Transcriptional response to elemental sulfur in Geobacter sulfurreducens

The metal-reducing bacterium Geobacter sulfurreducens PCA is capable of anaerobic respiration using elemental sulfur as an electron acceptor. Despite 3 decades since its isolation, the molecular mechanisms underlying sulfur respiration remain unclear. In this study, we conducted a transcriptome analysis of G. sulfurreducens PCA cultured with and without sublimed sulfur. In the presence of sulfur, 153 genes were significantly up-regulated, while 599 genes were down-regulated. Notably, genes encoding redox proteins involved in energy conservation, particularly multiheme c-type cytochromes, exhibited altered expression patterns. In addition, elemental sulfur induced the transcription of genes associated with sulfur, selenium, and nitrogen metabolism, as well as protein redox homeostasis, DNA repair, and even cell motility. These transcriptional responses may reflect metabolic adaptation to sulfur respiration, redox state alterations, and sulfur-induced stress. Our findings uncover a complex regulatory landscape governing sulfur respiration and provide critical insights into this long-standing biochemical enigma in G. sulfurreducens PCA.