Cold shock in Bacillus subtilis: different effects of benzyl alcohol and ethanol on the membrane organisation and cell adaptation

Abstract

A temperature shift-down of Bacillus subtilis from 40 to 20 degrees C induces an 80 min growth lag. Benzyl alcohol reduced this period to 51 min, whereas ethanol prolonged it up to 102 min. The effect of the two alcohols on the membrane state was investigated by measuring the steady-state fluorescence anisotropy and analysing the lifetime distribution of diphenylhexatriene (DPH) and its polar derivative, TMA-DPH. As followed from the fluorescence anisotropy, the two alcohols exerted similar (fluidizing) effects on the cytoplasmic membranes of B. subtilis. However, benzyl alcohol significantly shortened the main DPH lifetime component and widened its distribution, while ethanol had no effect. The benzyl alcohol activity was interpreted in terms of an increased membrane hydration due to disordering of the membrane structure. Such an effect imitates the cold shock induced synthesis of unsaturated fatty acids in B. subtilis. The fatty acid analysis revealed that ethanol hindered this adaptive synthesis of fatty acids. At the same time, its effect on the membrane state (membrane order) was very low and could not substitute the physiological response as was the case with benzyl alcohol. It can thus be concluded that the adaptation of the membrane physical state contributes significantly to the cold shock response of B. subtilis.

Pentanol and Benzyl Alcohol Attack Bacterial Surface Structures Differently

“…Laurdan is an environmentally sensitive probe, and the associated spectral shift reflected a change in membrane polarity (27). For BzA, its addition has been reported to cause a disordered membrane structure (35,43). Our data indicated that a nonlethal concentration of BzA also caused disorder of membrane structures, suggesting that the structural change could increase the permeability of BAC to accelerate BAC accumulation in cells.…”

“…They induced interdigitation in the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membrane (39,40), causing an increase in proton permeability (41,42). In a Bacillus subtilis strain, the lethal concentration of BzA increased the membrane fluidity (43). For protein structures, BzA induced the aggregation of proteins, such as human interleukin (44) and interleukin-1 receptor antagonist (45), by partially unfolding these proteins (46,47).…”

Global Transcriptional Analysis of Virus-Host Interactions between Phage ϕ29 and Bacillus subtilis

“…However, 29 induced genes showed a significant overlap (P Ͻ 0.01 [two-sided Fisher exact test]) compared to those repressed by cold stress when cells suffer a temperature downshift from 37 to 18°C. Since the B. subtilis cold shock response leads to a growth lag as a consequence of the inhibition of RNA, DNA, and protein synthesis (65), it could be expected that bacterial genes induced by 29, which requires the host machinery to promote its multiplication, were repressed under such conditions. On the other hand, there is an interesting correlation (P Ͻ 0.005 [two-sided Fisher exact test]) between downregulated genes after 29 infection and genes induced when glycerol or gluconate are the carbon sources used by the bacteria, suggesting a phage repression of the metabolism of a broad range of alternative carbon sources.…”

Cyclopropanation of Membrane Unsaturated Fatty Acids Is Not Essential to the Acid Stress Response of Lactococcus lactis subsp. cremoris

“…First, we observed a disappearance of anteiso-C 15:0 in favor of iso-C 15:0 for the three strains. The growth-dependent changes in the ratio of terminally branched iso and anteiso fatty acids were suggested in Bacillus subtilis as mechanisms to adjust fluidity (25,31,34) without a change in the saturation level of membrane fatty acids. Second, an accumulation of palmitoleic acid in the wild-type and mutant strains cultivated in the presence of ethanol was obtained (17% [molar percentage] versus 2.5% with acid-grown cells).…”