Gene flow in environmental Legionella pneumophila leads to genetic and pathogenic heterogeneity within a Legionnaires’ disease outbreak

Background

Legionnaires’ disease is a severe form of pneumonia caused by the environmental bacterium Legionella pneumophila. Outbreaks commonly affect people with known risk factors, but the genetic and pathogenic complexity of L. pneumophila within an outbreak is not well understood. Here, we investigate the etiology of the major Legionnaires’ disease outbreak that occurred in Edinburgh, UK, in 2012, by examining the evolutionary history, genome content, and virulence of L. pneumophila clinical isolates.

Results

Our high resolution genomic approach reveals that the outbreak was caused by multiple genetic subtypes of L. pneumophila, the majority of which had diversified from a single progenitor through mutation, recombination, and horizontal gene transfer within an environmental reservoir prior to release. In addition, we discover that some patients were infected with multiple L. pneumophila subtypes, a finding which can affect the certainty of source attribution. Importantly, variation in the complement of type IV secretion systems encoded by different genetic subtypes correlates with virulence in a Galleria mellonella model of infection, revealing variation in pathogenic potential among the outbreak source population of L. pneumophila.

Conclusions

Taken together, our study indicates previously cryptic levels of pathogen heterogeneity within a Legionnaires’ disease outbreak, a discovery that impacts on source attribution for future outbreak investigations. Furthermore, our data suggest that in addition to host immune status, pathogen diversity may be an important influence on the clinical outcome of individual outbreak infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0504-1) contains supplementary material, which is available to authorized users.     

Lack of Matrilin-2 Favors Liver Tumor Development via Erk1/2 and GSK-3β Pathways In Vivo

Matrilin-2 (Matn2) is a multidomain adaptor protein which plays a role in the assembly of extracellular matrix (ECM). It is produced by oval cells during stem cell-driven liver regeneration. In our study, the impact of Matn2 on hepatocarcinogenesis was investigated in Matn2^-/- mice comparing them with wild-type (WT) mice in a diethylnitrosamine (DEN) model. The liver tissue was analyzed macroscopically, histologically and immunohistochemically, at protein level by Proteome Profiler Arrays and Western blot analysis. Matn2^-/- mice exhibited higher susceptibility to hepatocarcinogenesis compared to wild-type mice. In the liver of Matn2^-/- mice, spontaneous microscopic tumor foci were detected without DEN treatment. After 15 μg/g body weight DEN treatment, the liver of Matn2^-/- mice contained macroscopic tumors of both larger number and size than the WT liver. In contrast with the WT liver, spontaneous phosphorylation of EGFR, Erk1/2 GSK-3α/β and retinoblastoma protein (p-Rb), decrease in p21/CIP1 level, and increase in β-Catenin protein expression were detected in Matn2^-/- livers. Focal Ki-67 positivity of these samples provided additional support to our presumption that the lack of Matn2 drives the liver into a pro-proliferatory state, making it prone to tumor development. This enhanced proliferative capacity was further increased in the tumor nodules of DEN-treated Matn2^-/- livers. Our study suggests that Matn2 functions as a tumor suppressor in hepatocarcinogenesis, and in this process activation of EGFR together with that of Erk1/2, as well as inactivation of GSK-3β, play strategic roles.     

Righting and turning in mid-air using appendage inertia: reptile tails, analytical models and bio-inspired robots

Unlike the falling cat, lizards can right themselves in mid-air by a swing of their large tails in one direction causing the body to rotate in the other. Here, we developed a new three-dimensional analytical model to investigate the effectiveness of tails as inertial appendages that change body orientation. We anchored our model using the morphological parameters of the flat-tailed house gecko Hemidactylus platyurus. The degree of roll in air righting and the amount of yaw in mid-air turning directly measured in house geckos matched the model's results. Our model predicted an increase in body roll and turning as tails increase in length relative to the body. Tails that swung from a near orthogonal plane relative to the body (i.e. 0-30° from vertical) were the most effective at generating body roll, whereas tails operating at steeper angles (i.e. 45-60°) produced only half the rotation. To further test our analytical model's predictions, we built a bio-inspired robot prototype. The robot reinforced how effective attitude control can be attained with simple movements of an inertial appendage.     

Tumor cell and carcinoma-associated fibroblast interaction regulates matrix metalloproteinases and their inhibitors in oral squamous cell carcinoma

Co-culture of periodontal ligament (PDL) fibroblasts and SCC-25 oral squamous carcinoma cells (OSCC), results in conversion of PDLs into carcinoma-associated fibroblasts (CAFs). Paracrin circuits between CAFs and OSCC cells were hypothesized to regulate the gene expression of matrix remodeling enzymes in their co-culture, which was performed for 7days, followed by analysis of the mRNA/protein expression and activity of metalloproteinases (MMPs), their tissue inhibitors (TIMPs) and other relevant genes. Interleukin1-β, transforming growth factor-β1, fibronectin and αvβ6 integrin have shown to be involved in the regulation of the MMP and TIMP gene expression in co-culture of CAFs and tumor cells. In addition, these cells also cooperated in activation of MMP pro-enzymes. It is particularly interesting that the fibroblast-produced inactive MMP-2 has been activated by the tumor-cell-produced membrane-type 1 matrix metalloproteinase (MT1-MMP). The crosstalk between cancer- and the surrounding fibroblast stromal-cells is essential for the fine tuning of cancer cells invasivity.     

An integrative study of insect adhesion: mechanics and wet adhesion of pretarsal pads in ants

Many animals that locomote by legs possess adhesive pads. Suchorgans are rapidly releasable and adhesive forces can be controlledduring walking and running. This capacity results from the interactionof adhesive with complex mechanical systems. Here we presentan integrative study of the mechanics and adhesion of smoothattachment pads (arolia) in Asian Weaver ants (Oecophylla smaragdina).Arolia can be unfolded and folded back with each step. Theyare extended either actively by contraction of the claw flexormuscle or passively when legs are pulled toward the body. Regulationof arolium use and surface attachment includes purely mechanicalcontrol inherent in the arrangement of the claw flexor system. Predictions derived from a ‘wet’ adhesion mechanismwere tested by measuring attachment forces on a smooth surfaceusing a centrifuge technique. Consistent with the behavior ofa viscid secretion, frictional forces per unit contact arealinearly increased with sliding velocity and the increment stronglydecreased with temperature. We studied the nature and dimensions of the adhesive liquidfilm using Interference Reflection Microscopy (IRM). Analysisof ‘footprint’ droplets showed that they are hydrophobicand form low contact angles. In vivo IRM of insect pads in contactwith glass, however, revealed that the adhesive liquid filmnot only consists of a hydrophobic fluid, but also of a volatile,hydrophilic phase. IRM allows estimation of the height of theliquid film and its viscosity. Preliminary data indicate thatthe adhesive secretion alone is insufficient to explain theobserved friction and that rubbery deformation of the pad cuticleis involved.     

An inexpensive tag for short-term studies in milkfish (Cbanos chanos Forsskal) and in seabass (Lates calcarifer Bloch)

An opercular tag for marking adult milkfish ( Chanos chanos Forsskal) and seabass ( Lates calcarifer Bloch) is described. High tag retention and relatively low mortality rates were observed in adult fish handled two to ten times during 14-to 60-day tests. The features and advantages of the tag for marking large-sized fish in short-term studies are discussed.

Zusammenfassung

Eine preiswerte Markierung für Kurzzeitstudien des Milchfisches (Chanos chanos Forsskal) und der Centropomidae (Lates calcarifer Bloch)
Eine Kiemendeckel-Markierung für adulte Milchfische (Chanos chanos Forsskal) und Centropomidae (Lates calcacifer Bloch) wird beschrieben. Sie zeichnet sich durch gute Haltbarkeit aus und verursacht relativ geringe Mortalität bei adulten Fischen, die in Versuchen von 14 bis 60 Tage Dauer 2-bis 10mal untersucht wurden. Die Eigenschaften und Vorteile dieser Markierung für große Fische in Kurzzeitstudien werden diskutiert.

Résumé

Un marquage économique pour des études de courte durée du chanidé (Chanos chanos Forsskal) et du centropomidé (Lates calcarifer Bloch)
Un marquage d'opercule pour les chanidés (Chanos chanos Forsskal) et les centropomidés (Lates calcarifer Bloch) adultes est décrit. Une bonne conservation et une mortalité relativement basse ont été observées chez des poissons adultes examinés 2 à 10 fois pendant des expériences d'une durée de 14 à 60 jours. Les caractéristiques et les avantages du marquage de poissons de grande taille pendant des expériences d'une courte durée sont discutés.     

Patterns of extensive genetic differentiation and variation among European harbor seals (Phoca vitulina vitulina) revealed using microsatellite DNA polymorphisms

The harbor seal (Phoca vitulina) has the most extensive distribution of any phocid seal species. An analysis of population structure in this species across its European range was made using 7 phocid derived microsatellites in a sample of 1,029 individuals from 12 separate geographic areas. Despite the species potential for long-distance movement, significant genetic differentiation between areas was observed using an unbiased estimator of RST. Six distinct population units were identified: Ireland-Scotland, English east coast, Waddensea, western Scandinavia (Norway-Kattegat-Skagerrak-west Baltic), east Baltic, and Iceland. Little local substructuring is present along coastlines with a continuous distribution of breeding animals, but differentiation does increase with geographic distance. The degree of differentiation is greater over equivalent distances where the distribution is discontinuous, such as along coasts where breeding colonies are separated by large distances or by stretches of open sea. Patterns of population differentiation derived from microsatellites are very similar to those obtained from previous mitochondrial DNA analysis and suggest that philopatry in harbor seals operates over 300-500 km. In Europe, harbor seals have experienced a complex demographic history and patterns of population structure are likely to have been affected by natural environmental influences such as Pleistocene glaciations and epizootics. Comparison of Nm values from an unbiased estimator of RST, GST, and theta are consistent and, in some cases, may indicate populations where conditions deviate from the expectations of the RST model.