Physiology of Escherichia coli K-12 during conjugation: altered recipient cell functions associated with lethal zygosis.

The number of viable F(-) cells decreases when Escherichia coli recipient cells are mixed with an excess of Hfr cells. Evidence is presented showing that lethal zygosis was accompanied by changes in the physiology of the recipient cells, including (i) inhibition of deoxyribonucleic acid synthesis, (ii) inhibition of beta-galactosidase induction, (iii) altered transport and accumulation of galactosides, and (iv) leakage of beta-galactosidase into the supernatant fluid. The results are discussed in terms of possible conjugation-associated changes that, at high Hfr to F(-) ratios, lead to lethal zygosis.