A finite element model of cell deformation during magnetic bead twisting.

Magnetic twisting cytometry probes mechanical properties of an adherent cell by applying a torque to a magnetic bead that is tightly bound to the cell surface. Here we have used a three-dimensional finite element model of cell deformation to compute the relationships between the applied torque and resulting bead rotation and lateral bead translation. From the analysis, we computed two coefficients that allow the cell elastic modulus to be estimated from measurements of either bead rotation or lateral bead translation, respectively, if the degree of bead embedding and the cell height are known. Although computed strains in proximity of the bead can be large, the relationships between applied torque and bead rotation or translation remain virtually linear up to bead rotations of 15 degrees, above which geometrical nonlinearities become significant. This appreciable linear range stands in contrast to the intrinsically nonlinear force-displacement relationship that is observed when cells are indented during atomic force microscopy. Finally, these computations support the idea that adhesive forces are sufficient to keep the bead firmly attached to the cell surface throughout the range of working torques.     

Non-native and translocated fish species in Serbia and their impact on the native ichthyofauna

A total of 22 fish species have been introduced into the inland waters of Serbia, either intentionally or accidentally. This paper provides a summary of data concerning time and reason of introduction, mode of expansion, degree of acclimatization, impact on native fish and estimated area of recent distribution. Four of the non-native fish species currently occupy more than 51% of Serbian territory while 5 of them occupy between 21–50% of territory. This paper reviews impacts of introduced freshwater fish in Serbia based on collected data.     

Global diversity of dipteran families (Insecta Diptera) in freshwater (excluding Simulidae, Culicidae, Chironomidae, Tipulidae and Tabanidae)

Today’s knowledge of worldwide species diversity of 19 families of aquatic Diptera in Continental Waters is presented. Nevertheless, we have to face for certain in most groups a restricted knowledge about distribution, ecology and systematic, particularly in the tropical environments. At the same time we realize a dramatically decline or even lack of specialists being able, having the time or the opportunity to extend or even secure the present information. The respective families with approximate numbers of aquatic species are: Blephariceridae (308), Deuterophlebiidae (14), Nyphomyiidae (7), Psychodidae (∼2.000), Scatopsidae (∼5), Tanyderidae (41), Ptychopteridae (69), Dixidae (173), Corethrellidae (97), Chaoboridae (∼50), Thaumaleidae (∼170), Ceratopogonidae (∼6.000), Stratiomyidae (∼43), Empididae (∼660), Lonchopteridae (2), Syrphidae (∼1.080), Sciomyzidae (∼190), Ephydridae (∼1.500), Muscidae (∼870). Numbers of aquatic species will surely increase with increased ecological and taxonomical efforts. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Successful Posaconazole Therapy of Disseminated Alternariosis due to <Emphasis Type="Italic">Alternaria infectoria</Emphasis> in a Heart Transplant Recipient

We report a case of phaeohyphomycosis caused by Alternaria infectoria in a 61-year-old heart transplant recipient with multiple skin lesions and pulmonary infiltrates. The infection spread via the haematogenous route from the primary cutaneous lesions into the lungs. The diagnosis was based on the histopathological examination, direct microscopy, skin lesion cultures and detection of Alternaria DNA in the bronchoalveolar lavage fluid using molecular methods. The treatment consisted of a combination of surgical excision and systemic antifungal therapy. Voriconazole was the first agent used but had a weak effect. Posaconazole was subsequently used to achieve a successful response. The isolate was identified as A. infectoria by sequencing of the rDNA ITS region and the partial β-tubulin gene.     

Opening the black box: an open‐source release of Maxent

This software note announces a new open‐source release of the Maxent software for modeling species distributions from occurrence records and environmental data, and describes a new R package for fitting such models. The new release (ver. 3.4.0) will be hosted online by the American Museum of Natural History, along with future versions. It contains small functional changes, most notably use of a complementary log‐log (cloglog) transform to produce an estimate of occurrence probability. The cloglog transform derives from the recently‐published interpretation of Maxent as an inhomogeneous Poisson process (IPP), giving it a stronger theoretical justification than the logistic transform which it replaces by default. In addition, the new R package, maxnet, fits Maxent models using the glmnet package for regularized generalized linear models. We discuss the implications of the IPP formulation in terms of model inputs and outputs, treating occurrence records as points rather than grid cells and interpreting the exponential Maxent model (raw output) as as an estimate of relative abundance. With these two open‐source developments, we invite others to freely use and contribute to the software.     

Effects of Inoculum Additions in the Presence of a Preestablished Arbuscular Mycorrhizal Fungal Community

Communities of arbuscular mycorrhizal fungi (AMF) are crucial for promoting plant productivity in most terrestrial systems, including anthropogenically managed ecosystems. Application of AMF inocula has therefore become a widespread practice. It is, however, pertinent to understand the mechanisms that govern AMF community composition and their performance in order to design successful manipulations. Here we assess whether the composition and plant growth-promotional effects of a synthetic AMF community can be altered by inoculum additions of the isolates forming the community. This was determined by following the effects of three AMF isolates, each inoculated in two propagule densities into a preestablished AMF community. Fungal abundance in roots and plant growth were evaluated in three sequential harvests. We found a transient positive response in AMF abundance to the intraspecific inoculation only in the competitively weakest isolate. The other two isolates responded negatively to intra- and interspecific inoculations, and in some cases plant growth was also reduced. Our results suggest that increasing the AMF density may lead to increased competition among fungi and a trade-off with their ability to promote plant productivity. This is a key ecological aspect to consider when introducing AMF into soils.     

Methoxy-Substituted Hydroxychalcone Reduces Biofilm Production,Adhesion and Surface Motility of Acinetobacter baumannii by Inhibiting ompA Gene Expression

An increasing lack of available therapeutic options against Acinetobacter baumannii urged researchers to seek alternative ways to fight this extremely resistant nosocomial pathogen. Targeting its virulence appears to be a promising strategy, as it offers considerably reduced selection of resistant mutants. In this study, we tested antibiofilm potential of four synthetic chalcone derivatives against A. baumannii. Compound that showed the greatest activity was selected for further evaluation of its antivirulence properties. Real-time PCR was used to evaluate mRNA expression of biofilm-associated virulence factor genes (ompA, bap, abaI) in treated A. baumannii strains. Also, we examined virulence properties related to the expression of these genes, such as fibronectin- and collagen-mediated adhesion, surface motility, and quorum-sensing activity. The results revealed that the expression of all tested genes is downregulated together with the reduction of adhesion and motility. The conclusion is that 2′-hydroxy-2-methoxychalcone exhibits antivirulence activity against A. baumannii by inhibiting the expression of ompA and bap genes, which is reflected in reduced biofilm formation, adhesion, and surface motility.     

Conserved DNA Motifs,Including the CENP-B Box-like,Are Possible Promoters of Satellite DNA Array Rearrangements in Nematodes

Tandemly arrayed non-coding sequences or satellite DNAs (satDNAs) are rapidly evolving segments of eukaryotic genomes, including the centromere, and may raise a genetic barrier that leads to speciation. However, determinants and mechanisms of satDNA sequence dynamics are only partially understood. Sequence analyses of a library of five satDNAs common to the root-knot nematodes Meloidogyne chitwoodi and M. fallax together with a satDNA, which is specific for M. chitwoodi only revealed low sequence identity (32–64%) among them. However, despite sequence differences, two conserved motifs were recovered. One of them turned out to be highly similar to the CENP-B box of human alpha satDNA, identical in 10–12 out of 17 nucleotides. In addition, organization of nematode satDNAs was comparable to that found in alpha satDNA of human and primates, characterized by monomers concurrently arranged in simple and higher-order repeat (HOR) arrays. In contrast to alpha satDNA, phylogenetic clustering of nematode satDNA monomers extracted either from simple or from HOR array indicated frequent shuffling between these two organizational forms. Comparison of homogeneous simple arrays and complex HORs composed of different satDNAs, enabled, for the first time, the identification of conserved motifs as obligatory components of monomer junctions. This observation highlights the role of short motifs in rearrangements, even among highly divergent sequences. Two mechanisms are proposed to be involved in this process, i.e., putative transposition-related cut-and-paste insertions and/or illegitimate recombination. Possibility for involvement of the nematode CENP-B box-like sequence in the transposition-related mechanism and together with previously established similarity of the human CENP-B protein and pogo-like transposases implicate a novel role of the CENP-B box and related sequence motifs in addition to the known function in centromere protein binding.