Highly Invasive Listeria monocytogenes Strains Have Growth and Invasion Advantages in Strain Competition

Multiple Listeria monocytogenes strains can be present in the same food sample; moreover, infection with more than one L. monocytogenes strain can also occur. In this study we investigated the impact of strain competition on the growth and in vitro virulence potential of L. monocytogenes. We identified two strong competitor strains, whose growth was not (or only slightly) influenced by the presence of other strains and two weak competitor strains, which were outcompeted by other strains. Cell contact was essential for growth inhibition. In vitro virulence assays using human intestinal epithelial Caco2 cells showed a correlation between the invasion efficiency and growth inhibition: the strong growth competitor strains showed high invasiveness. Moreover, invasion efficiency of the highly invasive strain was further increased in certain combinations by the presence of a low invasive strain. In all tested combinations, the less invasive strain was outcompeted by the higher invasive strain. Studying the effect of cell contact on in vitro virulence competition revealed a complex pattern in which the observed effects depended only partially on cell-contact suggesting that competition occurs at two different levels: i) during co-cultivation prior to infection, which might influence the expression of virulence factors, and ii) during infection, when bacterial cells compete for the host cell. In conclusion, we show that growth of L. monocytogenes can be inhibited by strains of the same species leading potentially to biased recovery during enrichment procedures. Furthermore, the presence of more than one L. monocytogenes strain in food can lead to increased infection rates due to synergistic effects on the virulence potential.     

A phylogenomic resolution for the taxonomy of Aegean green lizards

Lacerta pamphylica and Lacerta trilineata are two currently recognized green lizard species with a historically problematic taxonomy. In cases of tangled phylogenies, next-generation sequencing and double-digest restriction-site-associated DNA protocols can provide a wealth of genomic data and resolve difficult taxonomic issues. Here, we generated genome-wide SNPs and mitochondrial sequences, and applied molecular species delimitation approaches to provide a stable taxonomy for the Aegean green lizards. Mitochondrial gene trees, genetic cluster delimitation and population structure analyses converged into recognizing the populations of (a) L. pamphylica, (b) east Aegean islands, Anatolia and Thrace (diplochondrodes lineage), (c) central Aegean islands (citrovittata), and (d) remaining Balkan populations and islands (trilineata), as separate clusters. Phylogenomic analyses revealed a split into two major clades, east and west of the Aegean Barrier, unambiguously showing a sister–clade relationship between pamphylica and diplochondrodes, rendering L. trilineata paraphyletic. Species delimitation models were tested in a Bayesian framework using the genomic SNPs: lumping all populations into a single ‘species’ had the lowest likelihood but the current taxonomy was also outperformed by all other models. All lines of evidence support the Pamphylian green lizard as a valid species; thus, east Aegean L. trilineata should also be considered a distinct species under the name Lacerta diplochondrodes. Finally, evidence from the mitochondrial and nuclear genomes is overwhelmingly in favour of recognizing the morphologically distinct Cycladian green lizards as a distinct species. We propose their elevation to full species under the name Lacerta citrovittata. All remaining insular and continental populations of the Balkan Peninsula represent the species L. trilineata.     

Mammary analogue secretory carcinoma of salivary gland diagnosed on submandibular gland cytology: A case report and review of the literature

Mammary analogue secretory carcinoma of the salivary glands has morphological shares molecular similarities to secretory carcinoma of the breast. Here, we report a 46‐year‐old woman who presented with a right submandibular gland mass. Fine needle aspiration differential diagnosis included oncocytosis, oncocytoma, acinic cell carcinoma and mammary analogue secretory carcinoma. We also review the current literature regarding clinical presentation and diagnostic workup of this entity.     

Diurnal and seasonal trends of water relations in five co-occurring chasmophytic species

The present study examines the seasonal and diurnal patterns of water management by plant species inhabiting the wall fissures of the ancient castle of Patras. Their water status (water potential), stomatal behaviour (leaf resistance and transpiration rate) as well as tissue water relations (turgor loss point, osmoregulation capability and cell wall elasticity) were recorded in relation to season, daytime and respective environmental conditions. Despite some minor deviations, all five species exhibited a water spending strategy with high diurnal transpiration rates through seasons, limited only by the generally low light intensities prevailing at the northwest-facing vertical walls. Progressive shortage of water during summer resulted in the reduction of transpiration in four species. Diurnal water losses caused a reduction of water potential until midday or dusk, which further decreased with the progress of the dry period. However, predawn water potential remained high through all seasons. The above finding, together with the high transpiration, was unexpected for species growing in a very hostile environment as far as water supply is regarded. It could be partly explained by the recently found ability of all five species to absorb dew from leaf surfaces. However, such plants should also possess mechanisms to take up water efficiently from a rather dry substrate. Indeed, pressure–volume analysis revealed substantial seasonal changes in osmoregulatory capacity and minor changes in cell wall elasticity of leaf tissue. Both changes facilitate (the mechanism differs) water uptake from the wall-fissure substrate during the dry period. Although the relative contribution of the two mechanisms was different, they both allowed plants to maintain turgor and thus growth throughout their growing season.     

Setup and use of a two-laser multiphoton microscope for multichannel intravital fluorescence imaging

Characterizing biological mechanisms dependent upon the interaction of many cell types in vivo requires both multiphoton microscope systems capable of expanding the number and types of fluorophores that can be imaged simultaneously while removing the wavelength and tunability restrictions of existing systems, and enhanced software for extracting critical cellular parameters from voluminous 4D data sets. We present a procedure for constructing a two-laser multiphoton microscope that extends the wavelength range of excitation light, expands the number of simultaneously usable fluorophores and markedly increases signal to noise via 'over-clocking' of detection. We also utilize a custom-written software plug-in that simplifies the quantitative tracking and analysis of 4D intravital image data. We begin by describing the optics, hardware, electronics and software required, and finally the use of the plug-in for analysis. We demonstrate the use of the setup and plug-in by presenting data collected via intravital imaging of a mouse model of breast cancer. The procedure may be completed in ～24 h.     

Molecular determinants of modulation of CaV2.1 channels by visinin-like protein 2

CaV2.1 channels, which conduct P/Q-type Ca2+ currents, initiate synaptic transmission at most synapses in the central nervous system. Ca2+/calmodulin-dependent facilitation and inactivation of these channels contributes to short-term facilitation and depression of synaptic transmission, respectively. Other calcium sensor proteins displace calmodulin (CaM) from its binding site, differentially regulate CaV2.1 channels, and contribute to the diversity of short-term synaptic plasticity. The neuronal calcium sensor protein visinin-like protein 2 (VILIP-2) inhibits inactivation and enhances facilitation of CaV2.1 channels. Here we examine the molecular determinants for differential regulation of CaV2.1 channels by VILIP-2 and CaM by construction and functional analysis of chimeras in which the functional domains of VILIP-2 are substituted in CaM. Our results show that the N-terminal domain, including its myristoylation site, the central α-helix, and the C-terminal lobe containing EF-hands 3 and 4 of VILIP-2 are sufficient to transfer its regulatory properties to CaM. This regulation by VILIP-2 requires binding to the IQ-like domain of CaV2.1 channels. Our results identify the essential molecular determinants of differential regulation of CaV2.1 channels by VILIP-2 and define the molecular code that these proteins use to control short-term synaptic plasticity.