Isolating Chromosomal DNA from Bacteria

Many methods have been described for isolating
DNA
from prokaryotic cells. The choice of method depends on the degree of purity of the DNA required for the analysis to be performed. Some DNA analyses (e.g., those using restriction enzymes) require DNA of high purity in relatively large amounts. This DNA can be obtained using protocols that include steps to purify DNA once released from cells, as described in this chapter. In contrast, analyses based on polymerase chain reaction (
PCR
) only require very small amounts of DNA whose quality can be crude. Simple, rapid methods allowing DNA to be released from bacterial cells, such as that described in Chapter 7 , are sufficient for most PCR applications. Bacterial DNA can be prepared using extraction kits marketed by several manufacturers. Most of the kits use resins or membranes without organic extraction and/or the alcohol precipitation step to purify DNA. In general, techniques with extraction kits are easily and rapidly performed but are more expensive than their in-house-developed counterparts.