Cyclopropanation of membrane @entity1474 is not essential to the acid stress response of @entity7878 subsp. XXXX .

@entity845 @entity72986 @entity26135 @entity3874 @entity1474 @entity5031 @entity3795 @entity465 @entity7878 @entity1068
@entity72986 (CFAs) are synthetized in situ by the transfer of a @entity845 group from @entity3874 to a double bond of @entity5031 chains of membrane phospholipids. This conversion, catalyzed by the @entity3795 synthase enzyme, occurs in many bacteria and is recognized to play a key role in the adaptation of bacteria in response to a drastic perturbation of the environment. The role of CFAs in the acid tolerance response was investigated in the lactic acid bacterium @entity7878 MG1363. A mutant of the @entity3795 gene was constructed by allelic exchange. The @entity3795 gene encoding the @entity3795 synthase was cloned and introduced into the mutant to obtain the @entity465 for homologous system studies. Data obtained by gas chromatography (GC) and GC-mass spectrometry (GC-MS) validated that the mutant could not produce @entity3795 . The @entity3795 levels in both the wild-type and complemented strains increased upon their entry to stationary phase, especially with acid-adapted cells or, more surprisingly, with @entity1068 -adapted cells. The results obtained by performing quantitative reverse transcription-PCR (qRT-PCR) experiments showed that transcription of the @entity3795 gene was highly induced by acidity (by 10-fold with cells grown at pH 5.0) and by @entity1068 (by 9-fold with cells grown with 6% @entity1068 ) in comparison with that in stationary phase. Cell viability experiments were performed after an acidic shock on the mutant strain, the wild-type strain, and the @entity465 , as a control. The higher viability level of the acid-adapted cells of the three strains after 3 h of shock proved that the cyclopropanation of @entity1474 is not essential for @entity26135 survival under acidic conditions. Moreover, fluorescence anisotropy data showed that @entity3795 itself could not maintain the membrane fluidity level, particularly with @entity1068 -grown cells.
