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The Carbon-Quotient of Micrococcus denitri/icans Beijerinck Summary. 1. The manometric method as described by N~veke (1965) used to determine the amount of entirely assimilated carbon derived from CO 2 (~ carbonquotient) by heterotrophic bacteria was investigated for its usefulness.
Micrococcus denitri/icans it has been demonstrated that the method can lead to considerable errors if certain conditions are not observed.
The sources of error could be eliminated extensively by stabilization of the pH-value in the cell suspension and by obtaining as soon as possible the wante~l COs-partial pressure in the gas room of the Warburg-vessels.
Under the modified conditions the carbon-quotient of M. denltrificans reached the value 1.0 after oxidation of formic acid.
From this it could be concluded that tile entire carbon requirement of M. denitrificans is probably satisfied from C02 if the energy is obtained from the dehydrogenation of formic acid. 6. From the 02-saving after the oxidation of 20 ~moles formate in the presence of CO~ it could be calculated that 13,9 ~g C are thereby assimilated. The direct determination of assimilated carbon by wet combustion of the bacteria gave approximately the same result.
From this a free-energy efficiency of the formate-oxidation of about 10~ could be calculated.
Methode zur Bestimmung des aus CO S stammenden Anteils an der Gesamtkohlenstoffassimilation (= Kohlenstoffquotient) durch heterotrophe Bakterien wurde auf ihre Brauchbarkeit geprfift. 2. Am Beispiel des oxydativen Abbaues yon Formiat durch Micrococcus denitrificans konnte gezeigt werden, daB die Methode zu betr~chtlichen Fehlern fiihren kann, wenn bestimmte Bedingungen nicht eingehalten werden. 3. Durch Stabilisierung des pH-Wertcs in dcr Zellsuspension und durch mSgliehst schnelle Herstellung des gewfinschten COe-Partialdrucks im Gasraum der Warburggefii]3e konnten die Fehlerquellen weitgehend beseitigt werden. 4. Unter den ver~nderten Versuchsbedingungen erreiehte der Kohlenstoffquotient yon M. denitrificans nach der Oxydation yon Ameisens~ure den Wert 1,0. * Auszug aus dcr gleichlautenden Dissertation der Mathematisch-Naturwissenschaftlichen Fakult~t der Universit~t Hamburg 1968.
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