In vivo study of the state of order of the membranes of gram-negative bacteria by Fourier-transform infrared spectroscopy (FT-IR).

Temperature-induced order/disorder transition profiles were obtained from the membranes of intact Gram-negative bacterial cells by FT-IR analysis of the frequency shifts of the acyl chain methylene symmetric stretching band as a monitor. Cells grown at different temperatures yielded distinct transition profiles. At the individual growth temperatures, however, the nearly alike frequency values indicated a very similar 'state of order' of the bacterial membranes. The FT-IR data were complemented by GC analysis of whole cell fatty acid composition. The FT-IR data obtained in vivo gave direct evidence of the adaptation of the 'state of order' and 'fluidity' of bacterial membranes to varying growth temperatures.