Ribonucleotide reductases (RNRs) are essential enzymes that are involved in DNA synthesis. While this makes them ideal targets for antiproliferative drugs, most known RNR targeting agents are nonspecific. This poses a problem when considering antimicrobials, but several groups of bacteria have RNRs that utilize unique mechanisms that could be exploited if fully understood. One such bacteria, Flavobacterium johnsoniae, has the gene for a class Id RNR with a novel activation mechanism. Class Id RNRs belong to the aerobic class I RNRs and seem to have a unique metallocofactor and activation mechanism involving superoxide and manganese. The goal of this research was to demonstrate how this mechanism functions in vivo. To accomplish this, we created thirty-three mutant strains of F. johnsoniae, deleting either of the RNR genes (F. johnsoniae also has genes for class Ia) as well as genes to influence levels of superoxide, hydrogen peroxide, and manganese. Growth and gene expression of these mutants were then analyzed to determine the function of class Id. We have determined that both Id and Ia are functional in F. johnsoniae, and that Ia is primarily expressed in the wild type strain. However, when Ia is deleted, expression of Id rises to compensate. We have also determined a relationship between the class Id RNR and both hydrogen peroxide and superoxide. Cells that are utilizing the Id enzyme seem to tolerate both oxygen species better than cells utilizing Ia. While no in vivo relationship with manganese was determined for the either Id or Ia, we have not ruled out that possibility.


Yongtao Zhu

Committee Member

J. Martin Bollinger

Committee Member

Allison Land

Date of Degree




Document Type



Master of Science (MS)

Program of Study



Biological Sciences


Science, Engineering and Technology

Available for download on Tuesday, November 18, 2025



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