Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Carl A. Westby


The intensive study of A. brasilense that has been undertaken is due in part to the desire of microbiologists to understand its nitrogen metabolism. A. brasilense can perform all of the reactions of the nitrogen cycle except for nitrification, however, the details are not yet completely understood on any of the processes. In agriculture, A. brasilense not only supplies fixed nitrogen and nutrient to cereals; but also it significantly contributes to the loss of nitrogen from the soil by denitrification. Enormous amounts of fixed nitrogen are unfortunately lost from the soil to the atmosphere by this denitrification. The elucidation of the interrelationship between nitrogen-fixation and denitrification in this organism will therefore be of great importance. Globally, the No3- metabolism of A. brasilense lessens or adds to human health problems (ozone removal from stratosphere, blue baby syndrome, N03- as carcinogen). Thus, an overall understanding of N03 metabolism in A. brasilense will be of enormous benefit to human kind My study examined N03- and No2- assimilation in A. brasilense and assimilation of purine nitrogen. Various A. brasilense mutants defective in N03- or N02- assimilation were isolated and characterized, and revertants were obtained and studied. In addition, the N03-/N02- assimilation of two recombinant E. coli strains containing a 27 kb segment of A. brasilense DNA (in a cosmid) was also studied.

Library of Congress Subject Headings


Escherichia coli

Nitrogen cycle




Number of Pages



South Dakota State University