A total of seven E. coli strains were used, including the wild-type, genome-reduced and genomic recombinant strains. The analyses were mainly performed on two representative E. coli strains, i.e., the wild-type strain K-12 W3110 and its derivative genome-reduced strain, in which 22% of the genomic sequence was deleted [24]. In addition, five different genome-reduced strains (i.e., the E. coli K-12 MDS42 series, which contained a foreign gene cassette [29]) were used to verify the universal correlation between the size of the colony and the space occupied by the colony.