lysed on ice by sonication (30 W power for 5 minutes with 0.5 sec pulses). Unbroken cells and cell debris were removed by centrifugation for 15 min at 10, 000 × g at 4°C and

the supernatant was used as the crude cell extract. Protein concentration of crude extracts was determined [31] with bovine serum albumin as standard. Hydrogenase activity was measured according to [14] except that the buffer used was 50 mM MOPS, pH 7.0. The wavelength used was 578 nm and an EM value of 8,600 M-1 cm-1 was assumed for reduced benzyl viologen. One unit of activity corresponded to the reduction of 1 μmol of hydrogen per min. Formate hydrogenlyase (FHL) Farnesyltransferase activity was measured according to [23] using gas chromatography. Beta-galactosidase assay was performed in microtiter plates according to [32] using a BioRad microplate reader Model 3550 (BioRad, Munich). Polyacrylamide gel electrophoresis and immunoblotting Aliquots of 50 μg of protein from crude cell extracts were separated on 10% (w/v) SDS-polyacrylamide gel electrophoresis (PAGE) [33] and transferred to nitrocellulose membranes as described [34]. Membrane samples were treated with 2× SDS sample buffer [35] containing 10 mM DTT and incubated at room temperature for 60 min prior to loading onto the gel. Antibodies raised against Hyd-1 (1:10000), HycE (1:3000), Hyd-2 (1:20000; a kind gift from F.