Williams J C, Weiss E
J Bacteriol. 1978 Jun;134(3):884-92. doi: 10.1128/jb.134.3.884-892.1978.
The obligate intracellular bacterium Rickettsia typhi was examined for its ability to generate and maintain an adenylate energy charge in an extracellular environment. Freshly purified organisms were incubated, at 34 degrees C and pH 7.4, with or without glutamate and various other metabolites, and the levels of ATP, ADP, and AMP were determined. Of the metabolites tested, glutamate and glutamine were the most effective for the generation of ATP. In the presence of glutamate, there was a rapid increase in the level of ATP, followed by a moderate decrease during 150 min of incubation. The energy charge increased from a level of 0.2 to 0.5 to about 0.7 to 0.75, and then slowly declined to about 0.45 to 0.6. In the absence of glutamate, after an occasional initial surge in ATP level as the temperature was changed from 4 to 34 degrees C, there was a sharp decline in both ATP and energy charge (to 0.1 and sometimes to 0.01). The rickettsiae maintained their ability to regenerate their energy charge upon the addition of glutamate for about 30 min, but this ability declined with further incubation. In contrast to Escherichia coli, the decline in ATP in R. typhi was accompanied by a sharp increase in the level of AMP and the total adenylate pool. No adenine or adenosine was recovered from rickettsiae incubated with labeled AMP, ADP, or ATP. From these experiments and the demonstration reported elsewhere that rickettsiae transport the adenine nucleotides, it can be concluded that the adenylate energy charge in R. typhi is governed by the salvage of the adenine nucleotides rather than their unphosphorylated precursors. Thus, R. typhi undergoes greater shifts in energy charge than other bacteria, a phenomenon which may account for their instability in an extracellular environment. Under optimal conditions the adenylate energy charge of R. typhi approaches levels that border on those generally regarded as adequate for growth.
对专性细胞内细菌鼠伤寒立克次氏体在细胞外环境中产生并维持腺苷酸能荷的能力进行了检测。将新鲜纯化的菌体在34℃、pH 7.4条件下，分别与谷氨酸及其他各种代谢物一起或不与它们一起孵育，然后测定ATP、ADP和AMP的水平。在所测试的代谢物中，谷氨酸和谷氨酰胺对ATP的产生最为有效。在谷氨酸存在的情况下，ATP水平迅速升高，随后在150分钟的孵育过程中适度下降。能荷从0.2至0.5的水平升高到约0.7至0.75，然后缓慢下降至约0.45至0.6。在没有谷氨酸的情况下，当温度从4℃变为34℃时，ATP水平偶尔会出现初始激增，之后ATP和能荷都急剧下降（降至0.1，有时降至0.01）。立克次氏体在添加谷氨酸后约30分钟内保持其能荷再生能力，但随着进一步孵育，这种能力会下降。与大肠杆菌不同，鼠伤寒立克次氏体中ATP的下降伴随着AMP水平和总腺苷酸库的急剧增加。用标记的AMP、ADP或ATP孵育立克次氏体后，未回收腺嘌呤或腺苷。从这些实验以及其他地方报道的立克次氏体转运腺嘌呤核苷酸的证据可以得出结论，鼠伤寒立克次氏体中的腺苷酸能荷是由腺嘌呤核苷酸的补救合成而非其未磷酸化的前体所控制。因此，鼠伤寒立克次氏体的能荷变化比其他细菌更大，这一现象可能解释了它们在细胞外环境中的不稳定性。在最佳条件下，鼠伤寒立克次氏体的腺苷酸能荷接近通常认为足以支持生长的水平。
