Metabolic capacity of purified vesicles from Frankia EAN1pec

Abstract

The actinorhizal bacteria Frankia produce vesicles, specialized cell structures that are the site of nitrogen fixation. Vesicles were isolated and purified from Frankia strain EAN1pec grown in culture. The physiological properties of these purified vesicles were characterized with respect to their metabolic capacity and compared to that of the intact mycelium. Our results indicate that the vesicle is unable to generate ATP. When compared on a protein basis, the total adenylate nucleotide pool of intact mycelium was 10-fold higher than total pool obtained with purified vesicles. Purified vesicles exhibit low rates of endogenous respiration, about 5-fold lower than the rates obtained with intact mycelia. The addition of succinate increased vesicle respiration by 1.6-fold, but several other carbon sources had no effect on respiration. Vesicle respiration showed a degree of insensitivity to cyanide. The addition of succinate, a respirable substrate, did not increase the energy charge or ATP level of purified vesicles. In the case of intact mycelium. controls, the absence or presence of an energy source directly affected the energy charge and ATP levels. These results combined with those of previous studies indicate that the vesicles is dependent on the ATP supplied from the hyphae to which they are attached.

Publication Date

2004

Journal Title

Symbiosis

Publisher

Balaban Publishing

Scientific Contribution Number

2218

Document Type

Article

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