Competent Cells

Introduction: The delivery of DNA into the host is required for generation of genetically modified organism. DNA delivery to host is a 3 stage process, DNA sticking to the host cell, internalization and release into the host cell. As a result, it depends on 2 parameters-
Surface chemistry of host cell-Host cell surface charges either will attract or repell DNA as a result of opposite or similar charges. Presence of cell wall (in the case of bacteria, fungus and plant) causes additional physical barrier to the up-take and entry of DNA. 
Charges on DNA-Negative charge on DNA modulates interaction with the host cell especially cell surface.   
Modulation of these two properties is achieved in different methods to deliver DNA into the host cell and it is the topic of the discussion of today’s lecture.

Lab experiment 37.1: Preparation of chemically (CaCl₂) treated E.coli competent cells. 
Background Information: Natural ability of a cell (either bacterium/yeast or mammalian cell) to take up cell free DNA present in extracellular environment is low and only 1% cells are capable to take DNA. Hence, a number of (chemical/physical) treatments make the bacteria competent to take DNA through transformation. A list of agent used for different organism is given in Table 37.1.