Properties of a cell fraction that repairs damage to the cell division mechanism of Escherichia coli.

A factor in bacterial cell extracts which induces cell division in filaments of Escherichia coli produced by irradiation was found to be associated with a heat-labile particulate fraction which sediments at about 100S. Frozen or lyophilized samples of the cell extracts were stable for considerable periods of time. Fractions purified by centrifugation contained 2% of the total protein of the extract but no measurable ribonucleic acid or deoxyribonucleic acid. The extracts were inactivated by incubation with phospholipase A, lipases, and detergents, but not by incubation with selected nucleases and proteases.

Membrane association of conjugally transferred deoxyribonucleic acid in Escherichia coli minicells.

The conjugally acquired deoxyribonucleic acid (DNA) of small, anucleate cells ("minicells") of a mutant strain of Escherichia coli K-12 was found to be predominantly associated with the bacterial membrane. Evidence from X-irradiation studies in vivo shows that there is no decrease in DNA-membrane association under conditions which reduce the DNA to one-sixth its original size and suggests the possibility of multiple DNA-membrane association sites. Preliminary enzymatic studies indicate the involvement of protein, DNA, and lipids in the membrane association of the DNA.