A Fungal Parasite of Meloidogyne javanica Eggs: Evaluation of its Use to Control the Root-knot Nematode

A fungal parasite was isolated from black - coloured egg masses of Meloidogyne javanica on tomato roots . The fungus did not sporulate on any of the culture media tested or in the egg mass . Hyphal characteristics suggest that it is similar to the hyphomycete genus Scytalidium. Hyphae of the Scytalidium- like fungus (CBS 645 . 97 and IMI 368886) proliferated in the gelatinous matrix of the egg mass and penetrated the eggshell via a penetration peg . Parasitism of the egg mass greatly lowered the hatch rate of M. javanica juveniles in vitro. Application of the fungus to soil did not inhibit juvenile penetration into tomato roots . However , the nematode population in soil treated with the fungus was lower than in non - treated soil after one nematode generation . The exact identification of the Scytalidium like fungus , technology for mass production and its application in the field for control of root - knot nematodes requires further investigation .     

The Effects of Rhythmicity and Amplitude on Transfer of Motor Learning

We perform rhythmic and discrete arm movements on a daily basis, yet the motor control literature is not conclusive regarding the mechanisms controlling these movements; does a single mechanism generate both movement types, or are they controlled by separate mechanisms? A recent study reported partial asymmetric transfer of learning from discrete movements to rhythmic movements. Other studies have shown transfer of learning between large-amplitude to small-amplitude movements. The goal of this study is to explore which aspect is important for learning to be transferred from one type of movement to another: rhythmicity, amplitude or both. We propose two hypotheses: (1) Rhythmic and discrete movements are generated by different mechanisms; therefore we expect to see a partial or no transfer of learning between the two types of movements; (2) Within each movement type (rhythmic/discrete), there will be asymmetric transition of learning from larger movements to smaller ones. We used a learning-transfer paradigm, in which 70 participants performed flexion/extension movements with their forearm, and switched between types of movement, which differed in amplitude and/or rhythmicity. We found partial transfer of learning between discrete and rhythmic movements, and an asymmetric transfer of learning from larger movements to smaller movements (within the same type of movement). Our findings suggest that there are two different mechanisms underlying the generation of rhythmic and discrete arm movements, and that practicing on larger movements helps perform smaller movements; the latter finding might have implications for rehabilitation.     

Evidence of natural Wolbachia infections and molecular identification of field populations of Culex pipiens complex (Diptera: Culicidae) mosquitoes in western Turkey

Establishing reliable risk projection information about the distribution pattern of members of the Culex pipiens complex is of particular interest, as these mosquitoes are competent vectors for certain disease‐causing pathogens. Wolbachia, a maternally inherited bacterial symbiont, are distributed in various arthropod species and can induce cytoplasmic incompatibility, i.e., reduced egg hatch, in certain crosses. It is being considered as a tool for population control of mosquito disease vectors. The Aegean region is characterized by highly populated, rural, and agricultural areas and is also on the route of the migratory birds. In this study, a fragment of the 658 bp of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene, which includes the barcode region, was employed to differentiate Cx. pipiens complex species found in this region. Moreover, for the first time, the prevalence of Wolbachia endobacteria in these natural populations was examined using PCR amplification of a specific wsp gene. Our results revealed a widespread (more than 90%, n=121) presence of the highly efficient West Nile virus vector Cx. quinquefasciatus in the region. We also found that Wolbachia infection is widespread; the average prevalence was 62% in populations throughout the region. This study provided valuable information about the composition of Cx. pipiens complex mosquitoes and the prevalence of Wolbachia infection in these populations in the Aegean region. This information will be helpful in tracking mosquito‐borne diseases and designing and implementing Wolbachia‐based control strategies in the region.     

Modelling species responses to extreme weather provides new insights into constraints on range and likely climate change impacts for Australian mammals

Conservation of species under climate change relies on accurate predictions of species ranges under current and future climate conditions. To date, modelling studies have focused primarily on how changes in long‐term averaged climate conditions are likely to influence species distributions with much less attention paid to the potential effect of extreme events such as droughts and heatwaves which are expected to increase in frequency over coming decades. In this study we explore the benefits of tailoring predictor variables to the specific physiological constraints of species, or groups of species. We show how utilizing spatial predictors of extreme temperature and water availability (heat‐waves and droughts), derived from high‐temporal resolution, long‐term weather records, provides categorically different predictions about the future (2070) distribution of suitable environments for 188 mammal species across different biomes (from arid zones to tropical environments) covering the whole of continental Australia. Models based on long‐term averages‐only and extreme conditions‐only showed similarly high predictive performance tested by hold‐out cross‐validation on current data, and yet some predicted dramatically different future geographic ranges for the same species under 2070 climate scenarios. Our results highlight the importance of accounting for extreme conditions/events by identifying areas in the landscape where species may cope with average conditions, but cannot persist under extreme conditions known or predicted to occur there. Our approach provides an important step toward identifying the location of climate change refuges and danger zones that goes beyond the current standard of extrapolating long‐term climate averages.     

Increased heterologous production of the antitumoral polyketide mithramycin A by engineered Streptomyces lividans TK24 strains

Mithramycin A is an antitumor compound used for treatment of several types of cancer including chronic and acute myeloid leukemia, testicular carcinoma, hypercalcemia and Paget’s disease. Selective modifications of this molecule by combinatorial biosynthesis and biocatalysis opened the possibility to produce mithramycin analogues with improved properties that are currently under preclinical development. The mithramycin A biosynthetic gene cluster from Streptomyces argillaceus ATCC12956 was cloned by transformation assisted recombination in Saccharomyces cerevisiae and heterologous expression in Streptomyces lividans TK24 was evaluated. Mithramycin A was efficiently produced by S. lividans TK24 under standard fermentation conditions. To improve the yield of heterologously produced mithramycin A, a collection of derivative strains of S. lividans TK24 were constructed by sequential deletion of known potentially interfering secondary metabolite gene clusters using a protocol based on the positive selection of double crossover events with blue pigment indigoidine-producing gene. Mithramycin A production was evaluated in these S. lividans strains and substantially improved mithramycin A production was observed depending on the deleted gene clusters. A collection of S. lividans strains suitable for heterologous expression of actinomycetes secondary metabolites were generated and efficient production of mithramycin A with yields close to 3 g/L, under the tested fermentation conditions was achieved using these optimized collection of strains.

     

Histamine catabolism in Pseudomonas putida U: identification of the genes,catabolic enzymes and regulators

In this study, the catabolic pathway required for the degradation of the biogenic amine histamine (Hin) was genetically and biochemically characterized in Pseudomonas putida U. The 11 proteins (HinABCDGHFLIJK) that participate in this pathway are encoded by genes belonging to three loci hin1, hin2 and hin3 and by the gene hinK. The enzymes HinABCD catalyze the transport and oxidative deamination of histamine to 4‐imidazoleacetic acid (ImAA). This reaction is coupled to those of other well‐known enzymatic systems (DadXAR and CoxBA‐C) that ensure both the recovery of the pyruvate required for Hin deamination and the genesis of the energy needed for Hin uptake. The proteins HinGHFLKIJ catalyze the sequential transformation of ImAA to fumaric acid via N₂‐formylisoasparagine, formylaspartic acid and aspartic acid. The identified Hin pathway encompasses all the genes and proteins (transporters, energizing systems, catabolic enzymes and regulators) needed for the biological degradation of Hin. Our work was facilitated by the design and isolation of genetically engineered strains that degrade Hin or ImAA and of mutants that accumulate Ala, Asp and Hin catabolites. The implications of this research with respect to potential biotechnological applications are discussed.     

Rapid sampling of yeast cells and automated assays of adenylate, citrate, pyruvate and glucose-6-phosphate pools

A sampling technique for yeast cells with a very short interval between harvesting and inactivation of the cells is described. HClO₄ serves as inactivating agent. Optimal extraction is achieved by three freeze-thaw cycles of the acidic solution followed by neutralization with 2 m KHCO₃ to pH 7.5. Methods are presented for the automated fluorometric analyses of ATP, ADP, AMP, glucose-6-phosphate, pyruvate and citrate, as well as for the preparation of crude cell extracts.     

Continuous cultivation of Saccharomyces cerevisiae. II. Growth on ethanol under transient-state conditions

Growth of Saccharomyces cerevisiae LBG H 1022 on ethanol under transient-state conditions was studied. As a cultivation device, an aerated Chemap fermentor combined with continuously working gas analyzers for oxygen and carbon dioxide was used. Yeast cell dry matter, substrate concentration, specific oxygen uptake, specific carbon dioxide release, and respiration quotient were measured during the different transient states. Depending on which range of the dilution rate the initial steady state was found, we obtain different responses to the shift experiment. For the lower range, up to D = 0.07, we deal with damped oscillations ranging above and below the steady-state values. For the higher specific growth rates, the rate of damping is strongly enhanced and the shape of the curves becomes an asymptotic approach to the final steady states.     

Effect of calcium restriction on cardenolide accumulation in two cell lines of Digitalis thapsi grown under different light regimes

The effect of calcium-deprivation on growth and the production of cardenolides in two undifferentiated cell lines of Digitalis thapsi maintained under three different light regimes (16 h photoperiod, darkness, or continuous light) was investigated. Growth was stimulated by continuous light in both cell lines cultured in complete medium. The light regime did not affect cardenolide accumulation in the cells of the hypocotyl-derived line; by contrast, continuous light or darkness increased the production in the leaf-derived line. The elimination of calcium favoured cardenolide production independently of the origin of the suspensions and the light regime, this beneficial effect being predominantly manifested under continuous light.