IlsA, A Unique Surface Protein of Bacillus cereus Required for Iron Acquisition from Heme, Hemoglobin and Ferritin

The human opportunistic pathogen Bacillus cereus belongs to the B. cereus group that includes bacteria with a broad host spectrum. The ability of these bacteria to colonize diverse hosts is reliant on the presence of adaptation factors. Previously, an IVET strategy led to the identification of a novel B. cereus protein (IlsA, Iron-regulated leucine rich surface protein), which is specifically expressed in the insect host or under iron restrictive conditions in vitro. Here, we show that IlsA is localized on the surface of B. cereus and hence has the potential to interact with host proteins. We report that B. cereus uses hemoglobin, heme and ferritin, but not transferrin and lactoferrin. In addition, affinity tests revealed that IlsA interacts with both hemoglobin and ferritin. Furthermore, IlsA directly binds heme probably through the NEAT domain. Inactivation of ilsA drastically decreases the ability of B. cereus to grow in the presence of hemoglobin, heme and ferritin, indicating that IlsA is essential for iron acquisition from these iron sources. In addition, the ilsA mutant displays a reduction in growth and virulence in an insect model. Hence, our results indicate that IlsA is a key factor within a new iron acquisition system, playing an important role in the general virulence strategy adapted by B. cereus to colonize susceptible hosts

Conductivity of ultrathin Pb films during growth on Si(111) at low temperatures

The electronic properties of thin metallic films strongly depend on their structure. For the preparation of ultrathin films (0.8 to 12 ML) Pb was grown on a Si (111)-$7\times 7$ structure at temperatures below 25 K. Percolation as measured by DC conductance starts at 0.7 ML. Up to 4 ML the growing film is disordered. During continuation of the growth the film recrystallizes epitaxially and layer-by-layer growth connected with oscillations of conductivity and LEED intensities is observed even at 25 K. The defect structure as determined by SPA-LEED and the quantum size effect allow a quantitative description of the conductivity oscillations. The experiments show, that the electronic properties of ultrathin Pb films are clearly correlated with the structural properties of the film

Switching between one and two dimensions: Conductivity of Pb-induced chain structures on Si(557)

We show in a combined study of four-point conductance measurement and tunneling microscopy that surface state conductance induced by one monolayer of Pb on Si(557) can be quasi one dimensional with conductivity values close to typical three-dimensional metals. At a critical temperature of Tc=78K, associated with an order-disorder phase transition and a tenfold superperiodicity along the Pb chains, the system switches from low to high conductance anisotropy, with a semiconductor-insulator transition in the direction perpendicular to the chain structure, while along the chains conductance with a (1/T+const) temperature dependence was found. © 2005 The American Physical Society

Soft-Sensors for Monitoring B. Thuringiensis Bioproduction

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A molecular 'signature' of primary breast cancer cultures; patterns resembling tumor tissue

<p>Abstract</p> <p>Background</p> <p>To identify the spectrum of malignant attributes maintained outside the host environment, we have compared global gene expression in primary breast tumors and matched short-term epithelial cultures.</p> <p>Results</p> <p>In contrast to immortal cell lines, a characteristic 'limited proliferation' phenotype was observed, which included over expressed genes associated with the <it>TGFβ </it>signal transduction pathway, such as <it>SPARC</it>, <it>LOXL1</it>, <it>RUNX1</it>, and <it>DAPK1</it>. Underlying this profile was the conspicuous absence of <it>hTERT </it>expression and telomerase activity, a significant increase in <it>TβRII</it>, its cognate ligand, and the CDK inhibitor, <it>p21</it>^{<it>CIP1/WAF1</it>}. Concurrently, tumor tissue and primary cultures displayed low transcript levels of proliferation-related genes, such as, <it>TOP2A</it>, <it>ANKT</it>, <it>RAD51</it>, <it>UBE2C</it>, <it>CENPA</it>, <it>RRM2</it>, and <it>PLK</it>.</p> <p>Conclusions</p> <p>Our data demonstrate that commonly used immortal cell lines do not reflect some aspects of tumor biology as closely as primary tumor cell cultures. The gene expression profile of malignant tissue, which is uniquely retained by cells cultured on solid substrates, could facilitate the development and testing of novel molecular targets for breast cancer.</p