A strain of E. coli lacking the major porin OmpC

Escherichia coli ATCC 8739. This strain differs from the K-12 strain in having the IS1-13 insertion element associated with an upstream promotor and the first 114 bp of ompC. This deletion also eliminates micF, which negatively controls expression of ompF. The corresponding outer membrane proteins OmpC and OmpF, are the two major porins of K-12. Escherichia coli C str. ATCC 8739 expresses only OmpF.