Bacterial DNA isolation: A loopful of bacterial mass taken from an isolated clone on
LB-agar plate was inoculated into 3 ml of Luria Broth (LB) and allowed to grow for 48 h
at 2871 1C on an orbital shaker (150 rpm). The bacterial cell mass was harvested in
pellet by centrifugation at 10,000 rpm for 1 min. The cell mass was lyzed by
suspending in 10 mM Tris EDTA buffer (TE) containing 20 mg ml−1 lysozyme, followed
by incubation at RT for 10 min. The cellular proteins in the lysate were removed by
three extractions with phenol:chloroform (1:1 v/v) followed by chloroform:isoamyl
alcohol (25:1 v/v). The total DNA in the aqueous phase was precipitated with equal
volume of isopropanol in the presence of 0.25 M sodium acetate, pH 5.2. The bacterial
DNA was collected in pellet by centrifugation at 10,000 rpm, for 5 min. The DNA pellet
was washed once with 70% ethanol and allowed to dry at RT. The Dried DNA pellet was
dissolved in 100 μl of TE buffer and stored at −20 1C until used. The quality of DNA
isolated from bacteria was determined by horizontal agarose 0.7 per cent containing
ethidium bromide @1 mg per ml gel electrophoresis in 1 TAE (Tris Acetate EDTA)
buffer at 75 V for 1 h. The DNA bands were visualized and photographed under a UV
transilluminator in ‘UltraCam Gel documentation system’.