OM3 and WT growth in cumene hydroperoxide or at high temperature (A) 0.3 mM cumene hydroperoxide, (B) 48°C.

<p>Cells were grown in LB-kanamycin at 37°C, 200 rpm under above stressors. Each data point is the mean of three replicates.</p

MOESM1 of Improving Saccharomyces cerevisiae ethanol production and tolerance via RNA polymerase II subunit Rpb7

Additional file 1: Table S1. Primers used in plasmid construction and error-prone PCR. Table S2. Primers used in qRT-PCR. Table S3. Comparison between DNA microarray and qRT-PCR results on selected genes from M1 after 12h VHG fermentation. Figure S1. Ethanol profile with varying initial glucose supply under VHG fermentation. Figure S2. Ethanol profile with varying initial pH under VHG fermentation. Figure S3. PDC activity in M1 and the control after 12h VHG fermentation

Enhancing <em>E. coli</em> Tolerance towards Oxidative Stress via Engineering Its Global Regulator cAMP Receptor Protein (CRP)

<div><p>Oxidative damage to microbial hosts often occurs under stressful conditions during bioprocessing. Classical strain engineering approaches are usually both time-consuming and labor intensive. Here, we aim to improve <em>E. coli</em> performance under oxidative stress <em>via</em> engineering its global regulator cAMP receptor protein (CRP), which can directly or indirectly regulate redox-sensing regulators SoxR and OxyR, and other ∼400 genes in <em>E. coli</em>. Error-prone PCR technique was employed to introduce modifications to CRP, and three mutants (OM1∼OM3) were identified with improved tolerance <em>via</em> H₂O₂ enrichment selection. The best mutant OM3 could grow in 12 mM H₂O₂ with the growth rate of 0.6 h⁻¹, whereas the growth of wild type was completely inhibited at this H₂O₂ concentration. OM3 also elicited enhanced thermotolerance at 48°C as well as resistance against cumene hydroperoxide. The investigation about intracellular reactive oxygen species (ROS), which determines cell viability, indicated that the accumulation of ROS in OM3 was always lower than in WT with or without H₂O₂ treatment. Genome-wide DNA microarray analysis has shown not only CRP-regulated genes have demonstrated great transcriptional level changes (up to 8.9-fold), but also RpoS- and OxyR-regulated genes (up to 7.7-fold). qRT-PCR data and enzyme activity assay suggested that catalase (<em>katE</em>) could be a major antioxidant enzyme in OM3 instead of alkyl hydroperoxide reductase or superoxide dismutase. To our knowledge, this is the first work on improving <em>E. coli</em> oxidative stress resistance by reframing its transcription machinery through its native global regulator. The positive outcome of this approach may suggest that engineering CRP can be successfully implemented as an efficient strain engineering alternative for <em>E. coli</em>.</p> </div

Intracellular ROS level in OM3 and WT with cells treated with or without 4 mM H₂O₂.

<p>Mid exponential phase grown cells (OD₆₀₀ 0.6) were incubated with 10 µm H₂DCFDA (dissolved in dimethyl sulfoxide) at 30°C, 200 rpm. The oxidized fluorophore was quantified using excitation wavelength 485 nm and emission wavelength 528 nm. Each data point is the mean of five independent observations.</p

Cell growth in the absence or presence of H₂O₂ (A) 0 mM H₂O₂, (B) 8 mM H₂O₂, (C) 12 mM H₂O₂,

<p>Cells were cultured in LB-kanamycin medium at 37°C, 200 rpm. Each data point is the mean of three replicates.</p

DNA microarray data of certain endogenous genes in OM3 (<i>p</i><0.05, Log₂ Fold Change>2.0).

*<p>- Analyzed by qRT-PCR (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051179#pone.0051179.s011" target="_blank">Table S4</a>).</p

DNA microarray data of certain genes in OM3 after H₂O₂ treatment (<i>p</i><0.05, Log₂ Fold Change>2.0).

*<p>- Analyzed by qRT-PCR (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051179#pone.0051179.s011" target="_blank">Table S4</a>).</p

Cell growth profile after the introduction of 12 mM H₂O₂ during mid log phase (OD₆₀₀ 0.65).

<p>Each data point is the mean of three replicates.</p

Amino acid mutations in OM3.

<p>The main carbonyl of F69 interacts with the amine group of R123. The guanidium group of R82 has the electrostatic interaction with the phosphate group of cAMP. V139 is in the hinge region that participates in the inter-domain interaction between N-terminal cAMP binding domain and the C-terminal DNA binding domain. The structural stereoview was prepared by PyMOL using native CRP structure as template (PDB: 1G6N).</p

Cobalt Phosphate–ZnO Composite Photocatalysts for Oxygen Evolution from Photocatalytic Water Oxidation

Cobalt based oxygen evolution catalysts (Co–Pi) were loaded on the surface of ZnO by photochemical deposition in a neutral phosphate buffer solution containing Co²⁺ ions. Structural, morphological, and optical properties of the samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectra techniques. The Co–Pi phase formed was amorphous and was deposited on the surface of ZnO uniformly as a layer of nanoparticles. The enhanced activity for oxygen evolution was directly observed from photocatalytic water oxidation over Co–Pi loaded ZnO. The oxygen produced in the first hour was more than 4 times of that obtained over ZnO alone. The results suggest that Co–Pi played the role of cocatalyst, which can trap photogenerated holes, leading to the enhancement of electron and hole separation efficiency. Further studies showed that the mixture of cobalt phosphate and ZnO exhibited similar enhancement in activity for oxygen evolution which could be due to the oxidation of nonactive cobalt­(II) phosphate to active Co–Pi with higher oxidation states of cobalt upon light illumination during photocatalytic water oxidation process. In both systems, ZnO photocorrosion was observed based on inductively coupled plasma, XRD, and FESEM analyses