Genomic sequencing reveals regulatory mutations and recombinational events in the widely used MC4100 lineage of Escherichia coli K-12.

The genome of an Escherichia coli MC4100 strain with a lambda placMu50 fusion revealed numerous regulatory differences from MG1655, including one that arose during laboratory storage. The 194 mutational differences between MC4100(MuLac) and other K-12 sequences were mostly allocated to specific lineages, indicating the considerable mutational divergence between K-12 strains.