Díaz-Acosta Alondra, Sandoval María L, Delgado-Olivares Luis, Membrillo-Hernández Jorge
Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, Mexico City, Mexico.
Arch Microbiol. 2006 Jun;185(6):429-38. doi: 10.1007/s00203-006-0113-9. Epub 2006 May 6.
The natural living style of Escherichia coli occurs in the gastrointestinal tract, where most of its existence is spent under anaerobic conditions and in stationary phase of growth. Here we report on the heat shock response of E. coli K-12 cells growing in the presence or absence of oxygen. An rpoH mutant (impaired in the synthesis of the sigma(32) transcriptional factor) exhibited an increased sensitivity to heat shock but only in the exponential phase of aerobic growth, suggesting that in anaerobic growth conditions, and in aerobic stationary phase, sigma(32)-independent mechanisms are playing a prime role in protecting cells from heat stress. Our results demonstrated that sigma(S) is not involved in this protection system. Studies on the kinetics of synthesis of Heat shock proteins (Hsp) after an abrupt rise in temperature demonstrated that in the absence of oxygen, the synthesis of Hsp is triggered faster and is sustained for a longer period of time compared to aerobic growth conditions. Finally, the heated cells in the exponential phase of aerobic growth displayed a high concentration of oxidatively damaged proteins in the presence of 4 mM H(2)O(2), in sharp contrast to cultures of stationary phase or anaerobic growth.
大肠杆菌的自然生存方式发生在胃肠道中，其大部分时间处于厌氧条件下且处于生长的稳定期。在此，我们报告了在有氧或无氧条件下生长的大肠杆菌K - 12细胞的热休克反应。一个rpoH突变体（在σ32转录因子的合成中受损）对热休克表现出更高的敏感性，但仅在有氧生长的指数期如此，这表明在厌氧生长条件以及有氧稳定期，不依赖σ32的机制在保护细胞免受热应激方面起主要作用。我们的结果表明σS不参与这个保护系统。对温度突然升高后热休克蛋白（Hsp）合成动力学的研究表明，与有氧生长条件相比，在无氧条件下，Hsp的合成触发更快且持续时间更长。最后，在有氧生长指数期的加热细胞在4 mM H2O2存在的情况下显示出高浓度的氧化损伤蛋白，这与稳定期或厌氧生长的培养物形成鲜明对比。
