| Summary: | 碩士 === 國立臺灣大學 === 分子與細胞生物學研究所 === 96 === Rhodopseudomonas palustris (R. palustris), a purple nonsulfur bacteria, is among the most metabolically versatile bacteria and ubiquitous in soil and water. The microbe could use sunlight, organic or inorganic compound for cellular energy, and use atmosphere carbon dioxide, or green plant-derived compound for cell material. It also could produce hydrogen gas by biological nitrogen fixation. The microbe could adjust and reweave itself in response to changes in light, carbon, nitrogen and electron sources. The ability of R. palustris to use carbon dioxide depends on two metabolic states: photoautotrophic and chemoautotrophic state. In this study, we used microarray for transcriptomic study, and two-dimensional polyacrylamide gel electrophoresis and mass spectrometry for proteomic study, respectively. Our results showed that 1357, 2512, 1629, 168 genes were differentially expressed over two-fold in photoautotrophic verus chemoautotrophic conditions, chemoautotrophic versus chemoheterotrophic conditions, photoautotrophic versus photoheterotrophic conditions, and chemoheterotrophic versus photoheterotrophic conditions, respectively. We identified 38 proteins differentially expressed over two-fold between two of the four major metabolic states. Some proteins, such as 60kDa chaperonin 2, ABC transporter related proteins, phosphoenolpyruvate carboxykinase, catalase, and phosphoglycerate dehydrogenase, could differentially expressed in three of these four major metabolic states. Interestingly, ABC transporter pathway was related to switch of autotroph and heterotroph. With computational prediction of plausible protein-protein interactions among these 38 proteins, we found 60kDa chaperonin 2, transcription terminator rho, acyl-CoA dehydrogenase, S-adenosylmethionine synthetase, alcohol dehydrogenase were the hub proteins in the predicted interaction network. These findings help us understand the regulatory mechanism of R. palustris.
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