Observations on the introduction of Verticillium chlamydosporium and other parasitic fungi into soil for control of the cereal cyst-nematode Heterodera avenue

Isolates of Verticillium chlamydosporium and a sterile fungus added to soil on ground oat grain reduced the numbers of Heterodera avenae on wheat by between 26 and 80%. Nematode populations in uninoculated soil increased from 15 eggs/g soil before planting to 218 eggs/g after harvest. V. chlamydosporium was isolated from oat grain that had been air-dried and milled before introduction into soil. Applications of the fungi on attapulgite clay or as suspensions of mycelium and spores in water had no effect on nematode multiplication. The effect of the fungi on numbers of H. avenae eggs was similar in autoclaved and non-sterilised soil. V. chlamydosporium added on attapulgite clay to a calcareous sand and a calcareous silty loam could be re-isolated after at least 6 months. Some isolates colonised the roots of wheat without causing lesions or affecting the dry weights of shoots or roots. These results indicate that V. chlamydosporium may be useful for the biological control of cyst nematode pests.     

H+ V-ATPases Energize Animal Plasma Membranes for Secretion and Absorption of Ions and Fluids

SYNOPSIS. H⁺ V-ATPases are well known energizers of endomembranes;thus they play a key role in the acidification of vacuoles andvesicles. More recently it has become clear that they energizemany plasma membranes as well. In epithelial cells H⁺ V-ATPasesusually energize apical plasma membranes in the same sense thatNa⁺/K⁺ P-ATPases usually energize basolateral plasma membranes.Examples of four fundamental processes so energized will bereviewed—Na⁺ and Cl^– absorption by the frog skin,K⁺ secretion by the caterpillar midgut, fluid secretion by insectMalpighian tubules, and fluid absorption by insect ovarian folliclecells. It is likely that apical membranes of fresh water fishand other animals that live in media in which the concentrationof Na⁺ is low, are also energized by H⁺ V^– ATPases.     

Alterations in growth of tissue-cultured tansy (Tanacetum vulgare L.) treated with antibiotics

Effects of three antibiotics (cefotaxime, rifampicin and gentamicin) were tested on in vitro shoots cultures of tansy (Tanacetum vulgare L.)- These antibiotics were selected because endophytic bacteria isolated from the in vitro shoot cultures of tansy showed that all bacteria were Gram-negative and their growth was reduced by these three antibiotics. Five isolates were Enterobacteriaceae, three were fluorescent Pseudomonas, and two were aerobic bacteria. Increased concentrations of antibiotics caused usually linear or quadratic changes on the initiation of shoot growth, shoot number, growth rate, and shoot height. These changes and changes in pH of the culture media were tansy genotype-dependent following treatments with gentamicin. Also, the treatment with rifampicin or cefotaxime showed a genotype-dependent effect, because they resulted in significantly higher percentage of rooted plants in one of the three tansy genotypes tested. The growth rate and length of shoots were reduced in the media containing both gentamicin and rifampicin, but less so than in media containing both gentamicin and cefotaxime.     

The construction of recA–deficient Rhizobium meliloti and R. leguminosarum strains marked with gusA or luc cassettes for use in risk–assessment studies

A vector system was developed employing the recA genes of Rhizobium meliloti and Rhizobium leguminosarum biovar. viciae as target sequences for the stable genomic integration of foreign DNA. The plasmid vectors can be used either as integration vectors (single cross–over), or as gene replacement vectors (double cross–over). Gene replacement results in the antibiotic–marker–free integration of cloned DNA into the recA genes of R. meliloti and R. leguminosarum bv. viciae. Consequently, the recombinant strains become recombination deficient (RecA^-). The expression of integrated genes is under the control of the neomycin phosphotransferase II (nptll) promoter of transposon Tn5. The system was used to construct recA mutant strains of R. meliloti and R. leguminosarum by. viciae, carrying the Escherichia coli gusA gene encoding β–glucuronidase as well as the firefly (Photinus pyralis) luc gene encoding luciferase as marker genes. The GUS activity in the constructed strains was found to be absolutely stable over more than 100 generations of non–selective growth in liquid culture. The stability was also confirmed in root–nodule passages. In addition, the potential use of the luc gene as a stable genetic marker in the unequivocal identification of tagged strains among indigenous microbes in non–sterile soil was demonstrated. It is proposed to use bioluminescent recA mutants as model organisms in risk assessment studies with genetically engineered Rhizobium strains.     

A quantitative study of mortality at emergence in the damselfly Pyrrhosoma nymphula (Sulzer) (Zygoptera: Coenagrionidae)

SUMMARY.

• 1 Emergence of the damselfly Pyrrhosoma nymphula was studied over three seasons in two ponds in northern England.
• 2 Numbers emerging were significantly negatively correlated with temperature and atmospheric pressure.
• 3 Overall mortality at emergence was 28%. of which predators (largely birds, ants and spiders) accounted for 22% and climatic factors 6%.
• 4 Daily mortality estimates were significantly positively correlated with precipitation.
• 5 There was no evidence of density dependent mortality at emergence.

     

The distribution of micro-arthropods in some southern English streams: the influence of physicochemistry

SUMMARY. 1. Micro-arthropods were surveyed during October 1986 at thirty stony, stream riffle sites in the Ashdown Forest, southern England.
2. The importance of a number of physicochemical variables in determining both the distribution of micro-arthropod taxa and community structure was assessed.
3. Acidic sites had an impoverished fauna. Total micro-arthropod species richness and densities were highest under circumneutral conditions. and the same patterns were shown by the Hydrachnellae, Harpucticoida and Cladocera. A number of species seemed indifferent to acidic conditions and were widespread and, as a group, the cyclopoid copepods showed no relationship with pH.
4. Multiple regression showed that other environmental variables, in particular annual mean temperature and maximum discharge, were also important in explaining the between-site distribution of separate micro-arthropod groups and individual species.
5. Other multivariate techniques (ordination, classification and multiple discriminant analysis) showed that impoundment linkage, source distance and conductivity, along with pH, were the most important variables in explaining patterns of species composition between sites.     

Enzymes of Carbohydrate Metabolism in Four Human Species of Leishmania: A Comparative Survey*

SYNOPSIS. The occurrence and levels of activity of various enzymes of carbohydrate catabolism in culture forms (promastigotes) of 4 human species of Leishmania (L. brasiliensis, L. donovani, L. mexicana, and L. tropica) were compared. These organisms possess enzymes of the Embden-Meyerhof pathway but lack lactate dehydrogenase. No evidence could be found for the production of lactic acid by growing cultures and lactic acid could not be detected either in cell-free preparations or after incubation of cell-free extracts with pyruvate and NADH under appropriate conditions. All 4 species possess α-glycerophosphate dehydrogenase and α-glycerophosphate phosphatase which together could regenerate NAD, thus compensating for the absence of lactate dehydrogenase. The oxidative and nonoxidative reactions of the hexose monophosphate pathway are present in all 4 species. Cell-free extracts have pyruvate dehydrogenase activity which allows the entry of pyruvate into and its subsequent oxidation through the tricarboxylic acid cycle. All enzymes of this cycle, including a thiamine pyrophosphate dependent α-ketoglutarate dehydrogenase are present. Both NAD and NADP-linked malate dehydrogenase activities are present. The isocitrate dehydrogenase is NADP specific. There is an active glutamate dehydrogenase which could compete with α-ketoglutarate dehydrogenase for the common substrate (α-ketoglutarate). Replenishment of C₄ acids is accomplished by heterotrophic CO₂ fixation catalyzed by pyruvate carboxylase. All 4 species have high levels of NADH oxidase activity. Several enzymes thus far not found in any species of Leishmania have been demonstrated. These are: phosphoglucose isomerase, triose phosphate isomerase, fructose-1, 6-diphosphatase, 3-phosphoglycerate kinase, enolase, α-glycerophosphate dehydrogenase, α-glycerophosphate phosphatase, pyruvate dehydrogenase complex, citrate synthase, aconitase, α-ketoglutarate dehydrogenase, glutamate dehydrogenase, and NADH oxidase.     

Dinitrocresol, Cyanide, and the Pasteur Effect in Yeast

At pH 5·0 the respiration of yeast is stimulated by lowconcentrations of 3:5-dinitro-o-cresol, reaching a peak levelof 170 per cent, at 10⁵ M. Concentrations above this inhibitoxygen uptake and cause aerobic fermentation to appear, whichin turn reaches a peak value and is then inhibited. The rateof carbohydrate breakdown, or glycolysis, calculated from therates of respiration and aerobic fermentation, increases steadilyup to 3 x 10^–5 M., at which concentration it is 5 timesfaster than the control: higher concentrations depress the rateof glycolysis. The rate of fermentation under nitrogen is abouttwice that of respiration, and it is inhibited over the sameconcentration range as aerobic fermentation. It was found earlier that oxidative assimilation of glucoseby yeast is progressively inhibited by increasing concentrationsof dinitrocresol, and it is now shown that this parallels theincrease in the rate of aerobic glycolysis. It is argued thatdinitrocresol is here acting as an uncoupling agent and thatboth oxidative assimilation and the rate of glycolysis are controlledby the level of energy-rich phosphate. With cyanide there is no stimulation of oxygen uptake, aerobicfermentation only appears when respiration becomes inhibited,and after an initial slight decrease the rate of glycolysisrises to 575 per cent. of the control value at 5 x 10^–4M. It is suggested that the rate of glycolysis only increaseswhen respiration has been inhibited sufficiently to reduce therate of formation of energy-rich phosphate.     

Host plant effects on the performance of the aphid Aulacorthum solani (Kalt.) (Homoptera: Aphididae) at ambient and elevated CO2

In future elevated CO₂ environments, chewing insects are likely to perform less well than at present because of the effects of increased carbon fixation on their host plants. When the aphid, Aulacorthum solani was reared on bean ( Vicia faba ) and tansy ( Tanacetum vulgare ) plants under ambient and elevated CO_2, performance was enhanced on both hosts at elevated CO₂. The nature of the response was different on each plant species suggesting that feeding strategy may influence an insect's response to elevated CO₂. On bean, the daily rate of production of nymphs was increased by 16% but there was no difference in development time, whereas on tansy, development time was 10% shorter at elevated CO₂ but the rate of production of nymphs was not affected. The same aphid clone therefore responded differently to elevated CO₂ on different host plants. This increase in aphid performance could lead to larger populations of aphids in a future elevated CO₂ environment.