Graduation Semester and Year

2013

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biology

Department

Biology

First Advisor

Woo-Suk Chang

Abstract

Bradyrhizobium japonicum is a nitrogen-fixing bacterium that can establish a symbiotic relationship with the soybean plant. To be a successful symbiont, B. japonicum must have an effective mechanism to deal with plant defense responses such as oxidative burst. Our previous transcriptomic study showed that carQ (bll1028) encoding extracytoplasmic function (ECF) sigma factor was highly expressed (108-fold induction) in response to Hâ‚‚Oâ‚‚-mediated oxidative stress. In this study, a carQ knock-out mutant was constructed to identify the role of carQ in the oxidative response of B. japonicum. The mutant exhibited a significant decrease in survival at 10 mM Hâ‚‚Oâ‚‚ for 10 min and distinguishable nodulation phenotypes compared to the wild type. Desiccation of mutant cells also resulted in lower percent cell survival in both early and late desiccation periods. Taken together, the findings will provide insights into how the ECF sigma factor regulates and contributes to the survival of the bacteria.

Disciplines

Biology | Life Sciences

Comments

Degree granted by The University of Texas at Arlington

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