Sébastien Zappa
Postdoctoral Researcher Associate

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Curriculum vitae (English)
Curriculum vitae (French)

My research focuses on the regulation of the synthesis of tetrapyrroles in Rhodobacter capsulatus SB1003. This strain is a model of purple a-proteobacteria capable of growing in a broad range of environmental conditions: aerobically, microaerobically, anaerobically, heterotrophically, phototrophically, etc… In order to cope with changes in the environment, it synthesizes three major tetrapyrroles in a finely-tuned manner. These three products are: cobalamine (vitamine B12), involved in the synthesis of aminoacids and bacteriochlorophyll; heme, involved in a lot of cellular process such as gas-carrying, redox-sensing, cell signaling; and bacteriochlorophyll, involved in light-harvesting during photosynthesis. These molecules can be seen as end-products of three branches of the same tree. Their respective synthesis share a common trunk, which is universal, and diverge later into specific synthesis steps. The whole pathway involves a total of approximately 35 enzymes and their harmonious coordination as a respond to the cell needs requires the setup of a fine regulation system, including several transcription factors. Several of them have been studied for a long time in the lab, such as RegA, FnrL, CrtJ, AerR; mostly with regard to the regulation of photosynthesis, but the study of their involvement in other tetrapyrrole branches is being undertaken. In addition, some “newer” transcription factor, namely HbrL and Irr, have kept me busy in the recent years. Indeed, their involvement in the regulation of heme synthesis is being investigated, along with influence of potential cofactors such as iron.