Date of Award


Degree Type


Degree Name

Master of Science




Dr. Wenze Li

Second Advisor

Dr. Mark Bernards

Third Advisor

Dr. Krzysztof Szczyglowski


Chlamydomonas reinhardtii strain Dark Blue 6 (DB6) was isolated following random insertional mutagenesis, due to its inability to assimilate nitrate. DB6 lacks terminal nitrate reductase activity and xanthine dehydrogenase activity, indicating that it is deficient in the molybdenum cofactor (Moco) required for those two enzymes. The inability of DB6 to grow on a nitrate medium is partially rescued when it is cultured in a medium containing high concentrations of molybdate. This distinct attribute, termed molybdate repair, is typically associated with mutants defective in molybdate transport or the insertion of molybdenum into the Moco pterin precursor. The molybdenum content in DB6 cells is significantly lower than that of the control strain, indicating that molybdate uptake may be affected. Genetic complementation with a variety of candidate genes, including known and potential molybdate transporters, was unable to recover wild-type phenotype. Based on this initial characterization, DB6 appears to be a novel Moco deficient mutant of C. reinhardtii defective in molybdate transport, and may provide additional insight into the terminai steps of Moco biosynthesis.



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