An examination of proton translocation and energy conservation during heterotrophic nitrification

Abstract

Whether selected heterotrophic nitrifiers, as do the autotrophs, conserve energy during the oxidation of their nitrogenous substrates was studied. The examinatio of proton translocation of four different bacterial nitrifiers capable of pyruvic oxime [(PO), CH 3C(NOH)COOH] nitrification and by an NH 4 + oxidizing Arthrobacter sp. was initiated. Three of the PO nitrifying bacteria, all pseudomonads, oxidize hydroxylamine (NH 2OH) at a greater rate than PO and yielded only stoichiometric protons when NH 2OH was the reductant. The fourth bacterium, Alcaligenes faecalis ATCC 8750, an adept PO oxidizer, does not appreciably oxidize NH 2OH. The bacterium displayed å N +NH 2OH ratios for less than if NH 2OH was stoichiometrically converted to nitrite. When given NH 4 +, the Arthrobacter sp. yielded proton translocation patterns which were inconsistent with the metabolic data collected concerning NH 4 + oxidation. Thus no data was collected which supported energy conservation via proton translocation by these heterotrophic nitrifiers.