Transformation of calcium-competent cells was carried out by the procedure detailed below: •The competent bacterial cells were thawed briefly and 200 μL of cells was mixed rapidly with plasmid DNA (10-50 ng) in fresh, sterile microcentrifuge tubes and maintained on ice for 30 min. A negative control with competent cells only (no added DNA) was also included. •Cell membranes were disrupted by subjecting cells to heat-pulse (42 °C) for 90 sec. •After heat shock, cells were incubated on ice for 5 min. •Cells were then mixed with 1 mL LB medium and incubated with shaking at 37 °C for 1 h. •For blue/white screening 40 μL of X-gal solution (20 mg mL-1 in dimethylformamide) and 4 μL of the IPTG (200 mg mL-1) was spread on LB-ampicillin (LB-amp) plates with a sterile glass rod. The plate was allowed to dry for 1h at 37 °C prior to spreading of bacterial cells. •Bacterial cells (100-200 μL) were spread and the plate was incubated at 37 °C for overnight. •White colonies were picked from the plates and suspended into LB-amp broth and cultivated to OD600=0.5

In order to minimize self ligation of vector during cloning experiments, the digested DNA was subsequently treated with calf intestinal phosphatase (CIP) [NEB, UK]. The reaction conditions and amount of CIP were optimized and varied from (0.06-1) unit/picomole DNA termini. The dephosphorylation reaction was carried out in 50 μL reaction as follows. Reaction mixture containing no restriction enzyme was treated as control. Reaction was incubated for 1 h at 37 °C and stopped by heat inactivation at 65 °C for 20 min. 2.5.5. Composition of restriction mixture (50 μL) Linearized Plasmid DNA X μL (1 μg) CIP 1 μL (0.06-1 U μL-1) Reaction buffer (10X) 5.0 μL Distilled water Y μL Total volume 50 μL Linearized and dephosphorylated plasmids from each reaction were purified from low melting agarose gel using gel extraction method according to the manufacturer’s protocol (Qiagen gel extraction kit, Germany). 100 ng DNA from each reaction was then ligated in15 μL reaction volume containing 1.5 μL of 10X ligation buffer (NEB, England) and 0.2 μL of T4 DNA ligase to check the efficiency of self ligation after dephosphoryaltion. The ligation mixture was incubated at 16 °C for overnight and transformed into E. coli DH5αcompetent cells.

The isolated DNA was diluted (1:100) with MQ. The concentration (mg mL-1) of the DNA [N] was determined spectrophotometrically by recording absorbance at 260 nm (A260) as: A260 = ε 260[N]where ε 260 is the extinction coefficient of DNA (50 for ds DNA) [N] = concentration (mg mL-1) of DNA The concentration of ds DNA [N] was calculated as [DNA] (mg mL-1) = A260/ε 260 [DNA] (μg mL-1) = A260 × 50 × dilution factor Purity of DNA was checked by measuring absorbance at 260 and 280 nm and calculating the A260/A280 ratio (Sambrook et al., 1989). A DNA sample was considered pure when A260/A280 ranged between 1.8-1.9. An A260/A280 < 1.7 indicated contamination of the DNA preparation with protein or aromatic substances such as phenol, while an A260/A230 < 2.0 indicated possible contamination of high molecular weight polyphenolic compounds like humic substances.

Determination of DNA quantity and purity

as well as commercial methods (MN kit, Germany; Mo-Bio kit, CA, USA; Zymo soil DNA kit, CA, USA) according to the manufacturer’s protocols and compared in terms of DNA yield and purity.

The soil DNA from Pantnagar and Lonar soil samples were also extracted by various manual (Desai and Madamwar, 2007; Agarwal et al., 2001; Yamamoto et al., 1998

Alternatively metagenomic DNA was extracted from the alkaline soil samples by using different commercial kits (UltraClean™, PowerSoil™ [Mo Bio Laboratories Inc., Carlsbad, CA, USA], Nucleospin kit [Macherey-Nagal, Germany] and Zymo soil DNA isolation kit [CA, USA]). The DNA was finally suspended in 100 μL of sterile Milli Q water for further analysis.

Commercial kits

Comparison of yield and purity of crude DNA

Soil (1 gm) was suspended with 0.4 gm (w/w) polyactivated charcoal (Datta and Madamwar, 2006) and 20 μL proteinase K (10 mg mL-1) in 2 mL of modified extraction buffer [N,N,N,N cetyltrimethylammonium bromide (CTAB) 1% w/v, polyvinylpolypyrrolidone (PVPP) 2% w/v, 1.5 M NaCl, 100mM EDTA, 0.1 M TE buffer (pH 8.0), 0.1M sodium phosphate buffer (pH 8.0) and 100 μL RNaseA] [Zhou et al., 1996] in 20 mL centrifuge tubes to homogenize the sample and incubated at 37 °C for 15 min in an incubator shaker at 200 rpm. Subsequently, 200 μL of 10% SDS was added to the homogenate and kept at 60 °C for 2 h with intermittent shaking. DNA was precipitated by adding 0.5 V PEG 8000 (30 % in 1.6 M NaCl) and left at room temperature for an hour (Yeates et al., 1998). The precipitated DNA was collected by centrifugation at 8000 x g at 4 °C. The supernatant was discarded and pellet was dissolved in 1 mL of TE buffer (pH 8.0) and then100 μL of 5 M potassium acetate (pH 4.5) was added and incubated at 4 °C for 15 min. The supernatant was collected after centrifugation at 8000 x g and treated with equal volumes of phenol: chloroform (1:1) followed by chloroform: isoamylalcohol (24:1) at 8000 x g for 15 min

PROTOCOL FOR OPTIMIZATION OF HUMIC ACID-FREE DNA FROM ALKALINE SOILS

For cryopreservation of P, Jalciparum cultures, mostly ring stage parasites at a high parasitemia were obtained. The parasites were pelleted by centrifugation at 200 g for 5 min with minimum de-acceleration. To the pellet, 1.5 volume of the freezing solution (list I) was added drop-by-drop, while shaking the vial gently; the ad4ition was completed in ~ 1 min. The medium was then transferred into a sterile cryovial, which was stored in ~he liquid nitrogen tank

Cryopreservation of Plasmodiumfalciparum cultures

L-[3,4,5-3H (N)]-Ieucine (143Cilmmol), [35S]-dATPaS, 1251-Na (350mCilml) were obtained from Amersham (England, UK).

Radioisotopes

GTG ) were from FMC Bio Products, USA. SDS, ethidium bromide, calf thymus DNA, cesium chloride, tris base, dithiothreitol, IPTG, X -gal, DAB, ficoll, PVP, chloroquine, coomassie brilliant blue, amido black, bovine serum albumin, were from sigma Chemicals Company ( Sigma ) , USA. DEAE -dextran was from Pharmacia, Sweden. Nick translation kits were from Bethesda Research Laboratories BRL ) , USA, and Amersham International plc, UK. Lipofectin was kindly provided by Syntex, Inc. , USA. J3hCG RIA kit was from ICN Micromedic Systems, Inc., USA. Purified hCG 13,000 I.U./ mg was kindly provided by Dr. Y.Y. Tsang, Population Council, USA. HBsAg detection kit was from Abbott Laboratories, USA. Protein molecular mass standards were from Bio Rad Laboratories, USA. DNA size markers were from BRL. All other chemicals were from Glaxo Laboratories, India, and E. Merck, India.

Acrylamide, bisacrylamide, ammonium persulphate, Bio -gel P-4 and TEMED, were from Bio -Rad Laboratories, USA. Agarose ( SeaKem ) and low gelling agarose ( NuSieve

Chemicals.

The cell lines, HEK 293 (human embryonic kidney cells) and HepG2 (human hepatocellular carcinoma) cells were obtained from ATCC. APOBEC3G-HA-293 cell line was obtained from the National Institutes of Health (Bethesda, Maryland, USA) AIDS Repository and grown according to standard procedures. Ecoli strains DHSa or XL-Blue were used for DNA cloning

ell lines and Bacterial strains

Buffer pH range Stock Solutions Volume of Stock A + Stock BCitrate Phosphate 3–5 A: 0.1M solution of citric acid B: 0.2M solution of Na2HPO4pH 3: 39.8 ml A + 10.2 ml B made up to 100 ml pH 4: 30.7 ml A + 19.3 ml B made up to 100 ml pH 5: 24.3 ml A + 25.7 ml B made up to 100 ml Phosphate 6–8 A: 0.2M solution of NaH2P04 B: 0.2M solution of Na2HPO4 pH 6: 87.7 ml A + 12.3 ml B made up to 200 ml pH 7: 39 ml A + 61 ml B made up to 200 ml pH 8: 5.3 ml A + 94.7 ml B made up to 200 ml Tris - HCI 9 A: 0.1M solution of (HOCH2)3CNH2B: 0.1M HCI solution (16.16 ml of 11.35N HCI /L) pH 9: 70 ml A + 30 ml B made up to 200 ml Glycine - NaOH 10 A: 0.1M glycine B: 0.1M NaOH solution pH 10: 50 ml A + 32 ml B made up to 200 ml Phosphate hydroxide 11 A: 0.05M Na2HP04B: 0.05M sodium hydroxide pH 11: 91 ml A + 9 ml B Hydroxide Chloride 12 A: 0.05M KCI solution B: 0.05M KOH solution pH 12: 82 ml A + 18 ml B

Composition of buffers

Table 2.3: Oligonucleotide primers

Primers