Investigation of the Fur regulon in G. sulfurreducens

Iron is an essential element in bacteria as a result of being commonly used as a cofactor. In G. sulfurreducens, the assimilatory need for iron is especially high as a result of up to 111 coding sequences for c-type cytochromes, many of which have multiple heme-binding sites. It may also be necessary for G. sulfurreducens to carefully regulate its iron uptake and transport as a result of its environmental iron concentrations constantly being in flux. Thus, the direct transcriptional role of a key iron-dependent regulator known as the ferric uptake regulator (Fur) was investigated in G. sulfurreducens through expression profiling of a variety of iron conditions via microarray analysis in combination with binding sites elucidated via chromatin immunoprecipitation coupled with microarrays (ChIP-chip). 224 genes were determined according to the ChIP-chip binding profile to be directly regulated by Fur, and 22 of these genes overlapped with differential expression observed in expression profiling. From this study, Fur was determined to be the primary regulator of genes involved in iron uptake and transport as well as a key regulatory of several other genes that play key roles in G. sulfurreducens. The implications of this study also provide a commentary on the methods generally used to determine the genome-wide role of transcriptional regulations as well as the complexity of transcriptional regulatio