Competent Cells
DH5α, BL21, and TOP10 are strains of Escherichia coli
DH5α:
DH5α is a commonly used strain of E. coli that is widely used for routine cloning and plasmid propagation. It is known for its high transformation efficiency, making it suitable for cloning experiments where a large number of transformants are desired. DH5α is often used in molecular biology labs for plasmid amplification, routine cloning, and propagation of recombinant DNA.
BL21:
BL21 is another strain of E. coli that is frequently used for protein expression. It is specifically engineered to lack the lon and ompT proteases, which can degrade recombinant proteins. BL21 strains are often used in heterologous protein expression systems, where foreign genes are cloned into expression vectors and introduced into BL21 cells for protein production.
TOP10:
TOP10 is a derivative of DH10B strain that has been optimized for high-efficiency transformation and is commonly used for routine cloning and plasmid propagation. It is similar to DH5α in its applications and is often chosen for its convenience and reliability in cloning experiments.
BL21 (DE3) showed the highest level of expression in inclusion bodies followed by Rosetta-gami (DE3) and Shuffle T7.
Competent Cells:
Competent cells refer to bacterial cells that have been treated to make them capable of taking up exogenous DNA efficiently through transformation. There are many other strains of competent cells available besides DH5α, BL21, and TOP10, each with unique characteristics optimized for specific applications. 
