Inoculate L.reuteri into 10 milliliters of MRS broth containing an appropriate antibiotic and incubate overnight aerobically at 37 degrees Celsius. The next day, centrifuge the culture in a pre-chilled centrifuge Discard the supernatant and wash the pellet in two milliliters of standard P1 buffer Centrifuge again and discard the supernatant before resuspending the pellet in 250 microliters of modified P1 buffer. Incubate for one to two hours at 37 degrees Celsius.
Next, add 250 microliters of buffer P2 and mix by inverting four to six times. After five minutes, add 350 microliters of buffer N3 and mix by inverting the tube. Centrifuge at 10, 000 G for 10 minutes and transfer as much supernatant as possible to a spin column.
Centrifuge again for 60 seconds and discard the flow-through. Wash the spin column with 500 microliters of buffer PB and centrifuge, discarding the flow-through. Wash the spin column with 750 microliters of buffer PE and centrifuge at 10, 000 G for 60 seconds.
Discard the flow-through and centrifuge again for 60 seconds to remove any residual buffer. Place the spin column in a 1.5-milliliter microcentrifuge tube. Add 20 to 30 microliters of Dnase-and RNase-free double-distilled water to the spin column filter and leave for one to two minutes before centrifuging at 10, 000 G for 60 seconds.
Perform a standard PCR reaction using plasmid-specific primers with eluate providing the template DNA, including a positive control with a plasmid-derived from the E.coli mini-prep. Running the mini-prep eluate through an agarose gel results in a smear, rather than observable bands. However, subsequent PCR using the eluate as a DNA template produces expected band sizes.
