The host immune regulator factor H interacts via two contact sites with the PspC protein of Streptococcus pneumoniae and mediates adhesion to host epithelial cells

Pneumococcal surface protein C (PspC) of Streptococcus pneumoniae is a key virulence factor that mediates adhesion to host cells and immune evasion of the host complement. PspC binds the host immune and complement regulator factor H, which is composed of 20 short consensus repeats (SCR). This interaction contributes to pneumococcal virulence. In this study, we identified within the factor H protein two separate PspC binding regions, which were localized to SCR8-11 and SCR19-20, by using recombinant factor H deletion constructs for Western blotting assays and surface plasmon resonance studies. A detailed analysis of binding epitopes in these SCR by peptide spot arrays identified several linear binding regions within the sequences of SCR8-11 and SCR19-20. In addition, the factor H binding site was mapped within the pneumococcal PspC protein to a 121-aa-long stretch positioned in the N terminus (residues 38-158). Factor H attached to the surface of pneumococci via PspC significantly enhanced pneumococcal adherence to host epithelial and endothelial cells. This adhesion was specific and was blocked with a truncated N-terminal factor H-binding fragment of PspC. In conclusion, the acquisition of factor H by pneumococci via PspC occurs via two contact sites located in SCR8-11 and SCR19-20, and factor H attached to the surface of the pneumococcus promotes adhesion to both host epithelial and endothelial cells.     

The Miocene Architectonicidae (Gastropoda) of Chile

Three new species of Architectonicidae Heliacinae,Heliacus (Torinista) chonos, Heliacus (Grandeliacus) antu andSolatisonax bieleri, are described. These include the first reports ofGrandeliacus andSolatisonax from Chile.Solarium australe Philippi, 1887 is an earlier name forHeliacus (Torinista) bahamondei Frassinetti & Covacevich, 1981, but is a junior homonym ofS. australe Philippi, 1849. Type material and new specimens of the five previously described architectonicid species from Chile are described and figured for comparison. Together with other gastropod taxa from the same deposits, Architectonicidae provide evidence for tropical to subtropical water temperatures in central Chile during the early Miocene.     

Low-level herbivory by root-knot nematodes (Meloidogyne incognita) modifies root hair morphology and rhizodeposition in host plants (Hordeum vulgare)

Low amounts of root infestation by plant parasitic nematodes are suggested to increase nutrient supply and in turn enhance microbial activity and net mineralization rate in the rhizosphere. These effects are generally related to “leakage” of plant-derived metabolites from damaged roots. Besides leakage, the present study examines other nematode–host interactions such as alterations in root exudation and morphology, which were almost not considered yet. This includes undamaged root parts in order to assess systemic plant response. The root-knot nematode Meloidogyne incognita (Kofoid and White 1919; Chitwood 1949) and barley (Hordeum vulgare L. cv. Europa) was used as model system. Host plants were grown in mini-rhizotrons inoculated with 0, 2,000, 4,000 or 8,000 M. incognita for 4 weeks. Root morphology, rhizodeposition (sugars, carboxylates, amino acids), and rhizosphere microbial communities (PLFAs) were assessed. In treatments with 4,000 nematodes, shoot biomass, total N and P content increased by the end of the experiment. Generally, an enhanced release of plant metabolites (sugars, carboxylates, amino acids) from the apical root zone occurred 1 week after inoculation with 4,000 and 8,000 M. incognita, indicating root leakage. Low levels of root herbivory stimulated root hair elongation in both infected and uninfected roots. These systemic changes in root morphology likely contributed to the increased sugar exudation in uninfected roots in all nematode treatments at 3 weeks after inoculation. Root-knots formed a separate microhabitat within the root-system. They were characterised by decreased rhizodeposition and increased fungal to bacterial ratio in the adhering rhizosphere soil. The present study provides the first evidence that, apart from leakage, nematode root herbivory at background levels induces local and systemic effects on root morphology and exudation, which in turn may affect plant performance.     

Cytosolic proteins contribute to surface plasminogen recruitment of Neisseria meningitidis

Plasminogen recruitment is a common strategy of pathogenic bacteria and results in a broad-spectrum surface-associated protease activity. Neisseria meningitidis has previously been shown to bind plasminogen. In this study, we show by several complementary approaches that endolase, DnaK, and peroxiredoxin, which are usually intracellular proteins, can also be located in the outer membrane and act as plasminogen receptors. Internal binding motifs, rather than C-terminal lysine residues, are responsible for plasminogen binding of the N. meningitidis receptors. Recombinant receptor proteins inhibit plasminogen association with N. meningitidis in a concentration-dependent manner. Besides binding purified plasminogen, N. meningitidis can also acquire plasminogen from human serum. Activation of N. meningitidis-associated plasminogen by urokinase results in functional activity and allows the bacteria to degrade fibrinogen. Furthermore, plasmin bound to N. meningitidis is protected against inactivation by alpha(2)-antiplasmin.     

Engineering the rRNA decoding site of eukaryotic cytosolic ribosomes in bacteria

Structural and genetic studies on prokaryotic ribosomes have provided important insights into fundamental aspects of protein synthesis and translational control and its interaction with ribosomal drugs. Comparable mechanistic studies in eukaryotes are mainly hampered by the absence of both high-resolution crystal structures and efficient genetic models. To study the interaction of aminoglycoside antibiotics with selected eukaryotic ribosomes, we replaced the bacterial drug binding site in 16S rRNA with its eukaryotic counterpart, resulting in bacterial hybrid ribosomes with a fully functional eukaryotic rRNA decoding site. Cell-free translation assays demonstrated that hybrid ribosomes carrying the rRNA decoding site of higher eukaryotes show pronounced resistance to aminoglycoside antibiotics, equivalent to that of rabbit reticulocyte ribosomes, while the decoding sites of parasitic protozoa show distinctive drug susceptibility. Our findings suggest that phylogenetically variable components of the ribosome, other than the rRNA-binding site, do not affect aminoglycoside susceptibility of the protein-synthesis machinery. The activities of the hybrid ribosomes indicate that helix 44 of the rRNA decoding site behaves as an autonomous domain, which can be exchanged between ribosomes of different phylogenetic domains for study of function.     

Tumor growth fraction, expression of estrogen and progesterone receptors, p53, bcl-2 and cathepsin D activity in primary ductal invasive breast carcinoma and their axillary lymph node metastases

The aim of this paper is to determine similarities and differences between tumor cell subclones in cases of ductal invasive breast carcinoma, and which occupy primary tumor and local axillary lymph metastases. The tumor growth fraction evaluated by Ki-67 was analyzed along with the expression level of estrogen and progesterone receptors, protein p53, proto-oncogene protein bcl-2 and cathepsin D in 60 patients. Metastatic lymph node in axilla has a higher growth fraction of the tumor cells than the primary tumor (p = 0.045), as well as the higher level of bcl-2 overexpression (p = 0.014). No statistically significant difference was found in the presence of immunohistochemically identified estrogen receptors (p = 0.161) and progesterone receptors (p = 0.081) between the primary tumor and the metastatic lymph node in axilla. Likewise, no difference was found between the immunohistochemical evaluation of p53 (p = 0.356) and cathepsin D activity (p = 0.928). A higher growth fraction of the tumor cells and the higher level of bcl-2 overexpression in metastatic tumor cells indicate the more aggressive cell subclones. This study does not support the routine testing of both primary tumor and locoregional metastasis to evaluate the breast cancer hormone receptor status.     

Spatial distribution of sponge-associated bacteria in the Mediterranean sponge Tethya aurantium

The local distribution of the bacterial community associated with the marine sponge Tethya aurantium Pallas 1766 was studied. Distinct bacterial communities were found to inhabit the endosome and cortex. Clear differences in the associated bacterial populations were demonstrated by denaturing gradient gel electrophoresis (DGGE) and analysis of 16S rRNA gene clone libraries. Specifically associated phylotypes were identified for both regions: a new phylotype of Flexibacteria was recovered only from the sponge cortex, while Synechococcus species were present mainly in the sponge endosome. Light conduction via radiate spicule bundles conceivably facilitates the unusual association of Cyanobacteria with the sponge endosome. Furthermore, a new monophyletic cluster of sponge-derived 16S rRNA gene sequences related to the Betaproteobacteria was identified using analysis of 16S rRNA gene clone libraries. Members of this cluster were specifically associated with both cortex and endosome of T. aurantium.     

The C-terminus of CIS defines its interaction pattern

Proteins of the SOCS (suppressors of cytokine signalling) family are characterized by a conserved modular structure with pre-SH2 (Src homology 2), SH2 and SOCS-box domains. Several members, including CIS (cytokine-inducible SH2 protein), SOCS1 and SOCS3, are induced rapidly upon cytokine receptor activation and function in a negative-feedback loop, attenuating signalling at the receptor level. We used a recently developed mammalian two-hybrid system [MAPPIT (mammalian protein-protein interaction trap)] to analyse SOCS protein-interaction patterns in intact cells, allowing direct comparison with biological function. We find that, besides the SH2 domain, the C-terminal part of the CIS SOCS-box is required for functional interaction with the cytokine receptor motifs examined, but not with the N-terminal death domain of the TLR (Toll-like receptor) adaptor MyD88. Mutagenesis revealed that one single tyrosine residue at position 253 is a critical binding determinant. In contrast, substrate binding by the highly related SOCS2 protein, and also by SOCS1 and SOCS3, does not require their SOCS-box.     

On-line monitoring of infected Sf-9 insect cell cultures by scanning permittivity measurements and comparison with off-line biovolume measurements

Two infected Sf-9 cell cultures were monitored on-line by multi-frequency permittivity measurements using the Fogale BIOMASS SYSTEM^® and by applying different off-line methods (CASY^®1, Vi-CELL?, packed cell volume) to measure the biovolume and the mean diameter of the cell population. During the growth phase and the early infection phase the measured permittivity at the working frequency correlated well with the different off-line methods for the biovolume. We found a value of 0.67 pF cm^?1 permittivity per unit of total biovolume (CASY) (μL mL^?1). After the maximum value in the permittivity was reached, i.e. when the viability of the cultures decreased significantly, we observed different time courses for the biovolume depending on the applied method. The differences were compared and could be explained by the underlying measurement principles. Furthermore, the characteristic frequency (f_C) was calculated from the on-line scanning permittivity measurements. The f_C may provide an indication of changes in cell diameter and membrane properties especially after infection and could also be an indicator for the onset of the virus production phase. The changes in f_C were qualitatively explained by the underlying equation that is correlating f_C and the properties of the cell population (cell diameter, intracellular conductivity and capacitance per membrane area).