Regulatory links between iron metabolism and oxidative stress in Rhodobacter sphaeroides

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With the appearance of oxygen on earth reactive oxygen species appeared and iron availability was drastically decreased. Iron potentiates oxygen toxicity by the production of hydroxyl radicals in the Fenton reaction. Thus life in the presence of oxygen requires a strict regulation of iron metabolism and its coupling with regulation of the oxidative stress defense. Iron-sulfur clusters are also important redox-sensing elements of proteins. Our previous work revealed many links of oxidative stress to iron metabolism in Rhodobacter sphaeroides. Therefore we want to use this established phototrophic model organism to further elucidate the regulation of iron metabolism in an alpha proteobacterium and its link to the oxidative stress defense. We will identify regulatory factors that affect expression of genes for iron metabolism in response to oxidative stress and iron limitation or excess. In parallel we will investigate the role of known or predicted iron and redox regulators in these responses. The available data on mRNA levels and protein synthesis rates in the wild type will be complemented by studies in mutant strains and by in vitro studies in order to elucidate the mechanisms of regulation by the individual proteins and regulatory RNAs. The metabolic versatility of R. sphaeroides allows to discriminate between direct effects of iron and secondary effects caused by oxidative stress and to analyze the impact of photosynthetic complexes. These studies will thus provide new insights into the co-regulation of iron metabolism and oxidative stress defense in bacteria.