A study on prophagic and chromosomal sodC genes involvement in Escherichia coli O157:H7 biofilm formation and biofilm resistance to H2O2

Introduction. Escherichia coli O157:H7 possesses one chromosomal and two prophagicsodC genes encoding for Cu,Zn superoxide dismutases. We evaluated the contribution ofsodC genes in biofilm formation and its resistance to hydrogen peroxide.Methods. The biofilm of sodC deletion mutants has been studied, in presence or absenceof hydrogen peroxide, by crystal violet in 96-well plates and Scanning Electron Microscopyon glass coverslips.Results. Deletion of prophagic sodC genes had no effect on biofilm construction, in contrastto the chromosomal gene deletion. Hydrogen peroxide treatment showed highercell mortality and morphological alterations in sodC deletion mutants respect to wildtype. These effects were related to the biofilm development stage.Conclusion. The role of the three SodCs is not redundant in biofilm formation and theresistance to oxidative damage. The stage of biofilm development is a crucial factor foran effective sanitization

Role of ZnuABC and ZinT in Escherichia coli O157:H7 zinc acquisition and interaction with epithelial cells

BACKGROUND: Zinc is an essential element for all living cells. Recent studies have shown that the ZnuABC zinc uptake system significantly contributes to the ability of several pathogens to multiply in the infected host and cause disease, suggesting that zinc is scarcely available within different tissues of the host. To better understand the role of zinc in bacterial pathogenicity, we have undertaken a functional characterization of the role of the ZnuABC-mediated zinc uptake pathway in enterohemorrhagic Escherichia coli O157:H7. RESULTS: In this work we have analyzed the expression and the role in metal uptake of ZnuA, the periplasmic component of the ZnuABC transporter, and of ZinT, another periplasmic protein which has been shown to contribute to zinc recruitment. We report that the expression of zinT and znuA, regulated by Zur, is induced in zinc-poor media, and that inactivation of either of the genes significantly decreases E. coli O157:H7 ability to grow in zinc depleted media. We also demonstrate that ZinT and ZnuA have not a redundant function in zinc homeostasis, as the role of ZinT is subordinated to the presence of ZnuA. Moreover, we have found that znuA and zinT are strongly induced in bacteria adhering to cultured epithelial cells and that lack of ZnuA affects the adhesion ability. In addition we have found that a fraction of apo-ZinT can be secreted outside the cell where the protein might sequester environmental zinc, inducing a condition of metal starvation in surrounding cells. CONCLUSIONS: The here reported results demonstrate that ZnuABC plays a critical role in zinc uptake also in E. coli O157:H7 and that ZinT contributes to the ZnuA-mediated recruitment of zinc in the periplasmic space. Full functionality of the zinc import apparatus is required to facilitate bacterial adhesion to epithelial cells, indicating that the microbial ability to compete with the host cells for zinc binding is critical to establish successful infections. The observation that ZinT can be secreted when it is in the apo-form suggests that its presence in the extracellular environment may somehow contribute to metal uptake or facilitate bacterial colonization of the intestinal epithelia

Regulatory and structural properties differentiating the chromosomal and the bacteriophage-associated Escherichia coli O157:H7 Cu, Zn Superoxide Dismutases

<p>Abstract</p> <p>Background</p> <p>Highly virulent enterohemorrhagic <it>Escherichia coli </it>O157:H7 strains possess three <it>sodC </it>genes encoding for periplasmic Cu, Zn superoxide dismutases: <it>sodC</it>, which is identical to the gene present in non-pathogenic <it>E. coli </it>strains, and <it>sodC</it>-F1 and <it>sodC</it>-F2, two nearly identical genes located within lambdoid prophage sequences. The significance of this apparent <it>sodC </it>redundancy in <it>E. coli </it>O157:H7 has not yet been investigated.</p> <p>Results</p> <p>We report that strains deleted of one or more <it>sodC </it>genes are less resistant than the wild type strain to a challenge with hydrogen peroxide, thus confirming their involvement in the bacterial antioxidant apparatus. To understand if the different <it>sodC </it>genes have truly overlapping functions, we have carried out a comparison of the functional, structural and regulatory properties of the various <it>E. coli </it>O157:H7 SodC enzymes. We have found that the chromosomal and prophagic <it>sodC </it>genes are differentially regulated <it>in vitro</it>. <it>sodC </it>is exclusively expressed in aerobic cultures grown to the stationary phase. In contrast, <it>sodC</it>-F1 and <it>sodC</it>-F2 are expressed also in the logarithmic phase and in anaerobic cultures. Moreover, the abundance of SodC-F1/SodC-F2 increases with respect to that of SodC in bacteria recovered from infected Caco-2 cells, suggesting higher expression/stability of SodC-F1/SodC-F2 in intracellular environments. This observation correlates with the properties of the proteins. In fact, monomeric SodC and dimeric SodC-F1/SodC-F2 are characterized by sharp differences in catalytic activity, metal affinity, protease resistance and stability.</p> <p>Conclusion</p> <p>Our data show that the chromosomal and bacteriophage-associated <it>E. coli </it>O157:H7 <it>sodC </it>genes have different regulatory properties and encode for proteins with distinct structural/functional features, suggesting that they likely play distinctive roles in bacterial protection from reactive oxygen species. In particular, dimeric SodC-F1 and SodC-F2 possess physico-chemical properties which make these enzymes more suitable than SodC to resist the harsh environmental conditions which are encountered by bacteria within the infected host.</p

Hemorheological profiles and chronic inflammation markers in transfusion-dependent and non-transfusion- dependent thalassemia

: The rheological properties of blood play an important role in regulating blood flow in micro and macro circulation. In thalassemia syndromes red blood cells exhibit altered hemodynamic properties that facilitate microcirculatory diseases: increased aggregation and reduced deformability, as well as a marked increase in adherence to the vascular endothelial cells. A personalized approach to treating thalassemia patients (transfusions, iron chelation, and splenectomy), has increased patients' life expectancy, however they generally present many complications and several studies have demonstrated the presence of high incidence of thromboembolic events. In this study the hemorheological profiles of thalassemia patients have been characterized to point out new indices of vascular impairment in thalassemia. Plasma viscosity, blood viscosities at low and high shear rates (η1 and η200, respectively), erythrocyte aggregation index (η1/η200), and the erythrocyte viscoelastic profile (elastic modulus G', and viscous modulus G") have been studied in transfusion-dependent and non-transfusion-dependent thalassemia patients. Moreover, the levels of inflammation biomarkers in thalassemia have been evaluated to investigate a relationship between the biomarkers, the disease severity and the rheological parameters. The biomarkers studied are the main components of the immune and endothelial systems or are related to vascular inflammation: cytokines (IL-2, IL-6, IL-10, IL-17A, TNF-alpha), chemokines (IL-8, MIP-1alpha), adipocytokines (leptin and adiponectin), growth factors (VEGF, angiopoietin-1), adhesion molecules (ICAM-1, VCAM-1, E-selectin, L-selectin), and a monocyte/macrophage activation marker (CD163). This study shows that transfusion-dependent thalassemia patients, both major and intermedia, have blood viscosities comparable to those of healthy subjects. Non-transfusion-dependent thalassemia intermedia patients show high blood viscosities at low shear rates (η1), corresponding to the flow conditions of the microcirculation, an increase in erythrocyte aggregation, and high values of the elastic G' and viscous G" modules that reflect a reduced erythrocyte deformability and an increase in blood viscosity. Levels of cytokines, chemokines and adhesion molecules are different in transfusion- and non-transfusion dependent patients and positive correlations between η1 or η1/η200 and the cytokines IL-6 and IL-10 have been observed. The evaluation of the hemorheological profiles in thalassemia can provide new indicators of vascular impairment and disease severity in thalassemia in order to prevent the onset of thromboembolic events

A different Venice

The Northern Lagoon is part of the world-famous Venetian Lagoon in the Italian region of Veneto, but, in contrast to the well-known and exploited Central Lagoon, has managed to preserve its original landscape to a high degree. The future of this tranquil landscape, however, is anything but certain. Its further existence calls for landscape design interventions that consider the balance of three dialectical pairs: land & water, human & non-human and nature & artifice. A related comprehensive design strategy has to focus on the entire lagoon as one system where many environmental, morphological, and social singularities coexist

A different Venice

The Northern Lagoon is part of the world-famous Venetian Lagoon in the Italian region of Veneto, but, in contrast to the well-known and exploited Central Lagoon, has managed to preserve its original landscape to a high degree. The future of this tranquil landscape, however, is anything but certain. Its further existence calls for landscape design interventions that consider the balance of three dialectical pairs: land &amp; water, human &amp; non-human and nature &amp; artifice. A related comprehensive design strategy has to focus on the entire lagoon as one system where many environmental, morphological, an

A different Venice

The Northern Lagoon is part of the world-famous Venetian Lagoon in the Italian region of Veneto, but, in contrast to the well-known and exploited Central Lagoon, has managed to preserve its original landscape to a high degree. The future of this tranquil landscape, however, is anything but certain. Its further existence calls for landscape design interventions that consider the balance of three dialectical pairs: land & water, human & non-human and nature & artifice. A related comprehensive design strategy has to focus on the entire lagoon as one system where many environmental, morphological, and social singularities coexist