The strain Raoultella sp. KDF8 was cultivated on three sources of carbon and energy, glycerol, ethanol and diclofenac, for periods of time ranging from 24 to 72 h. Using thin-layer chromatography, nine classes of phospholipids were detected and the amount of phosphatidylethanolamine (PtdEtn) decreased with increasing cultivation time. Conversely, the ratio of phospholipids having three or four acyls (acyl-phosphatidylglycerol (APtdGro), N-acyl-PtdEtn (NAPtdEtn) and cardiolipin (Ptd2Gro) increased during cultivation. GC-MS analysis showed that the percentage of fatty acids containing a cyclopropane ring increased almost tenfold whereas the amount of fatty acids bearing even-numbered chains dropped to less than one-third after 24 h and 72 h in cultures on glycerol and diclofenac, respectively. Shotgun analysis showed significant changes in the representation of molecular species of phospholipids. For instance, there was a 36-fold change in the ratio of 16:1/16:1/16:1-APtdGro to c17:0/c17:0/c17:0-APtdGro and a 12-fold ratio change for 16:1/16:1/16:1-NAPtdEtn to c17:0/c17:0/c17:0-NAPtdEtn; the Ptd2Gro ratio of 16:1 to c17:0 acids equalled 1750. Our results show that the bacteria overcome destabilization of the inner cytoplasmic cell membrane and a bacterial outer membrane by altering the geometric arrangement of acyl chains, i.e. switching from monounsaturated to cyclopropane fatty acids (16:1 versus c17:0).

Institute of Microbiology Czech Academy of Sciences Vídeňská 1083 142 20 Prague 4 Czech Republic

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