A Global approach to the hydrogen production, carnon assimilation and nitrogen metabolism of rhodobacter capsulatus by physiological and microarray analyses

Afşar, Nilüfer
One of the most important parameters affecting hydrogen production in photofermentation process is the type of carbon and nitrogen sources. For this reason in this research, the effect of different nitrogen sources (5mM ammonium chloride and 2mM glutamate) and acetate concentrations (40‐80mM) on metabolism of Rhodobacter capsulatus were investigated. First of all, physiological experiments were carried out to compare growth, hydrogen production and substrate utilization behaviors of R. capsulatus on different nitrogen sources and acetate concentrations. For further understanding of hydrogen production, carbon assimilation and nitrogen metabolism; microarray analysis were conducted. For this purpose, an Affymetrix GeneChip for R. capsulatus was custom designed and manufactured. An efficient RNA isolation protocol from R. capsulatus was optimized for use of microarray analysis. Validation of the microarray experiments and custom designed R. capsulatus were carried out by RT‐qPCR analysis. On 5mM ammonium chloride containing medium, transcription of genes related to transport, assimilation and utilization of acetate were significantly up‐regulated compared to 2mM glutamate medium. On the other hand, nitrogenase enzyme encoding genes were significantly down‐regulated on ammonium chloride containing medium. Although transcription of genes that take role in acetate assimilation did not show a significant difference on 80mM acetate compared to 40mM acetate; TCA cycle, photosynthetic apparatus, electron transport and Calvin cycle related genes were significantly down‐regulated on 80mM acetate. From microarray data analysis results, it was suggested for the first time that Rhodobacter capsulatus might assimilate acetate by using two different routes using glyoxylate cycle and/or ethylmalonyl‐CoA pathway.


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Citation Formats
N. Afşar, “A Global approach to the hydrogen production, carnon assimilation and nitrogen metabolism of rhodobacter capsulatus by physiological and microarray analyses,” Ph.D. - Doctoral Program, Middle East Technical University, 2012.