Changes in phospholipid composition of Escherichia coli following γ- and uv-irradiation

Cells of E. coli B/r and B/sub s-1/ in exponential growth and labeled with 14C were analyzed for phospholipid composition after irradition with either γ rays or uv radiation and reincubation for 0 to 180 min. Radiation doses ranged from 1 to 36 krad for B/sub s-1/, and either 3 to 54 krad γ- or 500 to 4000 ergs/mm2 of uv-irradiation for B/r. Phospholipid composition was measured in terms of either 14C activity or phosphorus content. In unirradiated cells it was phosphatidylethanolamine (PE):75-82 percent:phosphatidylglycerol (PG): 14-21 percent; cardiolipin (CL): 2-5 percent. The most significant change with time post-irradiation was an increase in the total amount of CL and CL percent, both of which were strain and dose dependent. In the γ-dose ranges studied, CL percent at 180 min postirradiation increased continuously in B/r (14.2 percent at 54 krad), while it reached a plateau at 9 krad in B/sub s-1/ (9.0 percent). The amounts of CL present showed a four- to fivefold increase over control levels. After 4000 ergs/mm2 uv, the CL percent of B/r only rose to 6 percent and the amount of CL was double that in control cells. After γ doses, up to 9 percent of the recovered lipid activity was present in a nonphospholipid fraction of unidentified composition