The narQP genes for a two-component regulatory system from the deep-sea bacterium Shewanella violacea DSS12.

Shewanella violacea DSS12 is facultative piezophile isolated from the deep-sea. The expression of cydDC genes (required for d-type cytochrome maturation) of the organism is regulated by hydrostatic pressure. In this study, we analyzed the nucleotide sequence upstream of cydDC in detail and found that there are putative binding sites for the NarL protein which is part of a two-component regulatory system also containing the sensor protein NarX. Furthermore, we identified the narQP genes (homologues of narXL) from S. violacea DSS12 and demonstrated the heterologous expression of narP in Escherichia coli. These results will be helpful in examining pressure regulation of gene expression in S. violacea at the molecular level.     

Streptococcus pneumoniae promotes its own survival via choline-binding protein CbpC-mediated degradation of ATG14

ABSTRACT

Streptococcus pneumoniae

is an opportunistic bacterial pathogen that can promote severe infection by overcoming the epithelial and blood-brain barrier. Pneumococcal cell-surface virulence factors, including cell wall-anchored choline-binding proteins (Cbps) play pivotal roles in promoting invasive disease. We reported previously that intracellular pneumococci were detected by hierarchical macroautophagic/autophagic processes that ultimately lead to bacterial elimination. However, whether intracellular pneumococci can evade autophagy by deploying Cbps remains unclear. In this study, we explore the biological functions of Cbps and reveal their roles in manipulating the autophagic process. Specifically, we found that CbpC-activated autophagy takes place via its interactions with ATG14 (autophagy related 14) and SQSTM1/p62 (sequestosome1). Importantly, CbpC dampens host autophagy by promoting ATG14 degradation via the ATG14-CbpC-SQSTM1/p62 axis. CbpC-induced reductions in ATG14 levels result in impaired ATG14-STX17 complex formation. In pneumococcal-infected cells, ATG14 levels are dramatically reduced in a CbpC-dependent manner that results in suppression of autophagy-mediated degradation and enhanced bacterial survival. Taken together, our results reveal a novel mechanism via which pneumococci can manipulate host autophagy responses, in this case, by employing CbpC as a trap to promote ATG14 depletion. Our findings highlight a novel and sophisticated tactic used by S. pneumoniae that serves to promote intracellular survival.     

Theory of Optical Coupling Effects Among Surfactant Au Nanoparticles Films

In previous reports, Dalfovo et al. showed experimentally that thin films of Au nanoparticles (NP) with organic coating change their optical properties when exposed to several analytes in the vapor phase (Anal Chem 84:4886–4892 2012; J Phys Chem C 119:5098–5106 2015). This optical behavior was associated with changes in the mean distance between nanoparticles, which resulted in a displacement of their plasmon bands towards blue or red in the presence of toluene (Tol) or ethanol (EtOH) vapors, respectively. In the report by Dalfovo et al. (J Phys Chem C 119:5098–5106 2015), in-situ grazing-incidence small-angle X-ray spectroscopy (GISAXS) was performed to determine changes in the inter-NP distance within the film. In the present work, we perform theoretical calculations to interpret the results obtained by Dalfovo et al. (Anal Chem 84:4886–4892 2012; J Phys Chem C 119:5098–5106 2015). For this purpose, we employ two different theoretical approaches, a quasi-static method (QS) and the Korringa-Kohn-Rostoker method (KKR), in order to describe the plasmon resonance shift as a function of the inter-NP distance changes during exposure to Tol and EtOH vapors. Both theoretical approaches describe qualitatively the behavior observed in previous experimental results that correlate the plasmon resonant wavelength with the inter-NP distance obtained by GISAXS. Our theoretical results show that the plasmon resonant wavelength strongly depends on the ratio between the inter-particle distance and the diameter of the nanoparticles and consequently, these films could be used for optical tuning.

     

Flower morphology evolution in Jaborosa (Solanaceae): shape and size variation associated with contrasting pollination modes

• Flower morphology is considered an important factor in species diversification because it may influence the efficiency of pollination in different ways (e.g. attraction and mechanical fit with different groups of pollinators). In the present study, we quantified the variation in flower morphology (i.e. shape and size) of the diverse South American genus Jaborosa Juss. (Solanaceae) in relation to contrasting pollination modes: rewarding pollination either by moths or by generalist small insects versus brood-site deceptive pollination by saprophilous flies.
• We examined variations of flower morphology in frontal (pollinator attraction) and sagittal (functional fit with pollinators) views in 12 Jaborosa species using geometric morphometric methods and comparative approaches to infer whether flower shape evolution, not attributable to flower allometry or phylogenetic relationship, is associated with shifts in pollination modes.
• We found remarkable variation in flower morphology among both Jaborosa species and pollination modes, largely in sagittal view. Evolutionary trends in shape of fly-pollinated flowers were mainly attributable to changes in developmental trajectories. Variation in flower architecture facilitated differential pollen placement – on the proboscis of moths, and either on the back or ventral region of saprophilous flies – promoting diversification of the genus.
• Diversification of shape, independent of size, in most of the studied Jaborosa species would indicate adaptation to contrasting pollination modes.