This system is mainly designed to extract plasmid DNA from Gram (-) bacteria such as E. coli. Gram (+) bacteria have thicker cell walls so the cell Lysis buffers provided in the kit do not lyse them readily. However, extraction of plasmid DNA from Gram (+) bacteria can still be achieved with additional treatment. After resuspending the pelleted bacterial cells in the PD1 Buffer, add lysozyme to give a final concentration of 3 to 5 mg/ml. Incubate the suspension at 37ºC for 30-60 minutes (or for a shorter time when 5 mg/ml lysozyme is used). This treatment weakens the cell wall of the Gram (+) bacteria. Add PD2, and follow the rest of the protocol. For certain Gram (+) bacteria with thin cell walls, such as Lactobacillus, applying a double amount of PD1, PD2, and PD3 Buffer may be enough to lyse the cells. Yet, we still recommend treating Gram (+) bacteria with lysozyme to facilitate cell Lysis.