Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School



In the early part of this century it was observed that certain microorganisms could grow in the absence of fixed nitrogen. Since those early observations there has been an intensive effort to unravel the mystery behind the physiology of nitrogen fixation. It was not until development of the use of heavy isotopes that we begin to learn the mechanism of biological nitrogen fixation. It was the object of this study to determine if glutamate dehydrogenase (GDH) was present in A. vinelandii when it was fixing nitrogen. If it is assumed that GDH is the principal means of assimilation of NH+4 by A. vinelandii, it should be present when cells are fixing nitrogen if NH+4 is an intermediate in nitrogen fixation. If GDH were found in cells fixing nitrogen this would not be proof of its involvement in the process. However, if it were shown to be absent during nitrogen fixation and present during NH+4 assimilation, one can assume that it plays no role in nitrogen fixation. For this to be true GDH must be an inducible enzyme.

Library of Congress Subject Headings

Nitrogen -- Fixation

Azotobacter vinelandii



Number of Pages



South Dakota State University