Water as the source of oxidant and reductant in bacterial chemosynthesis.

Abstract

The two vital aspects of chemoautotrophic metabolism are the generation of energy (ATP or the equivalent) and a simultaneous production of reducing power coupled to the enzymic oxidation of an inorganic substrate. Aleem and Nason' reported that in the obligately chemoautotrophic bacterial genus Nitrobacter the enzymic oxidation of nitrite is catalyzed by a cytochrome-containing electron transport particle via cytochrome c and cytochrome oxidase-like components.They subsequently demonstrated2 the coupling of this oxidation with the generation of high-energy phosphate bonds which were identified as adenosine triphosphate (ATP). The over-all reaction is:

The isotopic composition of nitrate produced from nitrification in a hardwood forest floor

“…However, the microbial end-member is not as easily determined from field samples, which usually contain a mixture of nitrate from both sources. Laboratory studies have shown that, during the conversion of ammonium to nitrate by chemolithoautotrophic bacteria, two oxygens come from water and one from O 2 (Aleem et al, 1965;Andersson and Hooper, 1983;Kumar et al, 1983;Hollocher, 1984 (Kendall, 1998).…”

Quantifying the effects of clear-cutting and strip-cutting on nitrate dynamics in a forested watershed using triple oxygen isotopes as tracers

“…During the conversion of ammonium to nitrate by chemolithoautotrophic bacteria, two oxygen atoms originate from H 2 O and one from O 2 (Aleem et al, 1965;Andersson and Hooper, 1983;Kumar et al, 1983). In recent laboratory studies, the kinetic isotope effects during incorporation of O atoms were estimated to be +20.4 ± 2.3 ‰ for ammonia oxidation (O 2 plus H 2 O incorporation) and +8.6 ± 2.3 ‰ for incorporation of H 2 O during nitrite oxidation (Buchwald et al, 2012).…”

Stable isotopic evidence for high microbial nitrate throughput in a High Arctic glacial catchment

“…The findings of Aleem et al (1965), Hollocher et al (1981), Andersson and Hooper (1983) and Kumar et al (1983) suggested that nitrification process incorporates two H 2 O-derived and one O 2 -derived oxygen atom to 385 form nitrate. Further, these studies reported no isotopic effect during oxygen incorporations or any further isotopic exchange.…”