ATP metabolism in Streptococcus mutans

(1)鼠链球菌，一种b型突变链球菌，在厌氧葡萄糖限制恒化器中培养，以测定葡萄糖的摩尔生长产率，最大生长产量和维持系数来自葡萄糖的吸收和计算的ATP产生作为pH的函数。此外，在酸性条件下生长的细胞和在中性pH下生长的细胞中都存在F_1F_0型H^+-ATPase。结果表明，该有机体通过牺牲一些能量成本来响应和适应环境酸化，在葡萄糖利用效率和在中性pH下高效地继续生物质生产所需的额外维护方面。(2)对变形链球菌FA-1对乙醇的细胞响应进行了动力学测量。乙醇产酸是绝对需要氧气的，这导致细胞内ATP浓度(ATP_1)从饥饿水平显著增加到一个稳定水平，该水平在介质中存在氧气的情况下保持不变。氧耗尽后，ATP_1立即恢复到饥饿状态。稳定的ATP_1和伴随耗氧率都是乙醇浓度的函数。

(1) Streptococcus rattus, a serotype b strain of mutants streptococci, was grown in an anaerobic gulcose-limited chemostat to determine the molar grown yield of glucose, the maximum growth yields and maintenance coefficients form glucose uilizition and calculated ATP generation as a function of pH.Also examined was the presence of an F_1F_0-type H^+-ATPase in cells grown under acidic conditions and in cells grown at neutral pH.The results suggest that the organism responds and adapts to environmental acidification by sacrificing some energy cost in terms of both the efficiency of glucose utilization to generate ATP and the extra maintenance required to continue biomass production ad efficiently as under neutral pH.(2) Kinetic measurements were made of the cellular responses of S.mutans FA-1 to ethanol. Oxygen was absolutely required for acid production from ethanol, which elicited a marked increase in the intracellular ATP concentration (ATP_1) from a starved level to a steady level which was held constant as long as oxygen was present in the medium. Once oxygen was exhausted, ATP_1 returned to the starved level without delay. Both the steady ATP_1 and the rate of accompanying oxygen consumption were functions of the ethanol concentration.