Diversity of acaropathogenic fungi in Poland and other European countries

The occurrence, species diversity and some aspects of taxonomical affinity and host selectivity of acaropathogenic fungi associated with phytophagous, saprotrophic and predacious mites in Poland and other European countries were investigated on wild and cultivated plants, in insect feeding sites under the bark and in decayed wood. From among 33 species of fungi affecting mites only five species of Entomophthorales were separated and the most numerous were Neozygites floridana mostly on Tetranychus urticae, N. abacaridis on a few eriophyid species, and Conidiobolus coronatus attacking gamasid mites most frequently of the genus Dendrolaelaps. The most frequent mite pathogens occurring in mite communities on plants and in wood infested by insects were of the genus Hirsutella. Until now 13 of their form-species have been recognized in these habitats, but only H. kirchneri, H. necatrix and H. thompsonii (including its variety synnematosa) can be treated as exclusive oligophagous pathogens of phytophagous mites, though their potential host range seems to embrace only selected eriophyid or tarsonemid mites. Taxonomical differentiation of fungal strains was based on close morphological observations and molecular analysis of ITS region sequences. Two new species of acaropathogenic fungi were described in these studies. Hirsutella danubiensis sp. nov. was found in the tetranychid T. urticae, whereas H. vandergeesti sp. nov. affected phytoseiid mites of the genera Amblyseius, Neoseiulus, Seiulus and Typhlodromus, and the tarsonemid Tarsonemus lacustris.     

Laboratory trials to infect insects and nematodes by some acaropathogenic Hirsutella strains (Mycota: Clavicipitaceous anamorphs)

Laboratory assays have been carried out to artificially infect insect larvae of the birch bark-beetle (Scolytus ratzeburgi Jans.-Coleoptera, Scolytidae) and codling moth Cydia pomonella L. -Lepidoptera, Tortricidae) as well as the potato cyst nematode-Globodera rostochiensis Wollenweber, sugar beet nematode-Heterodera schachtii Schmidt and root-knot nematode-Meloidogyne hapla Chif (Nematoda, Heteroderidae), by the phialoconidia of some fungal species of the genus Hirsutella. From among four species tested on insects only H. nodulosa Petch infected about 20% of S. ratzeburgi larvae, whereas H. kirchneri (Rostrup) Minter, Brady et Hall, H. minnesotensis Chen, Liu et Chen, and H. rostrata Ba?azy et Wi?niewski did not affect insect larvae. Only single eggs of the root-knot nematode were infected by H. minnesotensis in the laboratory trials, whereas its larvae remained unaffected. No infection cases of the potato cyst nematode (G. rostochiensis) and sugar beet nematode eggs were obtained. Comparisons of DNA-ITS-region sequences of the investigated strains with GenBank data showed no differences between H. minnesotensis isolates from the nematodes Heterodera glycines Ichinohe and from tarsonemid mites (authors' isolate). A fragment of ITS 2 with the sequence characteristic only for H. minnesotensis was selected. Two cluster analyses indicated close similarity of this species to H. thompsonii as sister clades, but the latter appeared more heterogenous. Insect and mite pathogenic species H. nodulosa localizes close to specialized aphid pathogen H. aphidis, whereas the phytophagous mite pathogens H. kirchneri and H. gregis form a separate sister clade. Hirsutella rostrata does not show remarkable relations to the establishment of aforementioned groups. Interrelated considerations on the morphology, biology and DNA sequencing of investigated Hirsutella species state their identification more precisely and facilitate the establishment of systematic positions.     

Screening and evaluation of acaropathogenic fungi against the bulb mite Rhizoglyphus robini

Bulb mites (Rhizoglyphus robini) damage the bulbs, corns, and tubers of garlic, shallots, and onions. Bulb mites have recently become a serious problem because of the continuous use of acaricides, which has resulted in resistance among bulb mite populations. Thus, there is a need to find alternative control methods to suppress bulb mite populations. Here, we report the results of screening pathogenic fungi for the control of R. robini. The initial screen was performed using 342 isolates of entomopathogenic fungi from soils from South Korea. As a result, 57 isolates of putative acaropathogenic fungi were selected from cadavers of bulb mites supporting fungal sporulation. However, 11 isolates were finally selected for further study through a re-evaluation of the pathogenicity of the isolates. These isolates were identified as two isolates of Metarhizium pemphigi, two isolates of Metarhizium pingshaense, and seven isolates of Metarhizium anisopliae by a microscopic examination and sequence analysis of the ITS region and EF-1α gene. The virulence, thermotolerance and UV-B tolerance of the 11 isolates were further evaluated and compared. Eight isolates showed more than 80% mortality and three isolates showed 100% mortality at 7 days after treatment. The thermotolerance of conidia showed a large difference depending on the fungal isolate, and five isolates showed a conidial germination rate of approximately 60% or more even after 2 h of heat treatment. On the other hand, the UV-B tolerance was very low in all the isolates, and only one isolate showed more than approximately 80% tolerance to 0.1 J cm⁻², but the other isolates showed a conidial germination rate of less than 30%. Based on all of the above results, three isolates, M. anisopliae 4–3-2, 4–8-1, and 4–31-2, were the most effective isolates in controlling bulb mites and could be considered promising biological control agents against bulb mites.     

A tale of three genomes: the kinetoplastids have arrived

July 2005 marked a milestone in kinetoplastid biology research. A tour de force effort led by the Tri-Trypanosomatidae "Tritryp" genome consortium yielded the publication of three prominent kinetoplastid parasite genome sequences: Trypanosoma brucei, Trypanosoma cruzi and Leishmania major. The individual and combined comparative analyses of these three genome sequences, combined with proteomic analyses, have yielded insights into topics ranging from genome evolution and horizontal gene transfer to potential new therapeutic and vaccine targets.     

Teaching professionalism: a tale of three schools

This article compares professionalism education from the vantage points of three different disciplines: medicine, law, and business. In particular, it asks how each of these professions conceives of "professionalism," and how these different conceptions affect what is taught to graduate students. The object of professionalism education differs among these three disciplines, as do the specific challenges to professionalism and professionalism education. The article offers examples of how professionalism is taught in medicine, law, and business, and what each profession might learn from the others in developing their professionalism education and pedagogy.     

A tale of three GTPases and a RIN in endothelial cell adhesion

Endothelial cell adhesion to the extracellular matrix regulates migration and outgrowth of blood vessels during angiogenesis. Cell adhesion is mediated by integrins, which transduce signals from the extracellular environment into the cell and, in turn, are regulated by intracellular signaling molecules. In a paper recently published in Cell Research, Sandri et al. show that RIN2 connects three GTPases, R-Ras, Rab5 and Rac1, to promote endothelial cell adhesion through the regulation of integrin internalization and Rac1 activation.The formation of the vascular tree during development requires the orderly growth of blood vessels to irrigate all organs and tissues. This process of blood vessel remodeling, termed angiogenesis, requires endothelial cell proliferation, adhesion, migration and tube formation¹. Pathological angiogenesis takes place during tumor growth as hypoxia within the tumor induces the release of pro-angiogenic mediators such as vascular endothelial growth factor (VEGF).Small GTPases are critical for the regulation of cell behavior and thus also play a central role in angiogenesis. Small GTPases are 20-25 kDa signaling proteins that cycle between an active GTP-bound and an inactive GDP-bound state. When active, GTPases associate with and activate diverse effector molecules that subsequently relay the signal to other molecules, ultimately leading to a specific cell response. Two classes of proteins facilitate GTPase cycling. Guanine exchange factors (GEFs) catalyze GDP unloading thereby promoting GTP binding and GTPase activation. Conversely, GTPase activating proteins (GAPs) enhance the intrinsic GTP hydrolysis activity of the GTPase leading to its inactivation. Small GTPases form a large superfamily with over 100 members in mammals. Based on structural and functional criteria, the GTPase superfamily is subdivided in Ras, Rab, Rho, Arf and Ran subfamilies, each of them generally, but not exclusively, specialized in the regulation of specific cellular events. For example, Rho GTPases primarily regulate cytoskeletal dynamics; Rab GTPases regulate intracellular membrane trafficking; and Ras GTPases function in the regulation of cell proliferation and survival. However, complex processes such as angiogenesis require the coordinated action of several GTPases. This is evidenced by the work of Sandri et al.² recently published in Cell Research. In their paper, Sandri et al. propose a mechanism for the regulation of endothelial cell adhesion and migration involving three GTPases belonging to different GTPase branches, R-Ras, Rab5 and Rac1. The protein RIN2 (Ras and Rab adaptor 2) brings together R-Ras and Rab5 to form a signaling module that orchestrates integrin trafficking and Rac1 activation, processes that are essential for cell adhesion and migration.Integrins are heterodimeric transmembrane extracellular matrix (ECM) receptors composed of one α and one β chain. In a process known as ''outside-in'' signaling, integrins transmit signals from the extracellular environment to intracellular adaptor and signaling molecules that regulate cell migration, survival and growth. Conversely, during ''inside-out'' signaling, integrins can be switched from an inactive to an active conformation by cytoplasmic signaling molecules leading to increased integrin affinity for the ECM.During 2D migration of adherent cells, nascent, highly dynamic focal contacts are formed at the leading edge lamellipodia where integrins mediate adhesion to the ECM. Some of these focal contacts disassemble and some mature into larger focal adhesions with a longer half-life. Failure in maintaining a dynamic assembly and disassembly of focal contacts will result in the inhibition of cell migration.Integrin-mediated adhesion can be regulated at different levels: (1) by changing integrin conformation and thus affinity for their ligand; (2) by modulating integrin avidity, i.e., by promoting integrin clustering on the plasma membrane; and (3) by changing the kinetics of integrin endocytosis and/or recycling³.The Ras GTPase R-Ras is primarily expressed in the vascular system (endothelial cells and vascular smooth muscle cells)⁴. Zhang et al.⁵ were the first to show that R-Ras is a potent regulator of cell adhesion when they reported that expression of active R-Ras was enough to induce ECM adhesion of suspension cells, whereas dominant negative R-Ras reduced adhesion of the adherent cell line CHO. Although R-Ras was shown to enhance integrin affinity⁵, this effect was not consistently observed^6,7. These contradictory findings could be explained by the fact that R-Ras may activate integrins indirectly through antagonizing H-Ras-mediated integrin inhibition⁶.Recent findings suggest that R-Ras stimulates adhesion through the regulation of integrin internalization into Rab11-positive endosomes⁸. Now, the data of Sandri et al.² support this model. The authors addressed the question on how R-Ras regulates cell adhesion of endothelial cells by performing a yeast-two-hybrid screen using constitutively-active R-Ras as bait. The screen revealed that RIN2 is a major R-Ras-interacting protein. RIN proteins (RIN1, 2 and 3) are downstream effectors of Ras GTPases that function as GEFs for Rab5⁹, a GTPase that regulates endocytosis. RIN1 was shown to mediate the stimulation of EGF receptor-mediated endocytosis by H-Ras through the activation of Rab5¹⁰. Surprisingly, Sandri et al. found that R-Ras dramatically impaired the Rab5 exchange activity of RIN2, while H-Ras had no effect. However, RIN2 was still able to specifically bind active Rab5. These data suggest that active R-Ras, RIN2 and active Rab5 form a signaling complex. Accordingly, Sandri et al. show that endogenous R-Ras, RIN2 and Rab5 are indeed found in a complex in endothelial cells. While active R-Ras and RIN2 colocalize at nascent focal contacts and on intracellular vesicles, colocalization with Rab5 takes place on endosomes. The deletion of either the Ras- or the Rab5-binding domains of RIN2 prevented the colocalization of the trio. Thus, RIN2 appears to facilitate the transport of active R-Ras to Rab5-positive endosomes. What is the functional relevance of these interactions? Sandri et al. show that silencing of endogenous RIN2 impaired the increase in adhesion induced by active R-Ras and by Rab5. A similar effect was obtained upon expression of RIN2 deletion mutants lacking Ras- or Rab5-binding domains. These data strongly suggest that the adaptor function of RIN2 in connecting R-Ras and Rab5 regulates endothelial cell adhesion to the ECM. But what is the mechanism? Previous work has shown that the pro-adhesive activity of active R-Ras is linked to its ability to regulate β1 integrin endocytosis⁸. Sandri et al. confirm these data by showing that silencing of R-Ras or RIN2 decreases the rate of endocytosis of active ECM-engaged β1 integrins. In addition, the authors set a step further as they show that the signaling complex R-Ras/RIN2/Rab5 mediates basal Rac1 GTPase activation. Rac1 regulates actin dynamics and ruffle formation at the leading edge of migrating cells and its activity is essential for cell adhesion and migration. TIAM-1-mediated activation of Rac1 on endosomes and subsequent polarized transport to the plasma membrane has been proposed as a way to restrict Rac activity to sites of membrane protrusion^11,12. In line with this model, Sandri et al. show that active R-Ras and RIN2 colocalize with Rac1 on endosomes and that the endosomal Rac GEF TIAM-1 is necessary for R-Ras- and RIN2-induced cell adhesion.Altogether, the data of Sandri et al. support a model in which, integrin-activated R-Ras recruits RIN2 to focal adhesions and induces RIN2 conversion from a Rab5 GEF to a Rab5-docking protein. Subsequently, the complex promotes the endocytosis of ECM-engaged integrins and moves to early endosomes where R-Ras activates the TIAM-1/Rac1 pathway¹³. Active Rac1 translocates to the plasma membrane where it promotes actin polymerization and formation of new focal contacts (Figure 1).Open in a separate windowFigure 1Model proposed by Sandri et al.² for the regulation of focal adhesion dynamics by R-Ras. (1) R-Ras is activated by ECM-engaged integrins, recruits RIN2 and converts it from a Rab5 GEF to a Rab5 adaptor; (2) RIN2 binding to active Rab5 mediates the endocytosis of integrins and the transport of active R-Ras to endosomes; (3) R-Ras contributes to the activation of the Rac1 GEF TIAM-1, which then activates Rac1; (4) Active Rac1 translocates to the plasma membrane and promotes actin polymerization and formation of new focal contacts.By bridging active R-Ras and Rab5, RIN2 combines two processes essential for cell adhesion: (1) focal contact dynamics through the internalization of ECM-engaged integrins; and (2) local Rac1 activation to ensure actin polymerization at lamellipodia. Similarly, RIN2 also connects H-Ras and Rab5 in the internalization of the epithelial cell-cell adhesion molecule E-cadherin¹⁴. Thus, RIN2 appears to be a universal effector of Ras-induced endocytosis of membrane receptors.Interestingly, the phenotype of a family with a homozygous mutation in RIN2 was recently described¹⁵. The affected individuals showed diverse abnormalities related to a defective connective tissue. Indeed, ultrastructural analysis of the skin showed an abnormal morphology of collagen fibrils. Collagen is a ligand for β1 integrins. Through simultaneous binding to collagen and to the intracellular cytoskeleton, integrins contribute to the assembly of the ECM by transmitting contraction forces from the cell to the ECM. It is tempting to speculate that the phenotype of the patients lacking RIN2 is due to a deficient β1 integrin function as found by Sandri et al. in their in vitro analysis. In addition, these patients bruise easily and present prolonged bleeding, which could be caused by deficient wound healing of blood vessels as a consequence of impaired R-Ras signaling.It should be noted, however, that R-Ras knockout mice have no major defects in vascular development but respond with increased angiogenesis to stress conditions such as tumor implantation⁴. On the contrary, the in vitro study by Sandri et al. suggests that R-Ras deficiency results in decreased endothelial cell migration. Further research is needed to clarify the role of R-Ras in angiogenesis. Likewise, it will be interesting to study vascular responses in RIN2-deficient mice in comparison to R-Ras knockout mice.     

Putting together a plasma membrane NADH oxidase: A tale of three laboratories

The observation that high cellular concentrations of NADH were associated with low adenylate cyclase activity led to a search for the mechanism of the effect. Since cyclase is in the plasma membrane, we considered the membrane might have a site for NADH action, and that NADH might be oxidized at that site. A test for NADH oxidase showed very low activity, which could be increased by adding growth factors. The plasma membrane oxidase was not inhibited by inhibitors of mitochondrial NADH oxidase such as cyanide, rotenone or antimycin. Stimulation of the plasma membrane oxidase by iso-proterenol or triiodothyronine was different from lack of stimulation in endoplasmic reticulum. After 25 years of research, three components of a trans membrane NADH oxidase have been discovered. Flavoprotein NADH coenzyme Q reductases (NADH cytochrome b reductase) on the inside, coenzyme Q in the middle, and a coenzyme Q oxidase on the outside as a terminal oxidase. The external oxidase segment is a copper protein with unique properties in timekeeping, protein disulfide isomerase and endogenous NADH oxidase activity, which affords a mechanism for control of cell growth by the overall NADH oxidase and the remarkable inhibition of oxidase activity and growth of cancer cells by a wide range of anti-tumor drugs. A second trans plasma membrane electron transport system has been found in voltage dependent anion channel (VDAC), which has NADH ferricyanide reductase activity. This activity must be considered in relation to ferricyanide stimulation of growth and increased VDAC antibodies in patients with autism.     

The tale of the three sisters

In this article we present the myocardial deformation imaging (MDI) studies of three daughters of a man with hypertrophic cardiomyopathy (HCM) who died suddenly. The daughters had been referred for genetic counselling several months earlier. We demonstrate that, despite the absence of conventional two-dimensional echo characteristics of HCM, MDI accurately and easily demonstrated the presence of the disease in the two daughters with the genetic disorder. (Neth Heart J 2010;18:452–4.)     

The isolation of Keratinophilic fungi from soils in Israel. A preliminary report

One hundred and fourteen soil samples collected from various areas of Israel were screened for the presence of keratinophilic fungi. Five species were isolated from the 59 positive samples, viz: C. keratinophilum--22 strains, C. evolceanui--18, C. serratus Eidam--10, M. gypseum--T. terrestre--4. Most of the geophilic organisms were recovered from garden soil, road-side and sandy-soil specimens. The importance of these findings is briefly discussed.     

Pigment production by cold-adapted bacteria and fungi: colorful tale of cryosphere with wide range applications

Extremophiles - Pigments are an essential part of everyday life on Earth with rapidly growing industrial and biomedical applications. Synthetic pigments account for a major portion of these...     

Nematophagous fungi: three new species of Myzocytium.

Three species of Myzocytium parasitic on nematodes are described as new. In M. papillatum the zoospores encyst directly on the host cuticle before penetration. This species produces smooth, spherical oospores. In M. glutinosporum the biflagellate zoospores do not attack the host directly; after encystment they produce a spherical adhesive bud which allows the spores to adhere to the cuticle of passing nematodes. This species produces echinulate, spherical oospores. In M. anomalum the primary spores are aplanospores. After a dormant phase, and when suitably stimulated, these aplanospores change into biflagellate zoospores and the latter encyst on the host cuticle. No sexual state is known in this species. Persistence is by means of thick-walled, spherical chlamydospores.     

Tear production in three captive wild herbivores in Israel

The Schirmer tear test (STT) I was performed to evaluate tear production in 12 captive Nubian ibex (Capra ibex nubiana), 10 captive Burchell's zebras (Equus burchelli) and five Arabian oryx (Oryx leucoryx) at the Tel-Aviv Ramat-Gan Zoological Center (Israel). Mean (+/- standard deviation) STT values were 13.2 +/- 5.1 mm/min in the ibex, 23.4 +/- 3.4 mm/min in the zebra and 12.7 +/- 4.8 mm/min in the oryx. There were no significant effects of gender, age, weight, or side of the eye. There were no significant differences in STT values between ibex and oryx, but tear production in both species was significantly lower than in zebras. Knowledge of normal tear production values is important for the differential diagnosis of conjunctivitis and keratitis in these species.