Lipid composition and the synthesis system that responds to environmental change in Stapylococcus aureus.

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The lipids composition and the synthesis system in Staphylococcus aureus are changeable depending upon environmental stresses. Cardiolipin(CL), a major phospholipids component of the bacteria, has been suggested to play important role in responding to high osmotic pressure. The relative content of cardiolipin increased from 10% ( in 0.85% NaC1 containing medium) to 50%( in 10% NaC1 containing medium), while phsphatidylglycerol(PG) decreased from 65% to 40% of the total phospholipids. Lysylphosphatidylglycerol content remained constant. Cardiolipin synthesis genes(cls) was suspected to play key role in responding to high osmotic pressure. The cls was cloned and expressed in over expression system in S. aureus. It did not produce higher content of CL. The defective strain on S. aureus could not be isolated even after many trials. In E. coli, the defective or destructed cls gene was successfully isolated and it was reported that the strain showed some disorders in cell division process. The cls appears to be essential in S. aueus but further trial should be continued. Among the three sigma factors of S. aureus, sigma B (σ^a B) was suggested to be correlated with the cls expression. The over expression ofσ^B in S. aureus enhanced CL content but the defect of the gene did not affect CL synthesis. The regulatory role of σ^B in CL synthesis needs to further study. Since the destruction of lysylphosphatidylglycerol gene was reported to enhance CL synthesis, the regulatory mechanism of membrane lipid composition and the function should be more globally studied basing on the genome-net work information. In the report, more global insight into bacterial cell membrane was briefly discussed in terms of the molecular structure, function and morphogenesis.