Fe(III) reduction by irradiated <i>S</i>. <i>oneidensis</i> MR-1.

<p>Cultures of <i>S</i>. <i>oneidensis</i> (MR-1) were grown aerobically in tryptic soy broth (30°C; 130 rpm) to late log–early stationary phase. Biomass was harvested and washed twice in sterile 30 mM sodium bicarbonate buffer prior to irradiation with 50 Gy X-radiation (rad). Immediately after irradiation, cell suspensions were driven anoxic with an 80:20 gas mix of N2:CO2 prior to inoculation into an anoxic medium containing 20 mM lactate as electron donor, 50 mM Fe(III) as poorly crystalline insoluble Fe(III) oxide and 30 mM sodium bicarbonate. 10 μM riboflavin (Rf) was added to media post-irradiation as an electron shuttle where necessary. Fe(II) concentrations were determined by ferrozine assay after extraction with 0.5 N HCl. Error bars depict standard error of the mean of triplicate experiments.</p

Growth, survival and extension of lag phase in X-irradiated cultures of <i>S</i>. <i>oneidensis</i> MR-1.

<p>(A) Growth profiles of aerobic cultures of <i>S</i>. <i>oneidensis</i> MR-1 (30°C) after exposure to 12, 24, 48, 72 and 95 Gy X-radiation (0.79 Gy min^-1). Irradiations began at t = 0. A minimal growth medium was used, based on that described previously [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131249#pone.0131249.ref032" target="_blank">32</a>]. Data points show mean of triplicate batch cultures and error bars depict 95% confidence intervals. (B) Mean time difference in lag phase duration between irradiated cultures and respective controls (measured at mid exponential phase). Error bars depict 95% confidence intervals from three biological replicates. (C) Survival of <i>S</i>. <i>oneidensis</i> MR-1 exposed to acute doses of X-radiation. Cultures were irradiated in the growth medium described above, serially diluted in phosphate buffered saline and plated on to solid growth medium (same as above with 1.5% agar). Error bars depict standard error of the mean CFU mL^-1.</p

Radiation induced changes to proteins in cultures of X-irradiated <i>S</i>. <i>oneidensis</i> MR-1.

<p>Mean MALDI-MS spectra of <i>S</i>. <i>oneidensis</i> MR-1 exposed to (A) 12 Gy X-radiation and (B) 95 Gy X-radiation. Spectra have been offset in the <i>y</i>-axis so that spectral features are clearly visible. Asterisks (*) show mass peaks in irradiated spectra that are discriminant with respect to batch controls, as observed in difference spectra (mean irradiated spectrum minus mean control spectrum) (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131249#pone.0131249.s007" target="_blank">S7 Fig</a>). The mass range has been limited in the figure to only include peaks which are discriminant and to which tentative annotations can be assigned, displayed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131249#pone.0131249.t001" target="_blank">Table 1</a>.</p

Partial least squares regression analysis of FT-IR spectra from control and irradiated cultures of <i>S</i>. <i>oneidensis</i> MR-1.

<p>Scores for the first two principal components (PC1 and PC2) extracted during partial least squares regression analysis performed on FT-IR data of control and X-irradiated cultures at lag phase. Solid black circles represent control samples and crosses represent irradiated samples. The nine replicates from each treatment are formed from three experimental replicates from each biological replicate.</p

Cluster analysis of spectra from irradiated and control cultures of <i>S</i>. <i>oneidensis</i> MR-1.

<p>Euclidean distances between cluster centres of control and irradiated sample discriminant function scores extracted during principal component-discriminant function analysis (PC-DFA) applied to (A) FT-IR spectra and (B) MALDI mass spectra of lag, exponential and stationary phase X-irradiated and control cultures. Principal components 1 to 5 (FT-IR) and 1 to 30 (MALDI-MS) were used by the DFA algorithm with <i>a priori</i> knowledge of machine replicates, i.e. 1 class per sample point and treatment, giving 6 classes in total for each dose.</p

The Impact of γ Radiation on the Bioavailability of Fe(III) Minerals for Microbial Respiration

Conservation of energy by Fe­(III)-reducing species such as <i>Shewanella oneidensis</i> could potentially control the redox potential of environments relevant to the geological disposal of radioactive waste and radionuclide contaminated land. Such environments will be exposed to ionizing radiation so characterization of radiation alteration to the mineralogy and the resultant impact upon microbial respiration of iron is essential. Radiation induced changes to the iron mineralogy may impact upon microbial respiration and, subsequently, influence the oxidation state of redox-sensitive radionuclides. In the present work, Mössbauer spectroscopy and electron microscopy indicate that irradiation (1 MGy gamma) of 2-line ferrihydrite can lead to conversion to a more crystalline phase, one similar to akaganeite. The room temperature Mössbauer spectrum of irradiated hematite shows the emergence of a paramagnetic Fe­(III) phase. Spectrophotometric determination of Fe­(II) reveals a radiation-induced increase in the rate and extent of ferrihydrite and hematite reduction by <i>S. oneidensis</i> in the presence of an electron shuttle (riboflavin). Characterization of bioreduced solids via XRD indicate that this additional Fe­(II) is incorporated into siderite and ferrous hydroxy carbonate, along with magnetite, in ferrihydrite systems, and siderite in hematite systems. This study suggests that mineralogical changes to ferrihydrite and hematite induced by radiation may lead to an increase in bioavailability of Fe­(III) for respiration by Fe­(III)-reducing bacteria

Expression of Flag-Pol β in MEFs and tissues from Pol β Tg mice.

<p>(A) Specificity of mouse and human qRT-PCR analysis for Pol β expression: RNA was isolated from WT and Pol β KO MEFs and MEFs expressing the Flag-Pol β transgene, as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0006493#s4" target="_blank">Methods</a> section. The relative level of expression of both the mouse (open bars) and human (filled bars) Pol β mRNA (normalized to mouse β-actin) was determined using mouse and human specific Taqman assays. Expression across samples was normalized to the expression level in the WT/Flag-Pol β MEF sample. (B) Expression of the human Pol β transgene in mouse tissues and tumors: RNA was isolated from the sample indicated in the plot, as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0006493#s4" target="_blank">Methods</a> section. The relative level of expression of human Pol β mRNA (open bars; normalized to mouse β-actin) was determined using human specific Taqman assays as in panel A. Expression across samples was normalized to the expression level in the Tg Brain sample.</p

Decreased expression of Pol β in human esophageal adenocarcinoma.

<p>(A) Photomicrograph of sections of esophageal adenocarcinoma and esophageal squamous mucosa stained for Pol β expression by immunohistochemistry. Top images reflect magnification×40 and the inserts depict magnification×100. (B) Bar graph representing relative expression level of Pol β in various tumors (stippled, open bars) and pathologically normal (grey bars) epithelial tissues. Immunoreactivity Score is the average of 5 different tumor samples each evaluated in two independent analyses.</p

Representative photomicrographs (H & E stain) of lenticular and glomerular damages in Pol β Tg mice.

<p>(A) Mature cataract characterized by degeneration/necrosis (liquefaction) and vacuolar formation in lens fibers (magnification×20). (B) High-magnification of figure a. Irregular proliferation of spindle lens fiber cells without production of normal lens fibers; necrosis and calcification are present (magnification×400). (C) Glomerular hyalinization with basement membrane thickening of Bowman's capsule, basophilic tubules, and tubular vacuolation in the renal cortex (magnification×400). (D) Glomerular hypercellularity with basement membrane thickening (magnification×400).</p

Incidence of non-neoplastic & neoplastic proliferative lesions in DNA polymerase β Tg mice.

*<p>Frequency defined as the number of animals with the lesion divided by the number of animals with the tissue examined histopathologically, multiplied by 100. Data derived from 15 males and 21 females except where noted. No neoplastic changes were detected in gallbladder, parathyroid, thymus, ileum, cecum, colon, pancreas, brain, eye, urinary bladder, testis, epididymis, prostate, seminal vesicle, oviduct, vagina, and mammary gland.</p