2l8 



H. G. WOOD, F. W. LEAVER 



VOL. 12 (1953) 



from COo is not convertible to the "Cj" from formaldehyde metabolism. It thus seems 

 likely that two different C^ compounds may play a role in the fermentation. 



NaF inhibition of CO^ utilization. It was observed by Wood and Werkman^^ 

 that NaF inhibited the net fixation of CO3 in glycerol fermentations. Accompanying 

 this, there was inhibition of succinate formation. In the fermentations of glucose, the 

 inhibition of succinate formation was not complete and it seemed possible that there 

 was a fluoride intensitive mechanism of succinate production which was independent 

 of CO2 fixation. However, it was observed in unpublished experiemnts^ (p. 149), that 

 the NaF did not prevent the incorporation of ^^COg into the carboxyl groups of propio- 

 nate and succinate during glucose or glycerol dissimilation. These observations seemed 

 of sufficient interest to warrant further investigation. The results are shown in Table IX. 

 Unfortunately, the final CO 2 collections were not quantitative due to an accident so that 

 the net CO2 fixed or produced could not be determined directly. However, it is apparent 

 from Table IX that NaF inhibited the formation of non-volatile acids. It has been 

 shown^^'^^ that in glycerol fermentations succinate is the only non-volatile acid formed 



TABLE IX 



EFFECT OF NaF ON FERMENTATION BY CULTURE 1 9 (P. shermanit) 



No. 



Substrate 



NaF 

 Present 



Substrate 

 fermented 

 niMjiooml 



Volatile 

 acid 



meg/ioo 

 mM 



substrate 



Non- 

 volatile 



acid 

 meq/ioo 



niM 

 substrate 



Non- 

 reducing 

 sugar' 

 mMjioo 



mM 

 substrate 



Initial 

 C0„ 



cpm/fiM 



Final Average „ j.- , r ■ , 

 ^Q P^ Propionate Succinate 



cpmliM cpmUiM '^'"''''^^ '^''''^'^^ 



21 Glycerol 



24 Glycerol 



25 Glucose 



26 Glucose 



No 

 Yes 

 No 

 Yes 



9-33 

 4-56 

 4.96 

 4.69 



68 



54 

 129 

 136 



44 

 4.1 



39 



6.5 



19-5 

 8.6 



25.2 

 25.2 

 25.2 

 25.2 



19.7 

 23.6 



15-2 



14.7 



22.4 

 24.4 

 20.2 

 20.0 



9-85 



4.71 



12.04 



8.86 



15.8 

 II. I 

 19.8 

 17. 1 



Fermentations were set up the same as Fermentations 20, 21, and 22 in Table VIII except that 

 when glucose was used it was 0.05 M, the NaF was 0.015 ^^^' s-^^d the cells were 2.3 %. The propionate 

 and succinate were isolated by chromatography and were oxidized to COj for radioactivity measure- 

 ment. Procedures are given in the text. The^^C distribution in the succinate, propionate and acetate of 

 Fermentation 25 is shown in Table VII. 

 * See footnote to Table I. 



and that an almost equivalent amount of COg is utilized. It is therefore quite certain 

 that NaF inhibited CO 2 utilization and succinate formation in the present experiment 

 The CO2 produced in Fermentation 21 has been calculated to be 30.3 mil/ per 100 mM 

 of glycerol. Table VIII. For this calculation the assumption was made that the net CO 2 

 fixed was equal to the succinate formed. On a similar basis it may be calculated that 

 the CO2 produced in Fermentation 24 was 16.7 mM when NaF was added. It is noted 

 that in both the glycerol and glucose fermenteitions the specific activity of the propionate 

 and succinate was reduced in the presence of NaF. 



Two possible explanations of the results are suggested. One is that there are two 

 mechanisms of fixation of CO 2 occurring simultaneously and that one of these leads to 

 a net uptake of CO 2 and formation of succinate and is inhibited by NaF, whereas the 

 second is insensitive to NaF and does not lead to a net uptake of CO 2- It is possible that 

 the fluoride sensitive mechanism involves phosphopyruvate and that NaF prevents the 

 generation of the phosphopyruvate which is essential for the fixation. This possibility 

 is attractive because Utter and Kurahashi'*^ have recently shown that the fixation of 



References p. 22IJ222. 



