Ultee A, Kets E P, Alberda M, Hoekstra F A, Smid E J
Agrotechnological Research Institute (ATO-DLO), Wageningen, The Netherlands.
Arch Microbiol. 2000 Oct;174(4):233-8. doi: 10.1007/s002030000199.
Carvacrol, a natural antimicrobial compound present in the essential oil fraction of oregano and thyme, is bactericidal towards Bacillus cereus. A decrease of the sensitivity of B. cereus towards carvacrol was observed after growth in the presence of non-lethal carvacrol concentrations. A decrease of the melting temperature (Tm) of membranes from 20.5 degrees C to 12.6 degrees C was the immediate effect of the addition of carvacrol. Cells adapted to 0.4 mM carvacrol showed a lower membrane fluidity than nonadapted cells. Adaptation of 0.4 mM carvacrol increased the Tm from 20.5 degrees C to 28.3 degrees C. The addition of carvacrol to cell suspensions of adapted B. cereus cells decreased Tm again to 19.5 degrees C, approximately the same value as for the non-adapted cells in the absence of carvacrol. During adaptation, changes in the fatty acid composition were observed. The relative amount of iso-C13:0, C14:0, and iso-C15:0 increased and cis-C16:1 and C18:0 decreased. The head-group composition also changed, two additional phospholipids were formed and one phospholipid was lacking in the adapted cells. It could be concluded that B. cereus adapts to carvacrol when present at non-lethal concentrations in the growth medium by lowering its membrane fluidity by changing the fatty acid and headgroup composition.
香芹酚是牛至和百里香精油成分中的一种天然抗菌化合物，对蜡样芽孢杆菌具有杀菌作用。在非致死浓度的香芹酚存在下生长后，观察到蜡样芽孢杆菌对香芹酚的敏感性降低。添加香芹酚的直接作用是使细胞膜的熔解温度（Tm）从20.5℃降至12.6℃。适应0.4 mM香芹酚的细胞比未适应的细胞表现出更低的膜流动性。适应0.4 mM香芹酚可使Tm从20.5℃升高至28.3℃。向适应香芹酚的蜡样芽孢杆菌细胞悬液中添加香芹酚，Tm又降至19.5℃，与不存在香芹酚时未适应细胞的Tm值大致相同。在适应过程中，观察到脂肪酸组成发生了变化。异-C13:0、C14:0和异-C15:0的相对含量增加，顺式-C16:1和C18:0减少。头部基团组成也发生了变化，适应细胞中形成了另外两种磷脂，并且缺少一种磷脂。可以得出结论，当生长培养基中存在非致死浓度的香芹酚时，蜡样芽孢杆菌通过改变脂肪酸和头部基团组成来降低其膜流动性，从而适应香芹酚。
