Strain Information

E. coli K-12 MG1655


Genotype: F- lambda- ilvG- rfb-50 rph-1

Serotype: OR:H48:K-

This strain was sequenced by the Blattner laboratory because it approximates wild-type E. coli and "has been maintained as a laboratory strain with minimal genetic manipulation, having only been cured of the temperate bacteriophage lambda and F plasmid by means of ultraviolet light and acridine orange, respectively." (Blattner, et al. 1997). The mutations listed in the genotype are present in most K-12 strains and were probably acquired early in the history of the laboratory strain. A frameshift at the end of rph results in decreased pyrE expression and a mild pyrimidine starvation, such that the strain grows 10 to 15% more slowly in pyrimidine-free medium than in medium containing uracil (Jensen 1993). The ilvG- mutation is a frameshift that knocks out acetohydroxy acid synthase II (Lawther, et al. 1982). The rfb-50 mutation is an IS5 insertion that results in the absence of O-antigen synthesis (Liu and Reeves 1994).

MG1655 was derived and named by Mark Guyer from strain W1485, which was derived in Joshua Lederberg's lab from a stab-culture descendant of the original K-12 isolate. This original E. coli strain K-12 was obtained from a stool sample of a diphtheria patient in Palo Alto, CA in 1922 (Bachmann, B., pp. 2460-2488 in Neidhardt et al.1996, Escherichia coli and Salmonella: Cellular and Molecular Biology, ASM Press).

Media and growth curves

MG1655 grows on LB and M9 minimal medium (+ Glucose + 1ug/ml thiamine). In doing experiments with microarrays, we sought a medium that was both defined and reproducible (unlike LB), yet supported fast growth rates. We now use Neidhardt's MOPS-based rich defined medium (MOPS-RDM). We also sought a commercially available rich defined medium, and finding none tried to grow MG1655 on a medium sold for mammalian cell culture. It grows quite well, but we decided to stick with Neidhardt's medium because it shows a sharper transition to stationary phase.

Recipe for MOPS Rich Defined Medium and MOPS Minimal Medium

Growth curve for MG1655 on MOPS Minimal Medium

Information and growth curve for a commercially available rich defined medium (MEM alpha w/o phenol red)

Growth curves for MG1655 on M9 Minimal Medium


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