Insights into Systems for Iron-Sulfur Cluster Biosynthesis in Acidophilic Microorganisms.

Fe-S clusters are versatile and essential cofactors that participate in multiple and fundamental biological processes. In , the biogenesis of these cofactors requires either the housekeeping Isc pathway, or the stress-induced Suf pathway which plays a general role under conditions of oxidative stress or iron limitation. In the present work, the Fe-S cluster assembly Isc and Suf systems of acidophilic Bacteria and Archaea, which thrive in highly oxidative environments, were studied. This analysis revealed that acidophilic microorganisms have a complete set of genes encoding for a single system (either Suf or Isc). In acidophilic Proteobacteria and Nitrospirae, a complete set of genes (), but not genes coding for the Suf system, was detected. The activity of the Isc system was studied in sp. CF-1 (Nitrospirae). RT-PCR experiments showed that eight candidate genes were co-transcribed and conform the operon in this strain. Additionally, RT-qPCR assays showed that the expression of the gene was significantly up-regulated in cells exposed to oxidative stress imposed by 260 mM Fe(SO) for 1 h or iron starvation for 3 h. The activity of cysteine desulfurase (IscS) in CF-1 cell extracts was also up-regulated under such conditions. Thus, the Isc system from sp. CF-1 seems to play an active role in stressful environments. These results contribute to a better understanding of the distribution and role of Fe-S cluster protein biogenesis systems in organisms that thrive in extreme environmental conditions.