B subtilis is naturaly competent you should just grow in specific media and add your DNA in  to growing culture;

Thanks Peter for your answer. Which media do you suggest? I used BHI last time, but it did not work!!

1. Streak B. subtilis  recipient strain on one-half of a TBAB agar plate. Incubate for

18 h at 37°C.

2. Inoculate into  1-3 ml of MB in a 15 ml  test tube, heavily enough so that slight

turbidity is visible. Incubate with aeration for 2 h.

3. Distribute 1 ml of the competent culture into  labelled tubes. Add 0.1 ml or

less of  DNA  to each tube and incubate for 1 h at 37° C with aeration.

4. Add 2.5 ml of SC to each tube. Centrifuge (5OOOg, 10 min, RT) and discard

supernatant.

5. Resuspend  cell pellet in 0.2 ml of SC. Plate 0.1 ml of undiluted suspension

on selective plates.

MB medium contains, per litre:

Bacto-tryptone 10 g

Bacto-yeast extract 5 g

NaCl 10 g

MgCl2 * 6H2O 1 g

SC medium

0.15 M NaCl, 0.01 M sodium citrate, pH 7.0.