Project description:Cyclic 3',5'-adenosine monophosphate (cAMP) phosphodiesterase (CPD) is an enzyme that catalyzes the hydrolysis of cAMP, a signaling molecule affecting diverse cellular and metabolic processes in bacteria. Some CPDs are also known to function in cAMP-independent manners, while their physiological roles remain largely unknown. Here, we investigated physiological roles of CPD in Shewanella oneidensis MR-1, a model environmental bacterium, and report that CPD is involved in amino-acid metabolism. We found that a CPD-deficient mutant of MR-1 (ΔcpdA) showed decreased expression of genes for the synthesis of methionine, S-adenosylmethionine, and histidine and required these three compounds to grow in minimal media. Interestingly, deletion of adenylate cyclases in ΔcpdA did not restore the ability to grow in minimal media, indicating that the amino acid requirements were not due to the accumulation of cAMP. These results suggest that CPD is involved in the regulation of amino acid metabolism in MR-1 in a cAMP-independent manner.
Project description:Comparisson of expression profiling of a etrA deletion mutant strain (experimental sample) with that of the wild type Shewanella oneidensis MR-1 strain to assess global direct/indirect genetic regulation EtrA in Shewanella oneidensis MR-1 shares 73.6% and 50.8% amino acid sequence identity with the oxygen-sensing regulator Fnr in E. coli and Anr in Pseudomonas aeruginosa, respectively; however, its regulatory role of anaerobic metabolism in Shewanella spp. is complex and not well understood. Whole-genome expression profiling using a etrA gene deletion mutant as the experimental sample and the wild type strain as the reference, determine that EtrA fine-tunes the expression of genes involved in various anaerobic metabolic pathways, including nitrate, fumarate and dimethyl sulfoxide reduction. Moreover, genes involved in prophage activation and and genes implicated in aerobic metabolism were also differentially expressed. In contrast to previous studies that attributed a minor regulatory role to EtrA in Shewanella spp., this study demonstrates that EtrA acts as a global transcriptional regulator and cofers physiological advantages to the strain under certain growth conditions.
Project description:We investigated the anode-specific responses of Shewanella oneidensis MR-1, an exoelectroactive ammaproteobacterium, using for the first time iTRAQ and 2D-LC MS/MS driven membrane proteomics to compare protein abundances in S. oneidensis when generating power in MFCs, and growing in a continuous culture.
Project description:The sumitted data compares gene expression profile of Shewnaella oneidensis MR-1 on two different sets of media conditions (nutritionally rich LB medium and Lactate minimal medium) To explore the effect of various growth phases in Shewanella oneidensis MR-1, the genome-wide transcriptome profiles growth in two sets media was compared to each other. Strain was grown in chemostat at 20% O2 in batch culture. Samples were collected in duplicate from both experiments.
Project description:Comparison of gene expression and mutant fitness in Shewanella oneidensis MR-1 Expression data for 15 growth conditions in mid-exponential phase and expression data across growth phases for 3 of those conditions
Project description:To identify the transcriptional targets of the DNA-binding response regulator HnoC (SO_2540), mRNA transcript levels in Shewanella oneidensis were measured using whole genome microarray analysis. Transcript levels were compared between WT Shewanella oneidensis and a hnoC deletion strain.
Project description:Shewanella oneidensis MR-1 is a facultative anaerobe that grows by respiration using a variety of electron acceptors. This organism serves as a model to study how bacteria thrive in redox-stratified environments. A glucose-utilizing engineered derivative of MR-1 has been reported to be unable to grow in glucose minimal medium (GMM) in the absence of electron acceptors, despite this strain having a complete set of genes for reconstructing glucose to lactate fermentative pathways. To gain insights into why MR-1 is incapable of fermentative growth, this study examined a hypothesis that this strain is programmed to repress the expression of some carbon metabolic genes in the absence of electron acceptors. Comparative transcriptomic analyses of the MR-1 derivative were conducted in the presence and absence of fumarate as an electron acceptor, and these found that the expression of many genes involved in carbon metabolism required for cell growth, including several tricarboxylic acid (TCA) cycle genes, was significantly downregulated in the absence of fumarate. This finding suggests a possibility that MR-1 is unable to grow fermentatively on glucose in minimal media owing to the shortage of nutrients essential for cell growth, such as amino acids. This idea was demonstrated in subsequent experiments that showed that the MR-1 derivative fermentatively grows in GMM containing tryptone or a defined mixture of amino acids. We suggest that gene regulatory circuits in MR-1 are tuned to minimize energy consumption under electron acceptor-depleted conditions, and that this results in defective fermentative growth in minimal media. IMPORTANCE It is an enigma why S. oneidensis MR-1 is incapable of fermentative growth despite having complete sets of genes for reconstructing fermentative pathways. Understanding the molecular mechanisms behind this defect will facilitate the development of novel fermentation technologies for the production of value-added chemicals from biomass feedstocks, such as electro-fermentation. The information provided in this study will also improve our understanding of the ecological strategies of bacteria living in redox-stratified environments.
Project description:This study presents a global transcriptional analysis of the cold shock response of Shewanella oneidensis MR-1 after a temperature downshift from 30 to 8 or 15oC based on time-series microarray experiments. More than 700 genes were found to be significantly affected (p < 0.05) upon cold shock challenge, especially at 8oC. The temporal gene expression patterns of the classical cold-shock genes varied and only some of them, most notably so1648 and so2787, were differentially regulated in response to temperature downshift. The global response of S. oneidensis to cold shock was also characterized by the up-regulation of genes encoding membrane proteins, DNA metabolism and translation apparatus components, metabolic proteins, regulatory proteins, and hypothetical proteins. Most of the metabolic proteins affected are involved in catalytic processes that generate NADH or NADPH. Keywords: time course, stress response
Project description:We combined high-resolution tiling microarrays and 5'-end RNA sequencing to obtain a genome-wide map of transcription start sites (TSSs) for Shewanella oneidensis MR-1. To test the reliability of these TSSs, we compared our result to those from differential RNA sequencing (dRNA-seq), which discriminates primary and processed ends of transcripts. We found that our identified TSSs tend to have significantly more mapped reads in the TEX(+) sample than the TEX(-) sample. Overall, the dRNA-seq results support the validity of our predictions for TSS. S. oneidensis MR-1 was grown to mid-log phase in Luria-Bertani broth (LB) or defined lactate minimal medium, and total RNA was isolated and used for differential RNA-sequencing (dRNA-seq) by next-generation sequencing, which is used to verify genome-wide transcription start sites. For dRNA-seq, total RNA was partially treated with Terminator Exonuclease (TEX) to digest processed RNA and thereby enrich for primary transcript ends.