Effect of temperature-induced membrane lipid phase transition in recipient cells on conjugation in Escherichia coli K-12

For the unsaturated fatty acid auxotroph (fabB⁻) strain K1059, conditions have been found which allow for maintenance of viability following inhibition of cell growth by.a temperature-induced membrane lipid phase transition. In matings with a F-like, R-factor donor, strain K1059 demonstrated a measurably reduced recipient ability at temperatures below 35.5 C when growth medium was supplemented with elaidate versus oleate. K1059 parent strain, Ymel, did not show variability. in recipient ability when the growth medium was supplemented with either of these two unsaturated fatty acids. Membrane phase transition induced inhibition of recipient cell function is reversible; elaidate-grown cells of strain K1059 held at a temperature of 33.5 C for 30 minutes demonstrating the same mating proficiency as cells remaining at the growth temperature of 39.5 C. Neither pair formation nor maintenance of plasmid once stably inherited appear to be affected by the onset of a membrane lipid phase transition. Furthermore, transfer of ³H-thymidine labeled DNA from donor to recipient cell is only minimally affected by the change in recipient cell membrane lipid phase. Analysis of the results suggest that DNA transferred to recipient cells in possession of ordered phase membrane lipids is either in a fonn which will not permit formation of a stable plasmid or is trapped in a region outside of cytoplasmic membrane.