There was up-regulation of phoBR (SO1558-59) and phoU (SO1726) genes, which regulate the phosphate transporters genes during phosphate starvation [28–32]. Up-regulated genes in response to stress conditions i.e., starvation, phage LY2606368 molecular weight infection, oxidative stress, include a stringent starvation protein encoded by the sspAB
genes (SO0611-0612), and a phage shock protein operon pspABC (SO1807-1809). Other up-regulated stress-related genes were the RNA polymerase sigma-70 factor rpoD (SO1284)[32, 35], a GTP-binding protein that regulates the TCA cycle and responds to starvation (era [SO1349]), and a DNA repair protein (recO [SO1350]). Discussion The I-BET151 results of this study demonstrate that EtrA positively regulates dissimilatory nitrate, fumarate and DMSO reduction pathways in S. oneidensis MR-1. The generation of etrA knockout mutant EtrA7-1 in the wild type strain MR-1 background eliminated any possible secondary effects on the phenotype, such as the electron transfer perturbation suspected with the rifampicin resistant DSP10 strain . Similar to other etrA mutants of strain MR-1, EtrA7-1 retained its ability to reduce nitrate [6, 7, 16]; however, our results show that the anaerobic growth of the mutant was significantly
impaired compared to the wild type when nitrate was the only electron acceptor. Likewise, the etrA deletion mutant lost its ability to reduce fumarate and DMSO with both lactate and pyruvate as electron donor. Regulation ZD1839 ic50 of DMSO reduction by EtrA in strain MR-1 was suggested previously  however this study provides physiological evidence
that confirm its role. The ability of the EtrA7-1 mutant to reduce TMAO and thiosulfate also decreased; however the reduction of Fe(III) citrate, selleck screening library Mn(IV) and sulfite was not affected by the deletion. No differences in growth performance between the wild type and the mutant were observed under aerobic conditions (data not shown). The transcriptome analysis provides a genome-wide expression profile of S. oneidensis MR-1 instead of the partial genome array that was previously evaluated (691 ORFs  vs 4,648 genes in this study). We observed in 612 (13%) differentially expressed genes represented though some are likely due to differences in growth rate between the mutant strain and the wild type strain. Nonetheless, the expression patterns of genes are consistent with the physiological data and with the transcription data reported for Fnr in E. coli [11, 12, 20] and with the more limited data by Beliaev et al. . Genes involved in nitrate reduction (napDAHGB, nrfA, and hcp) were significantly down-regulated by the etrA deletion as well as those encoding the fumarate reduction (frdAB, fccA) and all the genes encoding for the DMSO reductases (dmsAB). All of these genes have been considered candidates for EtrA regulation in previous studies; however, results were not conclusive [5–7, 16].