| Summary: | 博士 === 國立清華大學 === 生命科學系 === 96 === In Escherichia coli, the biosynthesis of lysine is generated from aspartate, and the process contains nine steps. Aspartokinase III encoded by lysC, catalyzes the first step of lysine biosynthesis. In this thesis, we generated a lysC knockout strain E. coli K-12 W3110 using汹财 red recombination system. And we inspected the global gene expression profiles between lysC knockout and wild type E. coli. Several significant differential gene expressions were observed, including the up-regulation of lysine biosynthetic pathway genes like asd, dapB and dapE. Genes related to aspartate and glutamate biosynthetic processes like ppc and gdhA were up-regulated as well. These results suggested that the lysC knockout exhibited a lysine starvation phenotype. A time series microarray analysis was carried out following the lysC knockout profiling experiment. S-(2-aminoethyl) cysteine (AEC) was added to the medium and the gene expression profiles following four time points were monitored. The results of AEC treatment time series expression analysis showed that the lysC-induced lysine starvation phenotype was neutralized by AEC. AEC affected several clusters of gene expressions, including lysine biosynthetic process, nucleotide biosynthetic process, sulfate metabolic process, transport system and stress response proteins. AEC treated lysC knockout exhibited a lysine excess phenotype by repressing the lysine biosynthetic process genes like asd, dapA, dapB, dapD and lysA. Genes related to aspartate biosynthesis like aspC and ppc and gdhA were also found down-regulated after AEC treatment. The results of this thesis help clarifying the systematic regulation of lysine biosynthesis in E. coli.
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