GLYCINE BETAINE CONFERS ENHANCED OSMOTOLERANCE AND CRYOTOLERANCE ON LISTERIA-MONOCYTOGENES
GLYCINE BETAINE CONFERS ENHANCED OSMOTOLERANCE AND CRYOTOLERANCE ON LISTERIA-MONOCYTOGENES
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DOI：
10.1128/jb.176.2.426-431.1994
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发表时间：
1994-01-01
影响因子：
3.2
通讯作者：
SMITH, GM
中科院分区：
文献类型：
--
作者：
KO, R;SMITH, LT;SMITH, GM
单核细胞增生李斯特菌是一种革兰氏阳性食源性病原体，对渗透压具有显着的抵抗力，并且可以在冰箱温度下生长。这两个特征使其成为对公共健康的潜在威胁。与其他几种生物体一样，单增李斯特氏菌在渗透胁迫下生长时，会在细胞内积累甘氨酸甜菜碱，这是一种普遍存在且有效的渗透剂。然而，当它在冰箱温度的寒冷胁迫下生长时，它也会积累甘氨酸甜菜碱。外源添加的甘氨酸甜菜碱可提高应激细胞的生长速率，但不会提高未应激细胞的生长速率，即，它赋予渗透耐受性和低温耐受性。盐刺激和冷刺激的甘氨酸甜菜碱积累都是通过培养基的转运而不是通过生物合成发生的。直接测量甘氨酸甜菜碱摄取量表明，在高盐浓度 (4% NaCl) 下，细胞转运甜菜碱的速度比不添加盐时快 200 倍，在 7 ℃ 时比在 30 ℃ 下转运甜菜碱快 15 倍。甘氨酸甜菜碱转运的动力学表明，两种转运系统在对甜菜碱的亲和力方面没有区别，并且可能是相同的。高渗休克和冷休克实验表明运输系统是本构的；氯霉素不阻断激活。冷激活运输系统是一种新颖的观察结果，对于低温下细胞膜的物理状态具有有趣的意义。
Listeria monocytogenes is a gram-positive food-borne pathogen that is notably resistant to osmotic stress and can grow at refrigerator temperatures. These two characteristics make it an insidious threat to public health. Like several other organisms, L. monocytogenes accumulates glycine betaine, a ubiquitous and effective osmolyte, intracellularly when grown under osmotic stress. However, it also accumulates glycine betaine when grown under chill stress at refrigerator temperatures. Exogenously added glycine betaine enhances the growth rate of stressed but not unstressed cells, i.e., it confers both osmotolerance and cryotolerance. Both salt-stimulated and cold-stimulated accumulation of glycine betaine occur by transport from the medium rather than by biosynthesis. Direct measurement of glycine betaine uptake shows that cells transport betaine 200-fold faster at high salt concentration (4% NaCl) than without added salt and 15-fold faster at 7 than at 30-degrees-C. The kinetics of glycine betaine transport suggest that the two transport systems are indistinguishable in terms of affinity for betaine and may be the same. Hyperosmotic shock and cold shock experiments suggest the transport system(s) to be constitutive; activation was not blocked by chloramphenicol. A cold-activated transport system is a novel observation and has intriguing implications concerning the physical state of the cell membrane at low temperature.