Regulatory response of methanogen cells to different forms of iron and sulfur

We used comparative transcriptomics to explore cellular responses to growth on pyrite (FeS2) or aqueous iron (Fe(II)) and sulfur (cysteine or sulfide). Transcriptomic data from wild type M. barkeri identified subset of genes that was significantly upregulated during grown on FeS2 versus ferrous iron and cysteine or sulfide. Several of these genes, including a membrane-bound hydrolase, alpha-keto reductases, and flavin mononucleotide-dependent flavodoxin reductases were highly conserved among known FeS2-reducing methanogens and were located in a single gene cassette. Putative enzymatically catalyzed mechanisms of FeS2 reduction are proposed for each of these enzyme systems to guide their future biochemical and biophysical study. Transcriptomic data from wild type M. barkeri identified subset of genes that was significantly upregulated during grown on FeS2 versus ferrous iron and cysteine or sulfide. Several of these genes, including a membrane-bound hydrolase, alpha-keto reductases, and flavin mononucleotide-dependent flavodoxin reductases were highly conserved among known FeS2-reducing methanogens and were located in a single gene cassette. Putative enzymatically catalyzed mechanisms of FeS2 reduction are proposed for each of these enzyme systems to guide their future biochemical and biophysical study. Overall design: Methanosarcina barkeri strain MS cells were grown with three different sources of iron and sulfur: 20 uM ferrous iron and 2mM cysteine, 20 uM ferrous iron and 2 mM sulfide, or 2 mM pyrite (FeS2). Total mRNA from mid-log phase cells from four replicate for each condition were sequenced.