微量热法研究环境NaCl浓度对盐生盐杆菌生长代谢的影响

Microcalorimetric Study of the Influence of Extracellular NaCl Concentration on the Growth Metabolism of Halobacterium halobium

采用TAMair微量热系统和安瓿法测定了盐生盐杆菌在不同NaCl浓度中生长的生长产热曲线,拟合得到盐生盐杆菌在不同NaCl浓度中生长的热动力学方程和热动力学参数,并分析了盐生盐杆菌生长的各种热动力学参数与环境NaCl浓度的关系.由此发现,盐生盐杆菌生长的最适NaCl浓度并不是传统认为的一个宽泛的范围——3.5mo·lL-1至约5.2mo·lL-1(NaCl饱和),而是约3.9mo·lL-1.在环境NaCl浓度由3.9mo·lL-1逐步升高至饱和的过程中,盐生盐杆菌的生长代谢持续减弱.进一步的透射电镜观察发现在近饱和的NaCl浓度中生长的盐生盐杆菌细胞发生了质壁分离,较好地解释了微量热研究的结果.由此对NaCl浓度变化导致嗜盐古生菌表面结构改变提出了新的解释.

Microcalorimetry was used to study the influence of extracellular NaCl concentration on the growth metabolism of Halobacterium halobium （Hbt. halobium） using a TAM air isothermal microcalorimeter. The metabolic thermogenic curves of Hbt. halobium growth in different concentrations of NaCl were obtained using the ampoule method. The thermokinetic equations and parameters of Hbt. halobium growth were calculated and the relationship between each thermokinetic parameter and the concentration of NaCl was obtained. The results showed that the optimum NaCl concentration for Hbt. halobium growth was not a wide range from 3.5 mol L-1 to about 5.2 mol·L-1 （NaCl saturation）, as is generally acknowledged, but just around 3.9 mol·L-1. For an extracellular NaCl concentration above 3.9 mol·L-1, the growth metabolism of Hbt. halobium decreased constantly with an increase in the NaCl concentration. Further investigation by transmission electron microscopy revealed that the Hbt. halobium cells growing in approaching NaCl saturation underwent plasmolysis, which interpreted the finding of microcalorimetry perfectly. All these results led to a new interpretation of the structural transformations of Hbt. halobium upon NaCl concentration altering.