Phage DNA
Preparation of bacteriophage DNA
The key difference between phage DNA purification and the preparation of either total cell DNA or plasmid DNA is that for phages the starting material is not normally a cell extract. This is because bacteriophage particles can be obtained in large numbers from the extracellular medium of an infected bacterial culture. When such a culture is centrifuged, the bacteria are pelleted, leaving the phage particles in suspension. The phage particles are then collected from the suspension and their DNA extracted by a single deproteinization step to remove the phage capsid.
This overall process is rather more straightforward than the procedure used to prepare total cell or plasmid DNA. Nevertheless, successful purification of significant quantities of phage DNA is subject to several pitfalls. The main difficulty, especially with lv, is growing an infected culture in such a way that the extracellular phage titre (the number of phage particles per ml of culture) is sufficiently high. In practical terms, the maximum titre that can reasonably be expected for 'A is 1010 per ml; yet 1010 A particles will yield only SOOng of DNA. Large culture volumes, in the range of 500-1000ml, are therefore needed if substantial quantities of A DNA are to be obtained.
Source:
Content:
Gene Cloning and DNA Analysis, an introduction(fifth edition), T. A. Brown