CONTROL OF BACTERIAL RESPIRATION BY INORGANIC ORTHOPHOSPHATE

II. "Pi-EFFECT" AND BACTERIAL OXIDATIVE PHOSPHORYLATION

Abstract

An inorganic orthophosphate-activation of resting respiration in the intact cells of Brevibacterium ammoniagenes, tentatively named the "Pi-effect", was further investigated in comparison with oxidative phosphorylation.
The "Pi-effect" was very susceptible to chemical modification of cell structure and completely arrested by lysozyme treatment. Five mM of MgCl₂ protected the "Pi-effect" from lysozyme, though it could not repress an increase in cellular permeability of NADH caused by lysozyme. Efficiency of phosphorylation to respiration determined both in vivo and in vitro was almost unchanged by lysozyme treatment.
The ratios of Pi/O, which was calculated by a method similar to that for ADP/O, and P/O in vivo and in vitro were about 0, 0.05, and 0.1 to NADH, respectively, and 1.0, 0.25, and 0.8 to succinate, respectively.
Inhibitors and uncouplers such as p-quinone, menadione, arsenate, o- phenanthroline, pentachlorophenol, and tributyltin chloride, which markedly reduced the efficiency of oxidative phosphorylation, also acted to abolish the "Pi-effect" without exception.