Project description:To investigate the protein components of Shewanella oneidensis wild-type (WT) and mutant strains (Δfur, ΔssoR, ΔfurΔssoR) under threshold iron-limiting conditions, we collected samples from these strains and performed 4D labelfree proteomics analysis for each sample.
Project description:Initial attachment to a surface marks the onset of a bacterial life style switch from planktonic to biofilm mode of growth. Among dissimilatory iron reducing bacteria, S. oneidensis MR-1 is notable due to its extensive respiratory versatility. It has been hypothesized that direct interaction of Shewanella cells with, or close proximity to, an appropriate surface facilitates the deposition of electrons. In fact, Shewanella species have been demonstrated to adhere to various surfaces and form biofilms. Global transcriptome profiling was performed on cells in the transition to surface-associated growth using different surfaces and conditions to understand molecular mechanisms underlying the initiation of microbe-surface interactions and the switch from planktonic to sessile life style. In the study presented, expression profiles of two independent replicates of Shewanella oneidensis MR-1 wild type cells attached to glass for 0.25 h and 1 h, respectively, under hydrodynamic conditions were compared to two independent replicates of planktonic grown Shewanella oneidensis MR-1 wild type cells. Furthermore, expression profiles of two independent replicates of Shewanella oneidensis MR-1 wild type cells attached for 1 h to iron surface under hydrodynamic conditions were compared to two independent replicates of Shewanella oneidensis MR-1 wild type cells attached to glass for 1 h. All samples were obtained from aerobically grown cells in LM.
Project description:Time-series transcriptional profiles of Shewanella oneidensis type strain MR-1 under iron depletion and repletion conditions. Iron homeostasis of Shewanella oneidensis, a gamma-proteobacterium possessing high iron content, is regulated by a global transcription factor Fur. However, knowledge is incomplete about other biological pathways that respond to changes in iron concentration, as well as details of the responses. In this work, temporal gene expression profiles were examined for iron depletion and repletion to delineate the iron response of S. oneidensis and a gene co-expression network was reconstructed. Modules of iron acquisition systems, anaerobic energy metabolism and protein degradation were the most noteworthy in the gene network. Bioinformatics analyses suggested that genes in each of the modules might be regulated by DNA-binding proteins Fur, CRP and RpoH, respectively. Closer inspection of these modules revealed a transcriptional regulator (SO2426) involved in iron acquisition and ten transcriptional factors involved in anaerobic energy metabolism. Selected genes in the network were analyzed by genetic studies. Disruption of genes encoding a putative alcaligin biosynthesis protein (SO3032) and a gene previously implicated in protein degradation (SO2017) led to severe growth deficiency under iron depletion conditions. Disruption of a novel transcriptional factor (SO1415) caused deficiency in both anaerobic iron reduction and growth with thiosulfate or TMAO as an electronic acceptor, suggesting that SO1415 is required for specific branches of anaerobic energy metabolism pathways. In conclusion, we identified major biological pathways that were differentially expressed during iron depletion and repletion.
Project description:Time-series transcriptional profiles of Shewanella oneidensis type strain MR-1 under iron depletion and repletion conditions. Iron homeostasis of Shewanella oneidensis, a gamma-proteobacterium possessing high iron content, is regulated by a global transcription factor Fur. However, knowledge is incomplete about other biological pathways that respond to changes in iron concentration, as well as details of the responses. In this work, temporal gene expression profiles were examined for iron depletion and repletion to delineate the iron response of S. oneidensis and a gene co-expression network was reconstructed. Modules of iron acquisition systems, anaerobic energy metabolism and protein degradation were the most noteworthy in the gene network. Bioinformatics analyses suggested that genes in each of the modules might be regulated by DNA-binding proteins Fur, CRP and RpoH, respectively. Closer inspection of these modules revealed a transcriptional regulator (SO2426) involved in iron acquisition and ten transcriptional factors involved in anaerobic energy metabolism. Selected genes in the network were analyzed by genetic studies. Disruption of genes encoding a putative alcaligin biosynthesis protein (SO3032) and a gene previously implicated in protein degradation (SO2017) led to severe growth deficiency under iron depletion conditions. Disruption of a novel transcriptional factor (SO1415) caused deficiency in both anaerobic iron reduction and growth with thiosulfate or TMAO as an electronic acceptor, suggesting that SO1415 is required for specific branches of anaerobic energy metabolism pathways. In conclusion, we identified major biological pathways that were differentially expressed during iron depletion and repletion. Four biological replicates of S. oneidensis MR-1 cells were grown to the midlog phase (OD600 = 0.6). Samples were collected at time 0, and then at 1, 5, 10, 20, 40, and 60 min after adding 2,2'-dipyridyl to attain a final concentration of 160 uM. Thereafter, ferrous sulfate was added to final concentration of 200 uM, and cells were collected at 1, 5, 10, 20, 40, and 60 min.
Project description:Shewanella oneidensis is an important model organism for bioremediation studies because of its diverse respiratory capabilities. In recent years, biofilm development of S. oneidensis has been extensively studied because it is essential to reduce solid metals. As a special form of biofilm, however, pellicles are largely overlooked. The goal of this work was to understand requirements of S. oneidensis pellicle formation and the molecular basis of pellicle formation. We demonstrated that successful pellicle formation and survival was likely to require the threshold level of cell density and higher concentration of oxygen. Proteinase K and EDTA were potent pellicle disrupter. DNA microarray experiments were used to study the gene expression profile of young air–liquid interface pellicle relative to planktonic cells, which indicated that the air–liquid interface pellicle was more metabolically active than the planktonic cells. Most notably, consistently up-regulation of iron or heme uptake and transportation proteins was observed in the S. oneidensis MR-1 pellicle. However, neither the hmuT nor hugA heme transport mutant was defective in pellicle formation. An examination of the influence of several metal cations on the anti-pellicle activity of EDTA showed that Ca (II), Mn(II), Cu(II), and Zn(II) fully protected S. oneidensis MR-1 pellicle against EDTA treatment while additional of iron enabled the initiation of pellicle formation but maturation was significantly impaired. Collectively, iron was less important than other metals with respect to pellicle formation in S. oneidensis.
Project description:Comparative RNA-Seq profiling of Sideroxydans sp. CL21, a microaerophilic, Fe(II)-oxidizer, and the facultative anaerobe Shewanella oneidensis, an Fe(III) reducer. The microorganisms were grown in co-culture and monoculture batch incubations under microaerobic growth conditions. RNA-Seq profiling was used to compare the transcriptomes of both Sideroxydans sp. CL21 and S. oneidensis when grown in co-culture compared to growth in monoculture
Project description:Transcriptomic analysis used to understand the influence of elevated intracellular cyclic-di-GMP in Shewanella oneidensis on expression of c-type cytochrome at transcript level.
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: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:Initial attachment to a surface marks the onset of a bacterial life style switch from planktonic to biofilm mode of growth. Among dissimilatory iron reducing bacteria, S. oneidensis MR-1 is notable due to its extensive respiratory versatility. It has been hypothesized that direct interaction of Shewanella cells with, or close proximity to, an appropriate surface facilitates the deposition of electrons. In fact, Shewanella species have been demonstrated to adhere to various surfaces and form biofilms. Global transcriptome profiling was performed on cells in the transition to surface-associated growth using different surfaces and conditions to understand molecular mechanisms underlying the initiation of microbe-surface interactions and the switch from planktonic to sessile life style.