ATP metabolism in Streptococcus mutans

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(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.