Altered phospholipid metabolism in a temperature-sensitive mutant of a thermophilic bacillus

The phospholipid metabolism of a temperature-sensitive mutant of a thermophilic bacillus was studied after the shift from a permissive (58°C) to a restrictive (65°C) growth temperature. During the short period of growth of the mutant at 65°C, the proportions of cardiolipin and its 3-acyl derivative (lyso-cardiolipin) increased, and the proportions of phosphatidylglycerol and phosphatidylethanolamine decreased on cell dry weight basis. In ³²P incorporation and turnover experiments, phosphatidylglycerol showed the most rapid uptake and loss of the label. Turnover of cardiolipin, limited to a short period, ceased 18 min after the shift, as did the turnover of phosphatidylethanolamine. In the absence of net phospholipid synthesis, there was a quantitative conversion of phosphatidylglycerol to cardiolipin and an increase in the proportion of lyso-cardiolipin. Chloramphenicol, added to the medium at the time of the shift, reduced the rate of phospholipid synthesis, prevented the increase in the proportions of cardiolipin and lyso-cardiolipin, and slowed the decrease in the proportions of the other two phospholipids. The results indicated a defect in the regulatory mechanism(s) of phospholipid metabolism in the mutant at the restrictive temperature.Nonstandard Abbreviations WT parental strain, thermophilic bacillus - TS-13 temperature-sensitive mutant of a thermophilic bacillus - CL cardiolipin - PG phosphatidylglycerol - PE phosphatidylethanolamine - l-CL lyso-cardiolipin