The present invention relates to Escherichia coli variants that have increased antibiotics susceptibility, diffusion efficiency, and transformation efficiency. The variants can minimize the problems caused by biofilm formation such as increased resistance to antibiotics, decreased solute diffusion efficiency, and lowered transformation efficiency. According to the present invention, when selecting genetically-modified E. coli variants, not only a lesser amount of antibiotics is required when selecting desirable variants, but also the reduction of selection efficiency caused by biofilm formation by strains other than the variants to be selected, thus decreasing exhibiting resistance to antibiotics, can be avoided. Additionally, in the process of materials production, the amount of secreted products could be increased due to the increased solute diffusion efficiency. Furthermore, the increased transformation efficiency makes the mass production of useful materials easier.