Mad science with the Bean Team
Newly constructed plasmids are integrated into E. coli as a means to screen correctly assembled colonies, replicate it into quantifiable amounts, and then isolate it back out to be used for the next assembly.
While the antibiotic resistance and blue/white coloration suggest a successful goldengate assembly, this can be further verified through a restriction enzyme digest and gel electrophoresis.
It is much cheaper to reproduce your own stocks of electrocompetent cells than to be consistently buying more. Competent cell preparation consists of multiplying a strain of cells in a nutrient rich broth, spinning them down, and rinsing them several times to remove any salts present. These new stocks of cells are then aliquoted into eppendorfs and stored at -80*C.