Reagents

• Page's saline: dissolve 120 mg sodium chloride, 4 mg magnesium sulphate (MgSO4 ■ 7H2O), 4mg calcium chloride (CaCl2 ■ 2H2O), 142mg disodium hydrogen phosphate (Na2HPO4) and 136mg potasium dihydrogen phosphate (KH2PO4) in distilled water and make the volume up to 1l.

Autoclave for 15min at 15psi. Store at 4°C. Shelf life is 6 months.

• Non-nutrient agar: Dissolve 1.5g agar in 100ml Page's saline with gentle heat. Stir or swirl to dissolve. Dispense 20 ml amounts into screw-capped tubes (20 x 150 mm). Autoclave for 15min at 15psi. Store at 4°C. The shelf life is 12 months. For use, the contents of a tube are melted in a boiling water bath and poured into a 9cm sterile Petri dish. After setting, the prepared plates are stored at 4°C. Plates sealed with Parafilm may be stored up to 1 month.

Esherichia coli K12 stock culture; subcultured onto blood agar plate and incubated for 1 day at 37°C. Subculture stored at 4°C for 1 month and then re-cultured.

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