Roles of RpoN in the resistance of Campylobacter jejuni under various stress conditions

<p>Abstract</p> <p>Background</p> <p><it>Campylobacter jejuni </it>is a leading foodborne pathogen worldwide. Despite the fastidious nature of <it>C. jejuni </it>growth, increasing numbers of human campylobacteriosis suggest that <it>C. jejuni </it>may possess unique mechanisms to survive under various stress conditions. <it>C. jejuni </it>possesses only three sigma factors (FliA, RpoD, and RpoN) and lacks stress-defense sigma factors. Since FliA and RpoD are dedicated to flagella synthesis and housekeeping, respectively, in this study, we investigated the role of RpoN in <it>C. jejuni</it>'s defense against various stresses.</p> <p>Results</p> <p>Survivability of an <it>rpoN </it>mutant was compared with the wild-type <it>C. jejuni </it>under various stress conditions. While the growth of the <it>rpoN </it>mutant was as comparably as that of the wild type in shaking cultures, the <it>rpoN </it>mutant exhibited significant survival defects when cultured statically. The <it>rpoN </it>mutant was more sensitive to osmotic stress (0.8% NaCl) with abnormally-elongated cell morphology. Compared to the wile type, the <it>rpoN </it>mutant was more susceptible to acid stress (pH 5) and more resistant to hydrogen peroxide. However, the <it>rpoN </it>mutation had little effect on the resistance of <it>C. jejuni </it>to alkaline pH, heat, cold and antimicrobials.</p> <p>Conclusions</p> <p>The results demonstrate that RpoN plays an important role in <it>C. jejuni</it>'s defense against various stresses which this bacterial pathogen may encounter during transmission to and infection of humans.</p

The stability of graphene band structures against an external periodic perturbation; Na on Graphene

We report that the $\pi$ band of graphene sensitively changes as a function of an external potential induced by Na especially when the potential becomes periodic at low temperature. We have measured the band structures from the graphene layers formed on the 6H-SiC(0001) substrate using angle-resolved photoemission spectroscopy with synchrotron photons. With increasing Na dose, the $\pi$ band appears to be quickly diffused into background at 85 K whereas it becomes significantly enhanced its spectral intensity at room temperature (RT). A new parabolic band centered at $k\sim$1.15 \AA$^{-1}$ also forms near Fermi energy with Na at 85 K while no such a band observed at RT. Such changes in the band structure are found to be reversible with temperature. Analysis based on our first principles calculations suggests that the changes of the $\pi$ band of graphene be mainly driven by the Na-induced potential especially at low temperature where the potential becomes periodic due to the crystallized Na overlayer. The new parabolic band turns to be the $\pi$ band of the underlying buffer layer partially filled by the charge transfer from Na adatoms. The five orders of magnitude increased hopping rate of Na adatoms at RT preventing such a charge transfer explains the absence of the new band at RT.Comment: 6 pages and 6 figure

Combining Human Umbilical Cord Blood Cells With Erythropoietin Enhances Angiogenesis/Neurogenesis and Behavioral Recovery After Stroke

Disruption of blood flow in the brain induces stroke, the leading cause of death and disability worldwide. However, so far the therapeutic options are limited. Thus, the therapeutic efficacy of cell-based approaches has been investigated to develop a potential strategy to overcome stroke-induced disability. Human umbilical cord blood cells (hUCBCs) and erythropoietin (EPO) both have angiogenic and neurogenic properties in the injured brain, and their combined administration may exert synergistic effects during neurological recovery following stroke. We investigated the therapeutic potential of hUCBC and EPO combination treatment by comparing its efficacy to those of hUCBC and EPO alone. Adult male Sprague-Dawley rats underwent transient middle cerebral artery occlusion (MCAO). Experimental groups were as follows: saline (injected once with saline 7 d after MCAO); hUCBC (1.2 × 107 total nucleated cells, injected once via the tail vein 7 d after MCAO); EPO (500 IU/kg, injected intraperitoneally for five consecutive days from 7 d after MCAO); and combination of hUCBC and EPO (hUCBC+EPO). Behavioral measures (Modified Neurological Severity Score [mNSS] and cylinder test) were recorded to assess neurological outcomes. Four weeks after MCAO, brains were harvested to analyze the status of neurogenesis and angiogenesis. In vitro assays were also conducted using neural stem and endothelial cells in the oxygen-glucose deprivation condition. Performance on the mNSS and cylinder test showed the most improvement in the hUCBC+EPO group, while hUCBC- and EPO-alone treatments showed superior outcomes relative to the saline group. Neurogenesis and angiogenesis in the cortical region was the most enhanced in the hUCBC+EPO group, while the findings in the hUCBC and EPO treatment alone groups were better than those in the saline group. Astrogliosis in the brain tissue was reduced by hUCBC and EPO treatment. The reduction was largest in the hUCBC+EPO group. These results were consistent with in vitro assessments that showed the strongest neurogenic and angiogenic effect with hUCBC+EPO treatment. This study demonstrates that combination therapy is more effective than single therapy with either hUCBC or EPO for neurological recovery from subacute stroke. The common pathway underlying hUCBC and EPO treatment requires further study

Consequences of aneuploidy in human fibroblasts with trisomy 21

An extra copy of chromosome 21 causes Down syndrome, the most common genetic disease in humans. The mechanisms contributing to aneuploidy-related pathologies in this syndrome, independent of the identity of the triplicated genes, are not well defined. To characterize aneuploidy-driven phenotypes in trisomy 21 cells, we performed global transcriptome, proteome, and phenotypic analyses of primary human fibroblasts from individuals with Patau (trisomy 13), Edwards (trisomy 18), or Down syndromes. On average, mRNA and protein levels were increased by 1.5-fold in all trisomies, with a subset of proteins enriched for subunits of macromolecular complexes showing signs of posttranscriptional regulation. These results support the lack of evidence for widespread dosage compensation or dysregulation of chromosomal domains in human autosomes. Furthermore, we show that several aneuploidy-associated phenotypes are present in trisomy 21 cells, including lower viability and increased dependency on serine-driven lipid synthesis. Our studies establish a critical role of aneuploidy, independent of triplicated gene identity, in driving cellular defects associated with trisomy 21

Quantitative proteomic analysis reveals posttranslational responses to aneuploidy in yeast

Aneuploidy causes severe developmental defects and is a near universal feature of tumor cells. Despite its profound effects, the cellular processes affected by aneuploidy are not well characterized. Here, we examined the consequences of aneuploidy on the proteome of aneuploid budding yeast strains. We show that although protein levels largely scale with gene copy number, subunits of multi-protein complexes are notable exceptions. Posttranslational mechanisms attenuate their expression when their encoding genes are in excess. Our proteomic analyses further revealed a novel aneuploidy-associated protein expression signature characteristic of altered metabolism and redox homeostasis. Indeed aneuploid cells harbor increased levels of reactive oxygen species (ROS). Interestingly, increased protein turnover attenuates ROS levels and this novel aneuploidy-associated signature and improves the fitness of most aneuploid strains. Our results show that aneuploidy causes alterations in metabolism and redox homeostasis. Cells respond to these alterations through both transcriptional and posttranscriptional mechanisms. DOI: http://dx.doi.org/10.7554/eLife.03023.00

Transducer-Like Protein in Campylobacter jejuni With a Role in Mediating Chemotaxis to Iron and Phosphate

Chemotaxis-mediated motility enables Campylobacter jejuni to navigate through complex environmental gradients and colonize diverse niches. C. jejuni is known to possess several methyl accepting chemotaxis proteins (MCPs), also called transducer-like proteins (Tlps). While the role of some of the Tlps in chemotaxis has been identified, their regulation and role in virulence is still not very clear. Here, we investigated the contribution of Tlp2 to C. jejuni chemotaxis, stress survival and colonization of the chicken gastrointestinal tract. The Δtlp2 deletion mutant showed decreased chemotaxis toward aspartate, pyruvate, inorganic phosphate (Pi), and iron (FeSO4). Transcriptional analysis of tlp2 with a promoter fusion reporter assay revealed that the tlp2 promoter (Ptlp2) was induced by Pi and iron, both in the ferrous (Fe2+) and ferric form (Fe3+). RT-PCR analysis using overlapping primers indicated that the phoX gene, located immediately downstream of tlp2, is co-transcribed with tlp2. A transcription start site was identified at 53 bp upstream of the tlp2 start codon. The Δtlp2 mutant showed decreased colonization of the chicken gastrointestinal tract. Collectively, our findings revealed that the tlp2 plays a role in C. jejuni pathogenesis and colonization in the chicken host and its expression is regulated by iron

Suppressing Aneuploidy-Associated Phenotypes Improves the Fitness of Trisomy 21 Cells

An abnormal number of chromosomes, or aneuploidy, accounts for most spontaneous abortions, causes developmental defects, and is associated with aging and cancer. The molecular mechanisms by which aneuploidy disrupts cellular function remain largely unknown. Here, we show that aneuploidy disrupts the morphology of the nucleus. Mutations that increase the levels of long-chain bases suppress nuclear abnormalities of aneuploid yeast independent of karyotype identity. Quantitative lipidomics indicates that long-chain bases are integral components of the nuclear membrane in yeast. Cells isolated from patients with Down syndrome also show that abnormal nuclear morphologies and increases in long-chain bases not only suppress these abnormalities but also improve their fitness. We obtained similar results with cells isolated from patients with Patau or Edward syndrome, indicating that increases in long-chain bases improve the fitness of aneuploid cells in yeast and humans. Targeting lipid biosynthesis pathways represents an important strategy to suppress nuclear abnormalities in aneuploidy-associated diseases

Diagnostic performance of the 2022 KLCA-NCC criteria for hepatocellular carcinoma on magnetic resonance imaging with extracellular contrast and hepatobiliary agents: comparison with the 2018 KLCA-NCC criteria

Background/Aim This study aimed to determine the diagnostic performance of 2022 Korean Liver Cancer Association-National Cancer Center (KLCA-NCC) imaging criteria compared with the 2018 KLCA-NCC for hepatocellular carcinoma (HCC) in high-risk patients using magnetic resonance imaging (MRI). Methods This retrospective study included 415 treatment-naïve patients (152 patients who underwent extracellular contrast agent [ECA]-MRI and 263 who underwent hepatobiliary agent [HBA]-MRI; 535 lesions, including 412 HCCs) with a high risk of HCC who underwent contrast-enhanced MRI. Two readers evaluated all lesions according to the 2018 and 2022 KLCA-NCC imaging diagnostic criteria, and the per-lesion diagnostic performances were compared. Results In “definite” HCC category of both 2018 and 2022 KLCA-NCC, HBA-MRI showed a significantly higher sensitivity for the diagnosis of HCC than ECA-MRI (77.0% vs. 64.3%, P=0.006) without a significant difference in specificity (94.7% vs. 95.7%, P=0.801). On ECAMRI, “definite” or “probable” HCC categories of the 2022 KLCA-NCC had significantly higher sensitivity than those of the 2018 KLCA-NCC (85.3% vs. 78.3%, P=0.002) with identical specificity (93.6%). On HBA-MRI, the sensitivity and specificity of “definite” or “probable” HCC categories of both 2018 and 2022 KLCA-NCC were not significantly different (83.3% vs. 83.6%, P>0.999 and 92.1% vs. 90.8%, P>0.999, respectively). Conclusions In “definite” HCC category of both 2018 and 2022 KLCA-NCC, HBA-MRI provides better sensitivity than ECA-MRI without compromising specificity. On ECA-MRI, “definite” or “probable” HCC categories of the 2022 KLCA-NCC may improve sensitivity in the diagnosis of HCC compared with the 2018 KLCA-NCC