Small-cell Segregants from a Possibly Homozygous Diploid Strain of Escherichia Coli.

Ogg, James E. (Colorado State University, Fort Collins) and Ronald D. Humphrey. Small-cell segregants from a possibly homozygous diploid strain of Escherichia coli. J. Bacteriol. 85:801-807. 1963.-Evidence was presented to show that a homozygous possibly diploid strain of Escherichia coli, when grown in a chemically defined medium under the conditions described in this report, will yield small-cell segregants that have haploid characteristics. The segregants have one-half as much deoxyribonucleic acid per cell as the diploid, give exponential survival curves when exposed to X rays, and have fermentative characteristics similar to the original haploid parent strain of the homozygous diploid strain. No detectable changes in surface antigens were associated with the segregation phenomenon. The haploidlike segregants can be converted to the diploid radiation-resistant state by growing them in the presence of camphor vapors.