To generate gene knockouts, Luminespib chemical structure the wild-type cells were electroporated with linearized DNA having a deleted version of the gene using an alkali lysis method

(Gordhan & Parish, 2001). The transformants were then plated on Lemco agar with kanamycin (20 μg mL−1), hygromycin (50 μg mL−1) and X-gal (80 μg mL−1) and incubated at 37 °C for 3–7 days, until blue colonies appeared. These colonies, which were single crossovers (SCOs), were then streaked on Lemco agar with no antibiotics and incubated at 37 °C for 3–7 days, allowing the second crossover to occur. Colonies from nonselective (without antibiotics) agar plates were streaked on Lemco agar plates containing 2% (w/v) sucrose and X-gal (80 μg mL−1) and incubated at 37 °C. The resulting colonies Apoptosis Compound Library molecular weight on the sucrose plates were either spontaneous sucrose-resistant (sucR) mutants (but still SCOs) or double crossovers (DCOs). The rate of spontaneous sucR colonies ranged from 10−4 to 10−5 (Gordhan & Parish, 2001). Spontaneous sucR colonies are blue because they still carry the lacZ gene, whereas any DCOs are white, having lost the lacZ marker gene along with hygromycin and sacB genes. The potential DCOs from the Lemco/sucrose/X-gal

agar plate were streaked on the plates with and without kanamycin to confirm the loss of the marker gene cassette after homologous recombination. Cells (both the wild type and the mutants) were grown with shaking in 100 mL minimal medium held in 250 mL conical flasks and the contents

of 15 flasks were then combined and centrifuged at 10 000 g for 10 min at 4 °C. Cells were washed three times with phosphate-buffered saline (PBS) and once with 0.1 M Tris/HCl buffer (pH 8), centrifuging each time between washes MycoClean Mycoplasma Removal Kit at 10 000 g for 10 min. One milliliter of 0.1 M Tris/HCl buffer (pH 8) was added to the pellet to make a thick paste of cells and the cell suspension was disrupted using a One Shot Cell Disruptor. The cell debris was removed by centrifugation at 10 000 g for 10 min and the cell-free extract was recovered. The concentration of protein was estimated immediately using the biuret method with bovine serum albumin as a standard. One milliliter CFE (8–10 mg protein) of M. smegmatis (wild type and mutants) was incubated at 37 °C for 2 h with 10 μM Mg2+, 1.5 μM NAD+, 250 μM Tris/HCl buffer at pH 8 both with and without 2 μM chorismate (Sigma) as a substrate, in a final volume of 2.3 mL (Marshall & Ratledge, 1971). The reaction was terminated by adding 0.1 mL 5 M HCl and the mixture was extracted twice with ethyl acetate (2 × 5 mL). The ethyl acetate extract was evaporated under vacuum and the residue was dissolved in 5 mL 0.1 M KH2PO4/KOH buffer, pH 7. Salicylic acid was estimated spectrofluorimetrically by its fluorescence at 410 nm following excitation at 305 nm. One milliliter of each CFE prepared from mutants (trpE2, entC and entD), each containing approximately 10 mg protein, was incubated at 37oC for 1 h with 10 μM chorismate, 10 μM Mg2+, 1.