The effect of water activity and pH on the production of mycotoxins by fungi growing on a bread analogue

Mycotoxin production by various toxigenic fungi, growing on a bread analogue, was investigated at various water activities (a_w) and pH combinations. Citrinin, ochratoxin A and sterigmatocystin could be detected at a_w > 0·80, while patulin was only observed at a_w= 0·95. These results show that some toxins may be produced at lower water activities than have been reported on synthetic media and suggest that, where possible, natural substrates should be used to investigate factors affect-ing mycotoxin production in foodstuffs.     

Biology and phylogenetic relationships of Neophonus bruchi, an anomalous south Andean staphylinid (Coleoptera)

Abstract. The virtually unknown monotypic genus Neophonus Fauvel has been collected in several localities in south-central Chile; it was previously known only from the type locality in Argentina. Field observations of the adults on forest foliage and study of their gut contents suggest that they are mycophagous and eat primarily foliicolous fungi, a habit previously unknown in Staphylinidae. Their mouthparts and tarsi show morphological specializations apparently correlated with these habits. Larvae remain unknown. The phylogenetic relationships of the genus within the omaliine-group of Staphylinidae sensu lato are discussed.     

The impact of climate change on the physical characteristics of the larger lakes in the English Lake District

1. The larger lakes of the English Lake District have been the subject of intensive scientific study for more than 60 years. Year‐to‐year variations in the weather have recently been shown to have a major effect on their physical characteristics. The area is mild but very wet and the dynamics of the lakes are strongly influenced by the movement of weather systems across the Atlantic. 2. Here, we combine the results of long‐term measurements and the projections from a Regional Climate Model (RCM) to assess the potential impact of climate change on the surface temperature and residence times of the lakes. 3. The RCM outputs used were produced by the U.K. Hadley Centre and are based on the IPCC ‘A2’ scenario for the emission of greenhouse gases. These suggest that winters in the area will be very much milder and wetter by the 2050s and that there will be a pronounced reduction in the summer rainfall. 4. An analysis of the meteorological data acquired between 1940 and 2000 shows that there have been progressive increases in the winter air temperature and in the rainfall which are correlated with the long‐term change in the North Atlantic Oscillation. The trends reported during the summer were less pronounced and were correlated with the increased frequency of anticyclonic days and a decrease in the frequency of westerly days in the British Isles. 5. A simple model of the year‐to‐year variations in surface temperatures showed that the highest winter temperatures were recorded in the deeper lakes and the highest summer temperatures in the lakes with the shallowest thermoclines. When this model was used to predict the surface temperatures of the lakes in the 2050s, the greatest winter increase (+1.08 °C) was observed in the shallowest lake and the greatest summer increase (+2.18 °C) in the lake with the shallowest thermocline. 6. The model used to estimate the seasonal variation in the residence time of the lakes showed that the most pronounced variations were recorded in lakes with a short residence time. Average winter residence times ranged from a minimum of 10 days to a maximum of 436 days and average summer values from a minimum of 23 days to a maximum of 215 days. When this model was used to predict the residence time of the lakes in the 2050s, the greatest winter decrease (−20%) was observed in the smallest lake and the greatest summer increase (+92%) in the lake with the shortest residence time. 7. The results are discussed in relation to trends reported elsewhere in Europe and the impact of changes in the atmospheric circulation on the dynamics of the lakes. The most serious limnological effects were those projected for the summer and included a general increase in the stability of the lakes and a decrease in the flushing rate of the lakes with short residence times.     

Ion Transport and the Effects of Acetic Acid in White Clover: I. PHOSPHATE ABSORPTION

Dunlop, J., Knighton, M. V. and White, D. W. R. 1988. Ion transportand the effects of acetic acid in white clover. I. Phosphateabsorption.—J. exp. Bot. 39: 79–88. The effect of acetic acid on phosphate absorption by white clovertissue has been examined. At 1·0 mol m³ acetic acid phosphateabsorption by roots of intact plants was stimulated by 36% (P< 0.001). At 5.0 and 10 mol m^–3 acetic acid there wasmarked inhibition of absorption by both suspension culturesof cells and the roots of intact plants. The inhibition waspH dependent with decreasing pH causing increased inhibition.Acetic acid caused changes in the membrane electropotential(E) with concentrations of 2·0 mol m^–3 or lesscausing persistent polarization whereas at 5·0 mol m^–3and higher concentrations the polarization was followed by agreater depolarization. Intracellular pH as measured by thefluorescence of fluorescein was lowered by acetic acid. Calculationsindicate that for white clover roots the proton motive force(pmf) appears to provide sufficient energy for phosphate absorption.It is proposed that acetic acid influences phosphate absorptionthrough its dependence on proton cotransport and that changesin J E affect the rate of phosphate absorption because of thedependence of the pmf on E. Key words: Phosphate absorption, intracellular pH, acetic acid, proton motive force, Trifolium repens, membrane electropotential     

Ion Transport and the Effects of Acetic Acid in White Clover: II. POTASSIUM ABSORPTION

Dunlop, J., Knighton, M. V. and White, D. W. R. 1988. Ion transportand the effects of acetic acid in white clover. II. Potassiumabsorption.—J. exp. Bot. 39: 89–96. Acetic acid stimulated K⁺ influx into cells of white cloverin suspension culture and net K⁺ influx by roots of intact whiteclover plants. At concentrations of acetic acid up to 2·0mol m^–3 the stimulation continued unabated for at least2 h. However, at higher concentrations the rate of absorptiondeclined to near zero values after 2 h. When acetic acid wasremoved from the solution there was a net efflux of K⁺. Thestimulation was pH dependent with a maximum at pH 5·0.There was maximum stimulation at an acetic acid concentrationof 2·0 mol m^–3 Net H⁺ efflux was reduced by 1·0 mol m^–3 aceticacid. When Rb⁺ uptake and H⁺ efflux were measured at a rangeof RbCl concentrations Rb⁺ uptake increased with concentrationwhereas H⁺ efflux was maximum in the absence of Rb⁺ (and K⁺)and decreased as RbCl concentration was increased Acetic acid caused a hyperpolarization of the membrane electricalpotential difference (E) of about 25 mV. In 1·0 mol m^–3acetic acid the hyperpolarization persisted for at least 2 hwhereas at 10 mol m^–3 d E subsequently depolarized tovalues around –80 mV. With a slight lag, the time courseof the stimulation of the rate of K⁺ absorption followed thepolarization and depolarization of E. These results imply thatthe linkage between K⁺ and H⁺ movements is probably throughE. Key words: Proton efflux, membrane electrical potential difference, Trifolium repens     

The influence of water on the resistance of spores to inactivation by gaseous ethylene oxide

Standardized conditions for exposure to ethylene oxide were used to evaluate the resistance of spores dried for various times at different relative humidities and temperatures. Spores dried under conditions of high humidity exhibited low resistance to the sterilant, the resistance increasing as the relative humidity (RH) was decreased. Increasing the temperature of drying amplified this effect by reducing the time required for equilibration to a specific RH. Spores dried over a desiccant at 37°C showed a slight rise followed by a fall in resistance. Spores maintained under these conditions for a long period of time increased in resistance. Spores rapidly dried by exposure to low RH, over a desiccant or at elevated temperature, dried unevenly resulting in a heterogeneous population with respect to ethylene oxide resistance. This was expressed as non-logarithmic survivor curves. The initial vacuum drawn influences resistance. The resistance of spores dried on aluminium foil increased as the pressure was reduced. The rate at which the pressure was reduced had little effect on resistance, except with highly desiccated spores. Dried spores held at different reduced pressures with humidification, showed no differences in resistance. The implications of these findings in relation to the operation of ethylene oxide sterilization cycles and the preparation and use of biological monitors is discussed.     

Studies on the Ship-fouling Alga Enteromorpha II. The Effect of Certain Enzymes on the Adhesion of Zoospores

A method for assessing the adhesion of settled zoospores ofEnteromorpha intestinalis is described. Using this method, the effect of certain enzymes on the attachmentprocess has been studied and the biochemical nature of the secretedadhesive inferred from the results. Although considerable variation in adhesive ability has beenshown to exist between spores from different parent sourcescertain enzymes produce a consistent weakening action on adhesion.Trypsin, pronase, and a-amylase are especially active in thisrespect. The experimental results demonstrate that the -amylaseeffect, although not quite so great as that of the two proteolyticenzymes is, however, genuine. In conjunction with the previous paper it has been shown thatadhesive production is a rapid process, completed within minutesof initial contact and that at this early stage the adhesivematerial is particularly susceptible to proteolytic attack. The results offer the possibility of a biological method forthe control of algal fouling.     

A revision of the marine algae of São Tomé and Principe (Gulf of Guinea)

In all 101 species and varieties of marine algae are mentioned for S. Tomé and Príncipe. These records arise from examination of the material in the herbarium of the Botanical Institute of the University of Coimbra, together with material collected in 1956 by Dr C. A. Thorold. From the latter material there are 17 new records for the island of S. Tomé.
No new species have been described, but Acantkophora ramulosa Kütz. is emended, and Bryopsis densa Pilger and Struvea multipartita Pilger are reduced to the synonymy of Bryopsis pennata var. secunda and Struvea anastomosans respectively.
Information on the climate and tides of the islands is given, and a series of 'seasonal coincidences' likely to influence coastal marine conditions is described for the Gulf of Guinea.     

STUDIES ON PLANT CUTICLE: THE CUTIN COMPONENT OF THE CUTICLES OF LEAVES

Methods are described for the chemical separation from leaf material of the ventral and dorsal surface cuticular membranes and for the determination of cutin in the membranes and leaf tissues.
The cutin contents of the cuticular membranes separated from leaves of laurel, rhododendron, and Euonymus , and of leaf tissues of cauliflower, red beet, banana, tomato, strawberry and blackcurrant are reported. The relationship between the cutin and waxy components of the leaf cuticle is discussed, and earlier work on the development, structure and chemistry of the cuticle is reviewed.