TABLE 2.

Effect of acid adaptation and acid challenge on the cell membrane FA composition of early-stationary-phase L. casei ATCC 334a

FA or parameterMean % of each FA species in total cytoplasmic membrane lipid pool ± SEM after treatment
ControlAA10AA20AA10-ACAA20-AC
C14:03.7 ± 0.540.0 ± 0.139.0 ± 1.136.0 ± 1.120.0 ± 0.3
C16:1n(9)0.6 ± 0.33.3 ± 0.12.0 ± 0.03.0 ± 0.05.8 ± 1.0
C16:015.0 ± 0.122.0 ± 0.127.0 ± 0.130.0 ± 0.125.0 ± 0.3
C17:0(9c)0.6 ± 0.5BQLbBQL1.9 ± 0.04.2 ± 1.8
C18:1n(9)41.0 ± 0.37.6 ± 0.07.0 ± 0.16.8 ± 0.011.0 ± 0.1
C18:1n(11)23.0 ± 1.38.1 ± 0.07.0 ± 0.07.7 ± 0.08.3 ± 2.6
C18:01.3 ± 1.11.7 ± 0.0BQLBQL15.0 ± 0.6
C19:0(11c)5.0 ± 3.117.0 ± 0.018.0 ± 0.115.0 ± 0.115.0 ± 2.2
% Cyclopropanec5.6171816.919.2
% Saturatedd2680848379
% Unsaturatede6519161725
Saturated/unsaturated ratio0.44.25.34.93.2
  • a Cells were propagated at pH 6.0 and then acid adapted by incubation for 10 min (AA10) or 20 min (AA20) at pH 4.5 or acid adapted for 10 or 20 min and then acid challenged at pH 2.0 for 140 min (AA10-AC or AA20-AC, respectively).

  • b BQL, below quantifiable limit (0.002%).

  • c Percentage of cyclopropane FAs [C17:0(9c) and C19:0(11c)] in the membrane.

  • d Percentage of saturated FAs [C14:0, C16:0, C17:0(9c), C18:0, and C19:0(11c)] in the membrane.

  • e Percentage of unsaturated FAs (C16:1 and C18:1) in the membrane.