Global transcriptional analysis of Geobacter sulfurreducens under palladium reducing

Geobacter sulfurreducens is capable of reducing Pd(II) to Pd(0) using pyruvate as an electron donor; however, the biochemical and genetic mechanisms involved in this process have not been described. In this work, we carried out transcriptome profiling analyes to identify genes involved in Pd(II) reduction in this bacteria. Our results showed that 254 genes were upregulated while 142 were downregulated during Pd(II) reduction. Among the upregulated genes, 12 were related to energy metabolism and electron transport; 50 were classified as involved in protein synthesis; 42 were associated with regulatory functions and transcription, and 47 have no homologs with known function. RT-qPCR data confirmed upregulation during Pd(II) reduction of genes encoding PilA, the structural protein for the electrically conductive pili, and c-type cytochromes GSU1062, GSU2513, GSU2808, GSU2934, GSU3107, OmcH, OmcM, PpcA, PpcD. ?pilA and ?pilR mutant strains showed 20% and 40%, decrease in the Pd(II) reduction respectively, compared to the wild type strain, indicating the central role of the pili in this process. RT-qPCR data also confirmed downregulation during Pd(II) reduction of the omcB, omcC, omcZ, and omcS genes, which have been shown to be involved in Fe(III) reduction and electrodes. Based on these results, we propose mechanisms involved in Pd(II) reduction by G. sulfurreducens. Overall design: mRNA profiles of Geobacter sulfurreducens in Pd(II) reduction or NBAF medium, in duplicate, using Illumina Genome Analyzer Iix