Alkaline lysis solution I, II, and III are solutions that extract small quantities of plasmid DNA from E. coli. 

Solution I destroys cell walls and is more effective when used together with lysozyme. 
Solution II breaks down cell membrane and deactivates protein contained in cells, basifying the cell suspension solution and separating one strand chromosomal cell DNA during the process. 
Solution III neutralizes basic cell suspension solution while precipitating single strand chromosomal DNA with large quantities of potassium.
The suspension solution is removed of protein through phenol extraction, after which plasmid DNA is enriched and purified through alcohol precipitation.