Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/Miguel Servet, 177, 50013, Zaragoza, Spain.
Int J Food Microbiol. 2009 Nov 15;135(3):274-80. doi: 10.1016/j.ijfoodmicro.2009.07.010. Epub 2009 Jul 17.
The role of sigmaB in the Staphylococcus aureus heat-shock induced thermotolerance was investigated. Survival curves at 58 degrees C of S. aureus strain Newman and its isogenic DeltasigB mutant were obtained for native and heat-shocked cells (45 degrees C for 5-120 min) in exponential and stationary phase of growth. The magnitude of the acquisition of thermotolerance at 58 degrees C depended on the growth phase and on the duration of the heat shock. Stationary growth phase cells were always more heat tolerant than exponentially growing cells and thermotolerance increased with heat-shock duration up to 120 min. S. aureus cells were able to increase their heat tolerance in the absence of the sigma(B) factor. In stationary phase, whereas in the parental strain the thermotolerance was increased by a factor of 12 after a heat shock of 120 min at 45 degrees C (delta values at 58 degrees C for native and heat-shocked cells were 0.63 and 7.22 min, respectively), in the mutant strain it increased 43 fold (delta values 0.09 and 3.87 min). The addition of chloramphenicol to the adaptation medium resulted in a lower increase in heat tolerance but did not prevent it completely, suggesting that S. aureus can partially increase its thermotolerance without "de novo" protein synthesis. Both the number of non-damaged cells and the proportion of cells able to repair sublethal damage were higher for heat-shocked cells.
研究了西格玛 B 在金黄色葡萄球菌热休克诱导耐热性中的作用。对野生型金黄色葡萄球菌菌株 Newman 及其同源缺失突变株 DeltasigB 在指数生长期和稳定生长期中，用 58°C 的存活曲线对原生和热休克（45°C 5-120min）细胞进行检测。在 58°C 时获得耐热性的程度取决于生长阶段和热休克的持续时间。与指数生长期细胞相比，稳定生长期细胞始终具有更高的耐热性，且耐热性随热休克时间的延长而增加，最高可达 120min。金黄色葡萄球菌细胞在缺乏 sigma(B) 因子的情况下也能够提高其耐热性。在稳定生长期，在野生型菌株中，45°C 热休克 120min 后，耐热性提高了 12 倍（原生和热休克细胞在 58°C 时的 delta 值分别为 0.63 和 7.22min），而在突变株中，耐热性提高了 43 倍（delta 值分别为 0.09 和 3.87min）。在适应培养基中加入氯霉素会导致耐热性增加减少，但不会完全阻止，这表明金黄色葡萄球菌可以在没有“从头开始”的蛋白质合成的情况下部分提高其耐热性。与未受热休克的细胞相比，受热休克的细胞中非损伤细胞的数量和能够修复亚致死损伤的细胞的比例都更高。
