Stimulation of the cyanide-resistant alternative respiratory pathway by oxygen in Acremonium chrysogenum correlates with the size of the intracellular peroxide pool

The relationship between oxygen input and activity of the cyanide-resistant alternative respiration of submerged cultures of Acremonium crysogenum was investigated. The volumetric oxygen transfer coefficient of the respective cultures correlated positively within almost two ranges of magnitude with the size of the intracellular peroxide pool, which in turn, correlated with the activity of the cyanide-resistant alternative respiratory pathway. Increased aeration also stimulated the glucose uptake rate but had no effect on the total respiration rate or the growth rate. Addition of the lipid peroxyl radical scavenger DL-alpha-tocopherol to A. chrysogenum cultures decreased the rate of intracellular peroxide production as well as glucose uptake. An increase in the cyanide-resistant fraction of total respiration was observed, while growth and the total respiratory activity remained unchanged. We conclude that intracellular peroxides may stimulate the alternative respiration in A. chrysogenum.     

Ultrastructural analysis of nematocyte removal in Hydra

A consecutive series of ultrathin sections through the distal one-third of a Hydra tentacle has revealed at least four categories of nematocytes: (1) normal, mounted nematocytes, in specific arrangements within the battery cells; (2) degenerating nematocytes, within the battery cells; (3) mature nematocytes, enclosed within endodermal cells; (4) a mature nematocyte, in the enteric cavity. The degenerating nematocytes within the battery cells and the nematocytes in the endoderm and enteric cavity appeared to be aging nematocytes undergoing death and removal. The results provide the first ultrastructural evidence for nematocyte degeneration within battery cells and also suggest phagocytosis of mature nematocytes by endodermal cells.     

Effects of Blood Glutamate Scavenging on Cortical Evoked Potentials

It is well known that traumatic or ischemic brain injury is followed by acute excitotoxicity caused by the presence of abnormally high glutamate (Glu) in brain fluids. It has recently been demonstrated that excess Glu can be eliminated from brain into blood following the intravenous administration of oxaloacetate (OxAc), which, by scavenging blood Glu, induces an enhanced and neuroprotective brain-to-blood Glu efflux. In this study, we subjected rats to intravenous OxAc administration (i.v., 12.5, 25, and 50 mg/kg, respectively), and studied its effects on somatosensory evoked cortical potentials (EPs). Against our expectation, the amplitudes of EPs did not decrease but increased in a dose- and time-dependent manner after OxAc administration. Similar effects were observed when blood Glu scavenging was enhanced by combining OxAc (12.5 mg/kgbw) with recombinant glutamate–oxaloacetate transaminase (GOT, 0.14 nmol/100 g rat). On the basis of these results, we suggest that the changes of amplitudes of the EPs involve not only a glutamatergic but also the weakening of a GABAergic component. We cannot rule out the possibility that OxAc penetrates into the brain and improves mitochondrial functions.     

Temporal isolation explains host-related genetic differentiation in a group of widespread mycoparasitic fungi

Understanding the mechanisms responsible for divergence and specialization of pathogens on different hosts is of fundamental importance, especially in the context of the emergence of new diseases via host shifts. Temporal isolation has been reported in a few plants and parasites, but is probably one of the least studied speciation processes. We studied whether temporal isolation could be responsible for the maintenance of genetic differentiation among sympatric populations of Ampelomyces, widespread intracellular mycoparasites of powdery mildew fungi, themselves plant pathogens. The timing of transmission of Ampelomyces depends on the life cycles of the powdery mildew species they parasitize. Internal transcribed spacer sequences and microsatellite markers showed that Ampelomyces populations found in apple powdery mildew (Podosphaera leucotricha) were genetically highly differentiated from other Ampelomyces populations sampled from several other powdery mildew species across Europe, infecting plant hosts other than apple. While P. leucotricha starts its life cycle early in spring, and the main apple powdery mildew epidemics occur before summer, the fungal hosts of the other Ampelomyces cause epidemics mainly in summer and autumn. When two powdery mildew species were experimentally exposed to Ampelomyces strains naturally occurring in P. leucotricha in spring, and to strains naturally present in other mycohost species in autumn, cross‐infections always occurred. Thus, the host‐related genetic differentiation in Ampelomyces cannot be explained by narrow physiological specialization, because Ampelomyces were able to infect powdery mildew species they were unlikely to have encountered in nature, but instead appears to result from temporal isolation.     

Optimization of diagnostic microarray for application in analysing landfill methanotroph communities under different plant covers

Landfill sites are responsible for 6-12% of global methane emission. Methanotrophs play a very important role in decreasing landfill site methane emissions. We investigated the methane oxidation capacity and methanotroph diversity in lysimeters simulating landfill sites with different plant vegetations. Methane oxidation rates were 35 g methane m-2 day-1 or higher for planted lysimeters and 18 g methane m-2 day-1 or less for bare soil controls. Best methane oxidation, as displayed by gas depth profiles, was found under a vegetation of grass and alfalfa. Methanotroph communities were analysed at high throughput and resolution using a microbial diagnostic microarray targeting the particulate methane monooxygenase (pmoA) gene of methanotrophs and functionally related bacteria. Members of the genera Methylocystis and Methylocaldum were found to be the dominant members in landfill site simulating lysimeters. Soil bacterial communities in biogas free control lysimeters, which were less abundant in methanotrophs, were dominated by Methylocaldum. Type Ia methanotrophs were found only in the top layers of bare soil lysimeters with relatively high oxygen and low methane concentrations. A competetive advantage of type II methanotrophs over type Ia methanotrophs was indicated under all plant covers investigated. Analysis of average and individual results from parallel samples was used to identify general trends and variations in methanotroph community structures in relation to depth, methane supply and plant cover. The applicability of the technology for the detection of environmental perturbations was proven by an erroneous result, where an unexpected community composition detected with the microarray indicated a potential gas leakage in the lysimeter being investigated.     

Flowers for better pest control? The effects of apple orchard ground cover management on green apple aphids (Aphis spp.) (Hemiptera: Aphididae), their predators and the canopy insect community

Effects of habitat diversification through ground cover management on green apple aphids (Aphis spp.) (Hemiptera: Aphididae), woolly apple aphid (Eriosoma lanigerum [Haussmann]) (Hemiptera: Aphididae), their insect natural enemies and the most abundant canopy insects (in the Neuroptera, Fulgoromorpha, Cicadomorpha, Heteroptera, Coleoptera and Formicidae) were studied in an apple orchard over 6 years. The composition and diversity of the main functional groups of canopy insects was also compared. Habitat diversification was achieved by changing ground cover conditions within the orchard. In the treatment termed FLOWER, annual and/or perennial flowering plants were sown in the alleys of an apple orchard. Other ground cover treatments were weed-free bare ground (termed BAREgr) and orchard plots with alleys of mowed grass (termed GRASS), which served as control treatments. We found no evidence that habitat diversification enhanced the biological control of green apple aphids compared to the control treatments. However, the greater plant cover in FLOWER resulted in increased woolly apple aphid infestations compared to BAREgr or GRASS. The abundance of various beneficial or neutral canopy insects – Chrysoperla carnea sensu lato (Neuroptera, Chrysopidae) adults, leafhoppers and treehoppers, planthoppers, herbivorous (non-apple feeding) beetles, dipterans and parasitoid wasps – also increased in FLOWER as compared to BAREgr, with GRASS being intermediate between the other treatments. Significantly greater species richness and diversity was found in FLOWER than in BAREgr for most of the functional groups sampled, although the number of predacious insect species was similar among treatments. The composition of the studied functional groups showed high similarity in FLOWER and GRASS, but these treatments were different from BAREgr. Effects of groundcover management on the dominant insect species are discussed.     

Comparison of Botrytis cinerea populations isolated from two open-field cultivated host plants

The necrotrophic fungus Botrytis cinerea is reported to infect more than 220 host plants worldwide. In phylogenetical–taxonomical terms, the pathogen is considered a complex of two cryptic species, group I and group II. We sampled populations of B. cinerea on sympatric strawberry and raspberry cultivars in the North-East of Hungary for three years during flowering and the harvest period. Four hundred and ninety group II B. cinerea isolates were analyzed for the current study. Three different data sets were generated: (i) PCR-RFLP patterns of the ADP-ATP translocase and nitrate reductase genes, (ii) MSB1 minisatellite sequence data, and (iii) the fragment sizes of five microsatellite loci. The structures of the different populations were similar as indicated by Nei's gene diversity and haplotype diversity. The F statistics (F_st, G_st), and the gene flow indicated ongoing differentiation within sympatric populations. The population genetic parameters were influenced by polymorphisms within the three data sets as assessed using Bayesian algorithms. Data Mining analysis pointed towards the five microsatellite loci as the most defining markers to study differentiation in the 490 isolates. The results suggest the occurrence of host-specific, sympatric divergence of generalist phytoparasites in perennial hosts.     

Understanding the Role of Cesium and Rubidium Additives in Perovskite Solar Cells: Trap States,Charge Transport,and Recombination

Adding cesium (Cs) and rubidium (Rb) cations to FA_0.83MA_0.17Pb(I_0.83Br_0.17)₃ hybrid lead halide perovskites results in a remarkable improvement in solar cell performance, but the origin of the enhancement has not been fully understood yet. In this work, time‐of‐flight, time‐resolved microwave conductivity, and thermally stimulated current measurements are performed to elucidate the impact of the inorganic cation additives on the trap landscape and charge transport properties within perovskite solar cells. These complementary techniques allow for the assessment of both local features within the perovskite crystals and macroscopic properties of films and full devices. Strikingly, Cs‐incorporation is shown to reduce the trap density and charge recombination rates in the perovskite layer. This is consistent with the significant improvements in the open‐circuit voltage and fill factor of Cs‐containing devices. By comparison, Rb‐addition results in an increased charge carrier mobility, which is accompanied by a minor increase in device efficiency and reduced current–voltage hysteresis. By mixing Cs and Rb in quadruple cation (Cs‐Rb‐FA‐MA) perovskites, the advantages of both inorganic cations can be combined. This study provides valuable insights into the role of these additives in multiple‐cation perovskite solar cells, which are essential for the design of high‐performance devices.