C. Seifritz et al., NITRATE AS A PREFERRED ELECTRON SINK FOR THE ACETOGEN CLOSTRIDIUM-THERMOACETICUM, Journal of bacteriology, 175(24), 1993, pp. 8008-8013
Nitrate enhanced the vanillin- and vanillate-dependent growth of Clost
ridium thermoaceticum. Under nitrate-enriched conditions, these aromat
ic substrates were subject to 0 demethylation. However, acetate, the n
ormal product obtained from 0 demethylation, was not detected. Acetate
was also not detected when methanol and CO cultures were supplemented
with nitrate; glucose cultures likewise produced approximately one-th
ird less acetate when enriched with nitrate. Reductant derived from th
e oxidation of these substrates was recovered in nitrite and ammonia.
With an ammonia-limited medium employed to evaluate N turnover, the fo
llowing stoichiometry was observed concomitantly with the consumption
of 2.0 mM 0-methyl groups (the recovery of nitrate-derived N approxima
ted 89%): 3.9 mM NO3- --> 2.8 mM NO2- +0.7 mM NH3. The results demonst
rated that (i) nitrate was preferentially used as an electron sink und
er conditions that were otherwise acetogenic, (ii) nitrate dissimilati
on was energy conserving and growth supportive, and (iii) nitrate-coup
led utilization of O-methyl groups conserved more energy than acetogen
ic O demethylation.