Author

Jing Zhang

Publication Date

2014

Document Type

Honors Thesis

Department

Biochemistry

Keywords

Molecular biology, Microbiological synthesis, Polyketides, Genetic regulation, Clostridium, Electrophysiology, Acetogen, Gene regulation, Electrobiocommodity (E-BC)

Abstract

Microbial electrosynthesis is an efficient and sustainable strategy that directly supplies electrons to cathode biofilms to yield transportation fuel and a diversity of organic commodities. Clostridium ljungdahlii represents a favorable platform organism for microbial electrosynthesis, due to its ability to grow autotrophically, its genetic tractability and the ability to engineer C. ljungdahlii to produce desirable organic compounds. In this study, genes encoding a two-component signal transduction system (CLJU_c28870-28880), and a gene encoding a transcription factor( CLJU_c34750) were investigated for their involvement in the autotrophic growth of C. ljungdahlii. Mutants deficient for these genes exhibited slightly slower growth patterns, decreased production of acetate and enhanced ethanol production compared to the wild-type strain under both autotrophic growth on H2/CO2 and heterotrophic growth on fructose. This result demonstrates the dispensable effects of these genes on carbon assimilation under the autotrophic condition, and the connection of the Wood-Ljungdahl pathway and the Embden-Meyerhof-Parnas (EMP) pathway when C. ljungdahlii were grown heterotrophically. The third gene investigated in this study, CLJU_c11220, encodes a homolog of Spo0A in C. ljungdahlii, which functions as a global regulator controlling gene expression during sporulation and biofilm formation in Bacillus and a number of Clostridium species. The deletion of this gene resulted in noticeable changes in colony morphology and biofilm architecture. Trans expression of gene CLJU_c11220 restored colony morphology back to that of the wild-type strain. The effects the Spo0A homolog deletion in C. ljungdahlii was further studied at a whole transcriptome level. The RNA-seq results revealed a pleiotropic role of Spo0A in the regulation of genes from a wide array of functional classes, and resulted in the down-regulation of expression of flagellar, chemotaxis and sporulation process genes. Our limited knowledge of the genes decision I made, and helped me push through the tides against my family's occupational currents. This project was supported by the Advanced Research Projects Agency-Energy (ARPA-E), 419, U.S. Department of Energy.

Language

English

Comments

viii, 91 pages : illustrations (chiefly color). Honors Project-Smith College, 2014. Includes bibliographical references (pages 84-91)

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